Concrete Calculator
Know how much concrete to order before the truck is booked.
Enter your dimensions for cubic yards, cubic feet and 60lb or 80lb bag counts, with a waste allowance, the cost at your yard price and a line you can drop straight onto an invoice.
- Free, no signup
- Runs in your browser
- Bags, yards and cost
- Waste allowance
Enter concrete dimensions
Project type
Length (ft)
Width (ft)
Thickness (inches)
4 inch typical slab
Waste percent (%)
10 percent standard
Price per cubic yard ($)
Bag size
Labor rate ($ per sq ft or total)
3D preview · drag to rotate 0°
SlabQuick examples for invoices
Your concrete estimate to invoice
$404.00
Total to invoice - $204 concrete + $200 labor
Formula text
Invoice line item template for concrete
Line item
Watch the calculator fill itself in
The same panel you used above, working out a 20 by 12 foot slab at 5 inches: volume, the waste allowance, bag counts and the cost at your yard price, updating as each field is typed.
Your concrete order
0.00 yd³
Cubic yards with waste
yd³ = L × W × T ÷ 27
If the pour grows
Start with the amount you need to borrow
Jump to any part to replay it. The formulas behind these numbers are set out further down the page.
From yardage to an invoice that gets paid
The volume is the easy part of a concrete job. These are the four places the money goes missing between working out the order and being paid for the pour.
Quote the pour, not the concrete
Concrete is rarely half the finished cost. Excavation, hardcore, forms, mesh, labour and the finish are the rest, and a client who was quoted a yard price will argue about every one of them later.
Itemise it once on a written quote and the conversation is over before it starts.
Waste is a cost, not a rounding error
The 10 percent you add for uneven subgrade and what stays in the drum is real money on a large pour. Price it in rather than absorbing it, and note on the quote that surplus concrete cannot be returned once it is batched.
The profit margin calculator checks the job still pays once that is counted.
Access and short loads change the price
A pump, a wheelbarrow run, or a supplier's short-load fee can cost more than the concrete on a small job. They are decisions made before the truck is booked, so they belong on the quote rather than on a surprise invoice.
Say plainly what is included and what triggers an extra charge.
Invoice the day the pour is finished
Concrete is one of the few trades where the work is unmistakably complete: it is either down or it is not. Bill it that day, with the yardage, the finish and the terms on the page.
The invoice generator takes the same lines you quoted, so the two documents agree.
A margin is a decision, not a calculation
The number on this page is only real once it survives the quote, the job and the wait to be paid. These are the three documents that decide whether it does, and the other two are free here as well.
Set the margin
Cost in, margin out, or name the margin you need and take the price it gives you. Check it per line rather than across the whole job.
You are hereQuote at that price
Put the price in writing with what is included, a deposit and a valid-until date, so the figure you calculated is the figure you are held to.
Open the Quote GeneratorInvoice and collect
Bill the day the work is done, with terms, a due date and a stated late fee. Waiting 60 days for payment can cost more than the job earned.
Open the Invoice GeneratorBorrowing to cover the gap between doing the work and being paid? The loan calculator prices that properly, fees included, so you can compare it against simply asking for a deposit.
Why use a concrete calculator instead of doing the maths by hand?
Calculating concrete in Excel misses waste, bag conversion, and shape formulas. Our calculator prevents short ordering and helps you invoice accurately with cubic yards, bags, cost, total. Part of InvoiceTools suite so you can calculate then create invoice directly. All calculations in browser, no data stored, works on job site.
Accurate cubic yards for invoice
Enter the length, width and thickness. The calculator works out cubic feet as length times width times thickness in feet, then cubic yards as cubic feet divided by 27. Example: a 10x10 slab at 4 inches is 33.33 cu ft, or 1.23 cu yd. Add 10 percent waste for spillage and an uneven base.
From estimate to invoice in one click
See concrete cost cu yd with waste times price per yard, labor cost sq ft times rate, total to invoice. Copy invoice line template auto generated with dimensions cu yd bags cost. Paste into InvoiceTools invoice generator.
Unique - Waste, bags, shapes included
Waste 10 percent standard, bag size 80lb 0.6 cu ft 60lb 0.45 cu ft 40lb 0.33 cu ft, shapes slab footing column stairs curb and gutter, price per yard $120 to $200, labor per sq ft $2 to $8. Shows exact vs with waste vs bags.
Built for concrete contractors who invoice
Mobile first works on job site iPhone Android, no app install, client side only. For driveway, patio, sidewalk, foundation, footing, column, curb gutter contractors who invoice concrete jobs and need quick accurate quantity.
How to calculate concrete for slabs, footings, walls and stairs
Every shape uses length, width and depth in feet, then divides by 27 to get cubic yards. Use the calculator above to avoid manual errors, then copy the result to your invoice.
1. Slabs and walls - rectangular
For square or rectangular slabs, square footings, walls, roof slabs. Measure length ft, width ft, thickness or height ft. Thickness 4 inch equals 0.33 ft, 6 inch equals 0.5 ft. Formula cubic yards equals length times width times thickness divided by 27. Example slab 15 ft long 10 ft wide 0.5 ft thick 15 times 10 times 0.5 equals 75 cu ft divided by 27 equals 2.78 cubic yards. Our calculator above does this instantly and shows 80lb and 60lb bags needed for slab quantity. Perfect for quick on site invoices.
Formula: CY = L x W x H(ft) / 27 | Example: 15x10x0.5/27 = 2.78 yd³
2. Circular slabs and post holes - round
For round slabs, circular pads, patios, post holes. Measure radius ft which is diameter divided by 2, and depth ft. Formula cubic yards equals pi times radius squared times depth divided by 27. Pi 3.14. Example circular slab radius 6 ft depth 0.5 ft 3.14 times 36 times 0.5 equals 56.52 cu ft divided by 27 equals 2.09 cubic yards. Use Circular Slabs mode in calculator enter radius and depth get cubic feet cubic yards cubic meters. Ideal for round patio pads or multiple post hole foundations.
Formula: CY = π x r² x Depth / 27 | Example: 3.14x6²x0.5/27 = 2.09 yd³
3. Square and rectangular footings
For deck footings, wall footings, building foundations where structural strength matters. Enter length, width, depth ft into Slabs and Walls setting. Calculator gives cubic feet cubic yards cubic meters instantly useful for multiple footings. Footings use the same rectangular sum as a slab. Example footing 8 ft long 2 ft wide 1.5 ft deep 8 times 2 times 1.5 equals 24 cu ft divided by 27 equals 0.89 cubic yards. Knowing this avoids under or over ordering for stable foundation and accurate invoice.
Formula: CY = L x W x D / 27 | Example: 8x2x1.5/27 = 0.89 yd³
4. Round footings, columns, piers
For round footings for columns, piers, post holes. Exact volume avoids waste. Use Hole Column or Round Footings section enter diameter and depth plus quantity. Tool calculates volume in cu ft cu yd cu m for single or multiple round footings in seconds. Pi x radius squared x depth in feet, divided by 27. Example round footing radius 1.5 ft depth 2 ft 3.14 times 2.25 times 2 equals 14.13 cu ft divided by 27 equals 0.52 cubic yards. Measure radius and depth multiply circle area by depth then convert to cubic yards.
Formula: CY = π x r² x D / 27 | Example: 3.14x1.5²x2/27 = 0.52 yd³
5. Curb and gutter - long and narrow
For curbs, gutters, sidewalks, driveways, parking lots, street edges. These are long narrow runs. Enter curb depth, gutter width, curb height, flag thickness, total length ft into Curb and Gutter section. Calculator returns cu ft cu yd cu m without manual math. Formula cubic yards equals length times width times depth divided by 27 using combined cross section. A 100 foot curb, 1.5 feet wide and half a foot deep, comes to 2.78 cubic yards. Measure length width depth convert to cubic yards to buy right amount for invoice.
Formula: CY = L x W x D / 27 | Example: 100x1.5x0.5/27 = 2.78 yd³
6. Stairs - multiple steps
For concrete stairs, steps, staircase with platform. Enter rise height, run depth, width, number of steps, platform depth. Calculator estimates total volume cu ft cu yd cu m for small sets or full staircases. Formula cubic yards equals number of steps times length times width times height divided by 27 using single step volume times steps. Example 10 steps each 3 ft long 4 ft wide 0.5 ft tall 10 times 3 times 4 times 0.5 equals 60 cu ft divided by 27 equals 2.22 cubic yards. Knowing how to figure concrete for stairs gives safe sturdy staircase and correct invoice quantity.
Formula: CY = Steps x L x W x H / 27 | Example: 10x3x4x0.5/27 = 2.22 yd³
7. Concrete yardage - quick estimate
To calculate concrete yards for a slab, footing or wall, measure the length, width and depth in feet, or let the calculator above do the math and give you exact cubic yards without guessing. The formula is length x width x depth in feet, divided by 27. Example: a slab 20 ft long and 15 ft wide at 6 inches (0.5 ft) deep is 20 times 15 times 0.5, which equals 150 cu ft; divided by 27 that is 5.56 cubic yards. Add 10 percent waste and order 6.12 yd³.
Formula: CY = L x W x D / 27 | Example: 20x15x0.5/27 = 5.56 yd³
8. Calculating concrete cost for invoice
To stay on budget, know how to calculate the cost of concrete. Concrete is made from cement, aggregate (gravel and sand) and water; buy the raw materials separately or order ready mix. First calculate the cubic yards you need with the calculator, then multiply by the price per yard. If you are mixing yourself, price each component: cement bags, sand, gravel, water and any additives. Do not forget delivery fees, labor, prep and finishing. That gives the full cost, not just the concrete but the concrete placed and finished. The steps: calculate the volume in cubic yards, multiply by the cost per yard for ready mix or sum the materials if mixing on site, add delivery charges, then include labor, prep and finishing. Example: 5 cubic yards of ready mix at $120 per yard plus $75 delivery is 5 times 120, which equals $600, plus $75, for a $675 total cost. Example mixing on site: 1 cu yd takes cement at $150, sand $50, gravel $40 and water with additives $10, for $250 in materials only; add labor and equipment for the final estimate to invoice.
9. Concrete price for contractors - how to price and invoice
Contractor pricing combines material, labor, equipment, overhead, profit margin. Estimate volume multiply by material cost then add labor and other expenses. This ensures profitable yet competitive price. Example material 4 yards times $100 per yard equals $400 labor 3 hours times $50 per hour equals $150 equipment $50 total before profit equals $600 profit 20 percent equals $120 final price $720 to invoice. Add markup for profit using our profit margin calculator. Part of InvoiceTools so you can calculate cost then create invoice with markup.
10. Concrete mix ratio - cement sand gravel water
To mix concrete you need the right amounts of cement, sand, gravel and water, scaled by volume for strength and durability. A typical mix ratio is 1 part cement, 2 parts sand, 3 parts gravel and 0.5 part water by weight, plus additives if needed. For 1 cubic yard, that is about 6 bags of cement at 94lb each, 0.5 cu yd of sand, 0.75 cu yd of gravel and 30 gallons of water. Adjust for strength: 3000 psi uses 1:2:3, 4000 psi uses 1:1.5:2.5. Use the mix calculator to figure the bags and materials, then invoice with the material list.
Which concrete shape fits your pour?
1. Slab - most common for invoices
A rectangular slab is length times width times thickness. 4 inches is typical for a patio or driveway, 6 inches for heavy loads. A 10 by 10 slab at 4 inches is 33.33 cubic feet, or 1.23 cubic yards, 1.36 with waste. Use it for driveway, patio, sidewalk and floor invoices.
2. Footing - foundation invoices
A footing is length times width times depth. 12 inches wide by 12 inches deep is typical for residential work. Example: 20ft long at 12 inches wide and 12 inches deep equals 20 cu ft, or 0.74 cu yd. Use it for deck footing, wall footing and foundation invoices.
3. Column, round, curb, stairs - specialty
A column is pi times the radius squared times the height. A curb or gutter is a long, narrow shape: length times the average cross section. Stairs are steps times rise, run and width. Example: a column 12 inches in diameter and 4ft tall is 3.14 cu ft, or 0.12 cu yd. Use these for specialty concrete invoices.
Quick cubic yard, bag and cost calculators
These 4 small calculators are shortcuts from the full calculator above. Each one answers one simple question: enter your numbers and see an instant answer in plain words. Each links to the full calculator for the complete invoice breakdown.
Slab size → concrete volume
Enter your slab dimensions. We convert thickness from inches to feet and calculate cubic feet and cubic yards. Use this when you know length, width, thickness.
Length
Width
Thickness
Formula: (Length × Width × Thickness/12) = Cubic Feet, ÷27 = Cubic Yards
Result: 33.33 cu ft = 1.23 yd³
Example: 10 ft × 10 ft × 4 in thick = 33.33 cubic feet = 1.23 cubic yards of concrete needed.
Cubic yards → bags needed
Already know cubic yards from above? Enter it and choose bag size. We tell you how many bags to buy. 80lb bag = 0.6 cu ft, 60lb = 0.45, 40lb = 0.33.
Total Concrete
Bag Size
Formula: (Cubic Yards × 27) ÷ Bag cu ft = Number of bags
You need: 56 bags of 80lb bags
Example: 1.23 yd³ = 33.21 cu ft ÷ 0.6 = 56 bags (we round up).
Cubic feet → cubic yards
If you have cubic feet from a measurement, convert it to cubic yards. Concrete is sold by cubic yard, so this is needed for ordering.
Cubic Feet You Measured
Formula: Cubic Feet ÷ 27 = Cubic Yards
Result: 1.23 yd³
Example: 33.33 cu ft ÷ 27 = 1.23 cubic yards.
Cost → total to invoice
Know your concrete volume? Add price per yard and labor. We calculate concrete cost, total cost, and what to charge on invoice.
Volume (with waste)
Includes 10% waste
Price per Yard
Ready-mix $120-$200
Labor Cost
Flat or per sq ft
Formula: Concrete Cost = Volume × Price per Yard, Total = Concrete Cost + Labor
Concrete cost: $204 | Total to invoice: $404
Example: 1.36 yd³ × $150 = $204 concrete + $200 labor = $404 total to put on invoice.
Concrete Volume Comparison Table - Live Examples
How different shapes convert to cubic yards
| Shape | Formula | Example Input | Result Cubic Yards |
|---|---|---|---|
| Slab 10×10×4in | L×W×H/12 ÷27 | 10×10×0.33 ft | 1.23 yd³ |
| Footing 20ft long | L×W×D ÷27 | 20×1×1 ft | 0.74 yd³ |
| Column 12in dia 4ft | π×r²×H ÷27 | r0.5ft H4ft | 0.12 yd³ |
| Curb 100ft | L×W×D ÷27 | 100×1.5×0.5 ft | 2.78 yd³ |
All values include exact volume. Add 10% waste for ordering. Full calculator above adds waste automatically.
How to work out how much concrete you need in five steps
Enter length width thickness
Measure the length and width in feet and the thickness in inches; a 4 inch slab is typical, 6 inches for heavy loads. The calculator converts thickness from inches to feet by dividing by 12. Example: a 10x10 slab at 4 inches is 0.33 ft thick.
Choose shape and waste
Choose slab, footing, column, stairs or curb and gutter. Enter a waste percent; 10 percent is standard for spillage and an uneven base. Example: 1.23 yd³ plus 10 percent equals 1.36 yd³ to order.
Enter price and bag size
Enter price per cubic yard $150 typical ready mix $120 to $200, bag yields of 0.6, 0.45 and 0.33 cubic feet for 80lb, 60lb and 40lb for bags needed calculation. Example 80lb bag 0.6 cu ft 62 bags for 1.36 yd³.
Enter labor to invoice
Enter labor rate per sq ft $2 to $8 or flat. The concrete is priced on the yardage with waste, labour on area or a flat figure, and the two together are what you invoice. Add markup for profit 20 percent.
Copy invoice line and create invoice
Copy the results or the invoice line-item template. Example: Concrete slab, 10x10 at 4 inches thick, 1.36 yd³ with 10 percent waste, 62 bags, at $150 per yd³, $404 total. Paste it into the InvoiceTools invoice generator to create a professional invoice with the client name, date and terms.
Sample invoice clause for concrete
Concrete estimate based on [length]x[width] [thickness] inch thick [shape] [waste] percent waste [bags] bags [price] per cubic yard labor [labor]. Total [total] plus tax if applicable delivery fee [delivery] plus. 50 percent deposit required before pour. Includes prep, pour, finish, cleanup.
Concrete examples: slab, footing, column, curb and stairs
10x10 slab example - Standard invoice
A slab 10x10 at 4 inches thick, with 10 percent waste, 80lb bags and $150 per yard: 33.33 cu ft, 1.23 cu yd exact, 1.36 with waste, 62 bags, $204 of concrete, plus labor at 100 sq ft times $2 for $200, comes to $404 to invoice. This is the most common patio and sidewalk invoice.
Footing example - Foundation invoice
A footing 20ft long, 12 inches wide and 12 inches deep, with 10 percent waste at $150 per yard: 20 cu ft, 0.74 cu yd exact, 0.81 with waste, 37 bags, $122 of concrete plus $100 labor, comes to $222 to invoice for a deck footing.
Round footing column example
A round footing with a 1.5 ft radius and 2 ft depth, with 10 percent waste: 14.13 cu ft, 0.52 cu yd, 0.57 with waste, 26 bags, $86 of concrete plus $50 labor, comes to $136 to invoice for a pier footing.
Curb and gutter example - 100 ft
A curb 100 ft long, 1.5 ft wide and 0.5 ft deep, with 10 percent waste at $150 per yard: 75 cu ft, 2.78 cu yd exact, 3.06 with waste, 138 bags, $459 of concrete plus $300 labor, comes to $759 to invoice for a curb and gutter job.
How is concrete volume calculated? The formula explained
Slab and wall formula
Cubic yards equal length times width times thickness, all in feet, divided by 27. Divide thickness in inches by 12 to get feet. Example: a 15x10 slab at 0.5 ft thick is 15x10x0.5, which equals 75 cu ft; divided by 27 that is 2.78 cu yd.
Circular slab formula
Round shapes use the radius, which is half the diameter. Example radius 6 ft depth 0.5 ft 3.14x36x0.5 equals 56.52 cu ft divided by 27 equals 2.09 cu yd.
Yardage and waste formula
Yardage with waste equals the exact cubic yards times 1 plus the waste percent divided by 100. Example: 1.23 yd³ plus 10 percent waste equals 1.36 yd³. Always add 10 percent for spillage and an uneven base.
Bags and cost formula
Bags needed equal the cubic feet with waste divided by the cubic feet per bag: an 80lb bag is 0.6 cu ft, a 60lb bag 0.45 cu ft. Concrete cost equals the cubic yards with waste times the price per yard. The total to invoice is the concrete cost plus labor plus your profit markup.
Concrete formula and methodology
Volume is length × width × thickness, all in feet, divided by 27 to reach cubic yards; thickness in inches is divided by 12 first. Circular pours use π × radius² × depth, footings and curbs use the rectangular formula along their run, and stairs are the number of steps × rise × run × width. Waste multiplies the result by one plus your percentage. Bags are the cubic feet with waste divided by the yield of the bag: 0.6 for 80lb, 0.45 for 60lb, 0.33 for 40lb. Cost is yards with waste × your yard price, plus labour at your rate, plus whatever margin you price the job at. Nothing is stored and no data leaves your browser. Figures are estimates for planning and quoting; confirm the order with your supplier.
Concrete questions, answered
Common questions about concrete quantity, bags, cost, price to invoice concrete jobs.
How much concrete do I need for 10x10 slab 4 inch?
A 10 by 10 foot slab at 4 inches needs 1.23 cubic yards, or 1.36 with the usual 10 percent waste. That is a short ready-mix load or about 62 80lb bags, and bags at that volume mean mixing for most of a day, so it is the point where most people order the truck instead.
How to calculate concrete for circular slab?
Measure the radius rather than the diameter, since the radius is what the formula squares, and measure the hole after digging rather than before. A 6 foot radius pad 6 inches deep comes to 2.09 cubic yards, and getting the radius wrong by six inches moves that by nearly a fifth.
How many 80lb bags of concrete in a cubic yard?
45. A cubic yard is 27 cubic feet and an 80lb bag yields about 0.6 of a cubic foot. In 60lb bags it is 60, and in 40lb bags 90, which is why bag size matters more to your back than to your budget.
How to calculate concrete cost to invoice client?
The concrete itself is rarely half the bill. Add delivery and any short-load fee, then the excavation, base, forms, reinforcement, labour and finish, and price the job on the total. The invoice line above is filled in from your figures, ready to paste into a quote or an invoice.
What is concrete mix ratio?
For mixing on site, 1 part cement to 2 parts sand and 3 parts gravel is the common starting point, with water around half the weight of the cement. Beyond roughly a cubic yard, matching that ratio consistently by hand is harder than it sounds, which is an argument for ready-mix.
Do I need to add waste factor?
Yes. Subgrade is never perfectly level, forms bow slightly, and some concrete stays in the barrow or the drum. Ten percent covers a straightforward pour and 15 suits complex shapes. Running out mid-pour leaves a cold joint, which costs far more than the extra you ordered.
How many cubic yards of concrete do I need?
Multiply length by width by thickness in feet, then divide by 27. A 4 inch slab is 0.33 feet thick, a 6 inch slab is 0.5. Add 10 percent on top before you order, because the ground is never as flat as the drawing.
How much does a yard of concrete cost?
Ready-mix typically runs $120 to $200 a cubic yard delivered, and the spread is regional. Ask for the delivery charge and the short-load fee in the same call, because on a small pour those can cost more than the concrete.
What is a short-load fee?
A charge for ordering less than the supplier's minimum, usually around four or five yards. If your figure lands just under a threshold it is often cheaper to order the next size up than to pay the fee.
How thick should a concrete slab be?
Four inches for patios, paths and shed bases. Driveways want 4 to 6 inches, and 6 with a stronger mix if anything heavier than a car parks on it. Thickness changes volume proportionally, so 4 to 6 inches adds half again to the order.
How many bags of concrete equal a cubic yard?
45 at 80lb, 60 at 60lb, or 90 at 40lb. Above about one cubic yard, mixing by hand costs more in time than delivery saves and the mix is harder to keep consistent.
How long does concrete take to cure?
Firm enough to walk on after 24 to 48 hours, ready for vehicles after about a week, and at full strength around 28 days, which is the age strength is quoted at.
What concrete strength do I need?
3,000 to 3,500 PSI covers slabs, paths and footings. Go to 4,000 PSI or above for driveways in freeze and thaw climates, or anywhere vehicles will stand.
How do I price a concrete job for a client?
Take the yardage here, add delivery and any short-load fee, then excavation, base, forms, reinforcement, labour and finish. Concrete is rarely half the finished cost, so pricing off the yard price alone is how a job earns nothing.
Can I pour concrete in cold or wet weather?
Below about 40F it cures slowly and needs blankets or an accelerator; below freezing it can be damaged outright. Heavy rain on fresh concrete weakens the surface. Neither changes the volume you need, only the day you book.
Do I need rebar or mesh?
Most slabs use mesh or rebar to control cracking, and anything carrying vehicles should have it. It is priced by area rather than volume, so quote it as its own line.
How much concrete do I need for a fence post?
A hole three times the post width and a third of the post length is the usual rule. A 4 inch post in a 12 inch hole, 2 feet deep, takes about 1.6 cubic feet, so two 80lb bags per post is a safe buy.
Is the concrete calculator free and private?
Yes. No signup, no uploads, and every figure is worked out in your browser and gone when you close the tab.
What should a concrete quote include?
The pour itself in cubic yards, then prep, forms, reinforcement, labour and the finish as separate lines, plus access notes and what happens if the ground is worse than expected. A quote that shows only a yard price invites an argument about everything else.
Should I charge the client for wasted concrete?
Price it in rather than adding it later. Surplus cannot be returned once batched, so the 10 percent allowance is a genuine cost of doing the job properly and belongs in the quoted price.
When should I invoice a concrete job?
The day the pour is finished. The work is visibly complete, which is the moment a client is least likely to dispute it, and every day you wait is a day you are financing them.
How do I quote for difficult access?
As its own line, priced before you commit. A pump or a long barrow run can cost more than the concrete on a small job, and it is a decision made when the truck is booked rather than a surprise on the invoice.