Calculators
Paint Calculator
Enter your walls, subtract doors and windows, add the ceiling and primer if you need them, and see exactly which cans to buy, in gallons or liters for your country.
Units: feet, inches and US gallons. Cans: quart, gallon, 5-gallon pail.
Walls
A rectangular room is two pairs of equal walls — enter each pair once with “How many” set to 2.
Doors and windows (not painted)
Paint
Benjamin Moore lists 350–400 sq ft per gallon for its interior paints and 400–450 for Fresh Start primer; the lower figures are pre-filled. Use the spreading rate on your can if it differs.
Calculated on your device — nothing is sent anywhere. Real coverage depends on the surface, color change and application method.
Works in your browser. No account needed.
Frequently asked questions
How much paint do I need for a room?
Work out the wall area, subtract doors and windows, multiply by the number of coats and divide by the coverage. A 12 × 10 ft room with 8 ft walls has 352 sq ft of wall; minus one 36 × 80 in door (20 sq ft) and one 36 × 48 in window (12 sq ft) that is 320 sq ft. Two coats at 350 sq ft per gallon need about 1.83 gallons, so you buy two gallons.
How many square feet does a gallon of paint cover?
It depends on the product and the surface. Benjamin Moore lists 350–400 sq ft per gallon for Aura Bath & Spa interior paint and 400–450 sq ft for Fresh Start primer; the calculator starts from the lower figures. Rough, porous or unprimed surfaces absorb more, so always check the spreading rate printed on your own can and enter it.
How much does a liter of paint cover?
Manufacturers publish very different rates. Dulux UK quotes “up to” 13–14 m² per liter for its matt emulsions; Filli Boya (Türkiye) gives 13.5–19 m² per liter per coat for Momento Life; Asian Paints (India) quotes 250–270 sq ft per liter for the first coat of Tractor Emulsion and 130–150 for the second. The calculator pre-fills a figure for your country, and you can type the one on your tin.
Do I need primer?
Primer is usually recommended on new drywall or plaster, patched areas, bare wood, stained surfaces, and when making a big color change. Painting over a sound, similar color often needs no primer. Tick “Add primer” to include one coat over the walls and ceiling.
Why does the calculator suggest particular can sizes?
It picks the combination of the cans sold in your country that covers what you need with the least left over, while preferring fewer, larger cans — so three quarts become a gallon, and two 2.5 L tins become one 5 L tin. Can sizes follow major brands: quart, gallon and 5-gallon in the US; 2.5, 5 and 10 L tins from Dulux in the UK; 2.5, 7.5 and 15 L from Filli Boya in Türkiye; 1, 4, 10 and 20 L from Asian Paints in India.
Which countries are supported, and is anything uploaded?
The US, Canada, the UK, Australia, India, Germany and the EU, and Türkiye. The country is guessed from your browser language and can be changed; it only sets units, can sizes, the starting coverage and the currency symbol for prices you enter. Nothing leaves your browser.
About this tool
This paint calculator answers the question every painting job starts with: how many cans do I buy? Enter the walls as length × height (matching walls once, with a count), and it subtracts doors and windows using sizes you can edit — 36 × 80 in and 36 × 48 in are filled in for the US, 90 × 210 cm and 120 × 120 cm for metric countries. Add the ceiling if you are painting it, set the number of coats, and include primer if the surface needs it.
Coverage is the number that matters most, and it varies by product. The US preset starts at 350 sq ft per gallon, the lower end of the 350–400 sq ft Benjamin Moore lists for its Aura Bath & Spa interior paint, and 400 sq ft for primer (Fresh Start: 400–450). Metric presets use local manufacturers’ published figures where available — Dulux UK, Filli Boya in Türkiye, Asian Paints in India — and every value can be replaced with the spreading rate printed on your can.
Instead of a bare number of liters, the result is a shopping list in the cans actually sold in your country: quarts, gallons and 5-gallon pails in the US; 946 mL and 3.79 L cans in Canada; 2.5, 5 and 10 L tins in the UK and EU; 1, 2, 4, 10 and 15 L in Australia; 1, 4, 10 and 20 L in India; and 2.5, 7.5 and 15 L in Türkiye. Wall paint, ceiling paint and primer are listed separately, since they are usually different products, and optional prices give an estimated total.
Coverage rates are theoretical, and manufacturers say so: textured, porous or dark surfaces, a big color change, or spraying instead of rolling all use more paint. Keeping a little over for touch-ups is useful, and buying all the paint for a room from the same batch avoids slight color differences between cans.