Paint Calculator
Know how much paint to buy before you open a tin.
Paintable area, gallons and cost for walls, ceilings, trim, doors and exteriors, with coats, primer, surface porosity and openings taken off, plus a line you can put straight on a quote.
- Free, no signup
- Runs in your browser
- Doors and windows deducted
- Primer and coats
Enter room details
Surface
Length (ft)
Width (ft)
Height (ft)
Doors (21 sq ft each)
Windows (15 sq ft each)
Coats
Coverage (sq ft per gallon)
Price per gallon ($)
Labor rate ($ per sq ft)
3D preview · drag to rotate 0°
Whole roomInclude ceiling?
Quick examples for invoices
Your paint estimate to invoice
$400.00
Total to invoice - $100 paint + $300 labor
Formula text
Invoice line item template for painting
Line item
Watch the calculator fill itself in
The same panel you used above, working out a 12 by 12 room, then the trim, then an exterior. The fields change with the surface, and so does the drawing.
Your paint order
0 gal
Gallons to buy
yd³ = L × W × T ÷ 27
If the surface is rough
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 coverage to an invoice that gets paid
Working out how much paint you need is the easy part. These are the four places the money goes missing between measuring the walls and being paid for the job.
Quote the work, not the paint
Paint is rarely a quarter of the finished cost. Preparation is the job: filling, sanding, caulking, masking, two coats and the making good afterwards. A client who was quoted a price per tin will argue about every hour of it later.
Itemise it once on a written quote and the conversation is over before it starts.
The second coat is not a rounding error
Coverage figures on a tin assume a sealed, even surface in good light. New plaster, a colour change or a porous exterior wall will drink the first coat, and the ten percent you add for touching in is real money across a whole house.
Paint coverage is the number everything else hangs on. Wall paint typically covers less than the tin claims once the surface is porous, and ceiling paint less again because you are cutting in around edges and working overhead. Measure the area, decide the number of coats, then price the labour separately.
The profit margin calculator checks the job still pays once that is counted.
Access and height change the price
Scaffold, a tower, cutting in around a stairwell or working around furniture that has to be moved and put back can cost more than the paint on a small job. They are decisions made before the brush is opened, so they belong on the quote rather than in a conversation halfway through the week.
Invoice while the smell is still in the air
Decorating is one of the few trades where the work is unmistakably finished: the client can see it. Send the invoice the day you clear the dust sheets, while they are still pleased with it, and add late fee terms so a slow payer has a reason to be quick.
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 paint calculator instead of guessing tins?
Calculating paint in Excel misses doors windows waste and coats. Our calculator prevents short buying and helps you invoice accurately with gallons, cost, labor, total. Part of InvoiceTools suite so you can calculate then create invoice directly.
Accurate gallons for invoice
Wall area is 2*(L+W)*H, minus 21 sq ft per door and 15 per window. Example: a 12x12 room with 8ft walls has 384 sq ft of wall; minus 36 that leaves 348 paintable, 0.99 gal exact, 1 gal to buy.
From estimate to invoice in one click
See paint cost gallons times price, labor cost sq ft times rate, total to invoice. Copy invoice line template auto generated.
Unique - Waste, ceiling, labor included
Include ceiling or walls only, 1 2 3 coats, coverage 300-400, labor rate $0.50 to $2, price per gallon $30 to $80.
Built for painting contractors who invoice
Mobile first works on job site, client side only, no data stored. For interior, exterior, residential, commercial.
How much does a gallon of paint cover?
1. Interior latex - most common
350 sq ft per gallon per coat is typical; the range is 300 to 400. Example: a 400 sq ft living room at 350 coverage needs 1.14 gallons for 1 coat, so buy 2 gallons.
2. Primer - lower coverage
200 to 300 sq ft per gallon. New drywall, or going from dark to light, needs primer. Example: 400 sq ft of new drywall with primer at 250 is 1.6 gallons, so buy 2.
3. Exterior - weather and texture
250 to 350 sq ft per gallon; rough stucco runs lower. Example: 1000 sq ft of exterior at 300 is 3.33 gallons, so buy 4 gallons. Add 10 percent waste.
Quick area, gallons and cost calculators
These 4 shortcuts come from the full calculator above. Each answers one question in plain words: enter your numbers and see an instant answer.
One wall → paint needed
Enter wall length and height. We calculate area and gallons for 1 coat at 350 sq ft per gallon.
Wall Length
Wall Height
Formula: Area = Length × Height, Gallons = Area ÷ 350
Area: 96 sq ft | Paint: 0.27 gal
Example: 12 ft × 8 ft = 96 sq ft = 0.27 gallons (buy 1 gallon).
Room size → paint needed
Enter room length, width, height. We calculate total wall area for 4 walls and gallons for 1 and 2 coats.
Length
Width
Height
Formula: Wall area = 2×(Length+Width)×Height
Walls: 384 sq ft | 1 coat: 1.10 gal | 2 coats: 2.19 gal
Example: 12×12 room 8 ft = 384 sq ft walls = 1.10 gal for 1 coat, 2.19 gal for 2 coats.
Area → gallons to buy
If you know the total sq ft to paint, enter the coverage per gallon (350 is standard) and the coats. We give the exact gallons and the rounded-up amount to buy.
Total Area
Coverage
Coats
Formula: Gallons = Area ÷ Coverage × Coats, Buy = Round up
Exact: 1.14 gal | To buy: 2 gal
Example: 400 sq ft ÷ 350 × 1 coat = 1.14 gal, buy 2 gallons.
Paint cost → total invoice
Enter gallons you will buy, price per gallon, and labor. We calculate paint cost and total to invoice client.
Gallons to Buy
Price per Gallon
Labor
Formula: Paint Cost = Gallons × Price, Total = Paint Cost + Labor
Paint: $100 | Total to invoice: $400
Example: 2 gal × $50 = $100 paint + $300 labor = $400 total to invoice.
How to work out how much paint you need in five steps
Enter room length width height
Measure the room length and width in feet and the height; 8 ft is standard, 9 ft for tall rooms. Example: a 12x12 room at 8 ft has 384 sq ft of wall area. For a single wall, use wall-only mode.
Enter doors and windows
Count the doors and windows in the room. Each door takes 21 sq ft and each window 15 sq ft off the wall area. Example: 1 door and 1 window subtract 36 sq ft, leaving 348 sq ft paintable for a more accurate gallon count.
Choose coats and coverage
Choose 1, 2 or 3 coats; 2 is standard. Coverage per gallon: 350 for interior latex, 250 for primer, 300 for exterior. Exact gallons equal the paintable area divided by coverage, times coats, rounded up to buy.
Enter price and labor to invoice
Enter the price per gallon ($50 is typical) and a labor rate per sq ft ($0.75) or a flat fee ($300). Paint cost is gallons to buy times price; labor is area times rate, or the flat fee. The total to invoice is paint plus labor, plus a markup of 15 to 30 percent for profit.
Copy invoice line and create invoice
Copy the results or the invoice line-item template. Example: Painting a 12x12 room, 348 sq ft of wall, 1 coat, 1 gallon at $50 plus labor, $311 total. Paste it into the InvoiceTools invoice generator to create a professional invoice with the client name, date, terms and late fee.
Paint formula and methodology
Surface area equals the walls, plus the ceiling if painted, minus windows and doors. Wall area is 2 times length plus width, times height. A 12 by 12 room with 8 foot walls leaves 348 square feet once a door and two windows come off. Exact gallons equal the paintable area divided by the coverage per gallon, times the number of coats. Typical coverage is 350 sq ft per gallon for interior latex, 200 to 300 for primer, 250 to 350 for exterior. Gallons to buy are the exact gallons rounded up. Paint cost equals gallons to buy times price per gallon. Labor equals the paintable area times a rate per sq ft, or a crew at 150 to 200 sq ft per hour times the hourly rate. The subtotal is paint plus labor plus prep, primer, trim materials and overhead. The total to invoice is the subtotal times 1 plus a profit margin of 15 to 30 percent, plus a 5 to 10 percent contingency. Nothing is stored and there is no API: the calculations run in your browser. Estimates are for informational purposes; verify against local rates before invoicing.
Using this as a house painting cost calculator
The gallons are half the answer. To turn coverage into a price, take the paint and primer this page works out, multiply by what you actually pay per gallon, then add the sundries: masking, filler, rollers and the dust sheets. Labour is the hours the job takes at your own rate, and preparation is usually longer than the painting. Add access and disposal, allow about ten percent waste on materials, and you have the cost of the job rather than the cost of the paint. To put markup and overhead on top of that and produce a document you can send, use the cost estimator.
Painting questions, answered
Common questions about paint needed, coverage, cost to invoice painting jobs.
How much paint do I need for 12x12 room?
Walls and ceiling on a 12 by 12 room with 9 foot ceilings come to about 540 square feet before openings, so two coats at 350 square feet a gallon is roughly 3 gallons. Take off a door and two windows and you are closer to 2.7, which still means buying 3.
What is fair price to charge for painting?
Interior work commonly runs $2 to $4 a square foot and exterior $1.50 to $3.50, with hourly rates of $25 to $45 a painter. Where you sit in that range depends on prep more than paint: filling, sanding and masking are the hours that decide whether the job pays.
How much should it cost to paint 1000 sq ft house?
At typical interior rates, somewhere between $2,000 and $4,000, and the spread is prep and ceiling height rather than paint quality. Price the area here, then add the prep hours honestly, because that is where painting jobs lose money.
How do painters estimate a job?
Measure the surfaces, take off the openings, decide coats and primer, then price paint and labour separately. The part most estimates miss is condition: bare drywall, rough render and chalky exteriors all drink far more paint than a wall that was painted three years ago.
How do I improve painting business profit margins?
Two levers, and neither is buying cheaper paint. Cut the time lost to prep you did not quote for by writing surface condition into the quote, and stop absorbing extra coats that were never agreed. A wall that needs three coats should be quoted as three.
How much paint do I need per square foot?
One gallon covers roughly 350 square feet in one coat on a previously painted, smooth wall. Two coats halve that to about 175 square feet a gallon, which is the figure to plan with, because one coat rarely looks finished over a colour change.
How many gallons of paint for a 12x12 room?
Walls and ceiling come to about 526 square feet after a door and two windows come off, so two coats need roughly 3 gallons. Walls only is closer to 2.
How much paint do I need for the exterior of a house?
Measure the perimeter, multiply by the wall height and add the gables, then take off doors and windows. A 120 foot perimeter at 10 feet with 80 square feet of gable is about 1,120 square feet, which is 6 to 7 gallons at two coats.
Do I need primer?
Yes on bare drywall, new timber, patched repairs and any large colour change, especially light over dark. Primer covers slightly further than topcoat, so treat it as its own coat rather than adding one to the count.
How much more paint does textured or bare surface take?
Light texture adds roughly 10 percent, heavy texture or render 25, and bare drywall or timber up to 35. It is the single most common reason a job runs short mid-wall.
How do I calculate paint for trim and skirting?
By the run, not the room. Multiply the linear feet by the board width in feet, then by the number of faces you are painting. Sixty feet of 5 inch skirting painted on two faces is about 50 square feet, which is well inside a single gallon.
How many coats of paint do I need?
Two on most walls. One is enough only when you are refreshing the same colour on a sound surface, and three is realistic for strong colours, or light over dark, whatever the tin claims.
How much should I charge to paint a room?
Work from the area rather than a room size, because a 12 by 12 room with 12 foot ceilings is a third more wall than one with 9 foot ceilings. Price the surface here, add your prep hours, and check the result against what you would want for the day.
Should I deduct doors and windows?
Yes, at about 20 square feet a door and 15 a window. On a small room that is over 10 percent of the wall area, which is a gallon on a large job.
How do I estimate paint for a ceiling?
Length times width, and nothing else. Ceilings often need an extra coat because they are viewed in raking light, so plan two even when the walls need one.
How much does a gallon of paint cost?
Trade emulsion is typically $25 to $45 a gallon, and premium or specialist finishes considerably more. On most jobs paint is a fifth or less of the total, so buying cheap paint to save money usually costs more in extra coats.
Is the paint calculator free and private?
Yes. No signup, nothing uploaded, and every figure is worked out in your browser and gone when you close the tab.
What should a painting quote include?
The surfaces by name, the number of coats, whether primer is included, and what preparation is covered. Most disputes on painting jobs are about prep nobody wrote down, not about paint.
Should I quote painting by the square foot or by the day?
Square foot pricing is easier for a client to compare and easier for you to check afterwards. Day rates hide the prep, which is exactly where painting jobs lose money.
How do I charge for extra coats?
State the number of coats on the quote and price additional coats as a separate line. A wall that needs three coats because of a colour change is a bigger job, and it should be a bigger number.
Should paint be a separate line on the invoice?
It usually helps. It shows the client what the materials cost, keeps your labour rate from looking inflated, and makes it obvious why a premium finish costs more.
How do you calculate house painting cost?
Cost is materials plus labour plus the parts people forget. Work out the gallons from the wall area and the number of coats, multiply by what your paint actually costs, then add primer, masking, filler and rollers. Labour is the hours the job takes at your rate, and preparation is usually longer than the painting itself. Add disposal and access, and allow about ten percent waste on materials.
How much paint do I need for a whole house?
Measure each room and add them together rather than working from the floor area, because ceiling height and the number of windows change the answer more than square footage does. One gallon covers roughly 350 square feet per coat, so a room with 1,000 square feet of wall takes about three gallons for one coat and six for two.