How to use the Mural Paint Coverage Calculator
- Measure each wall. Enter width × height for every surface you’ll paint, one row per wall. Use + Add wall for more, and switch to Meters & liters if your tape and paint are metric.
- Skip the openings. Add a row for each door and window with + Door or + Window, then adjust the size and the count. Leave out a window if you plan to paint over its frame.
- Describe the job. Set the number of coats, the coverage printed on your can, the Surface you’re painting on, and a waste allowance. Tick Primer coat if the wall will be primed first.
- Split the area by color. Under Mural colors, give each paint a share of the wall. Whatever you don’t assign becomes the base color. Each row shows how much of that color you need and the cheapest cans to buy.
- Shop with the list. Copy shopping list or Download CSV gives you every color, the primer, the can sizes and the estimated cost. Open Can sizes & prices to enter the prices at your store.
Why mural estimates go wrong
House-paint calculators assume one color on a smooth wall. A mural is different in three ways, and each one can leave you short on the second day of painting.
First, coverage on the can is a best case. US labels usually promise 350 to 400 square feet per gallon, which is 8.6 to 9.8 m² per liter. UK and European tins often quote 10 to 12 m² per liter. Those figures assume a smooth, sealed surface, a roller and a steady hand. Exterior walls are rarely any of those.
Second, the surface eats paint. Bare drywall and fresh plaster soak up the first coat. Stucco and brick have far more surface than their flat measurements suggest, and every coat has to fill the texture. The calculator adds a planning allowance for each surface: 20% on the first coat for bare drywall, 10% on every coat for light texture, and up to 35% on every coat plus 20% on the first for brick or block. Over two unprimed coats, that works out to 10% more paint for drywall, about 34% more for heavy stucco and about 49% more for brick. If you prime, the first-coat surcharge lands on the cheaper primer instead.
Third, you buy each color separately. A wall that needs 2.13 gallons in total doesn’t need two gallon cans and a quart. Split across six colors, it needs six containers, and the small ones dominate the bill.
Working through one wall
Take two walls, 24 × 10 feet and 12 × 10 feet, with one 3 × 7 foot door: 360 − 21 = 339 square feet to paint.
- Topcoats: 339 × 2 coats ÷ 350 sq ft per gallon = 1.94 gallons, plus 10% waste = 2.13 gallons (8.1 liters).
- Primer on bare drywall: 339 × 1.2 for the thirsty first coat ÷ 300 sq ft per gallon = 1.36 gallons, plus 10% = 1.49 gallons.
- One accent color at 5% of the wall: 2.13 × 0.05 = 0.11 gallons. A quart covers about 87 square feet per coat at that rate, so one quart is plenty.
Skip the primer on the same drywall and the topcoats go up to 2.34 gallons, because the first coat now does the soaking.
How far one can goes
At the default coverage of 350 sq ft per gallon or 10 m² per liter, before waste:
| Can | One coat | Two coats |
|---|---|---|
| Quart (0.95 L) | 87.5 sq ft | 43.75 sq ft |
| Gallon (3.79 L) | 350 sq ft | 175 sq ft |
| 5 gallons (18.9 L) | 1,750 sq ft | 875 sq ft |
| 0.75 L tin | 7.5 m² | 3.75 m² |
| 2.5 L tin | 25 m² | 12.5 m² |
| 5 L tin | 50 m² | 25 m² |
A quick sanity check for any mural: two coats on a smooth wall use about one gallon per 175 square feet, or one liter per 5 m². If your estimate is far off that, look at the surface setting and the openings first.
Tips from practice
Box your base color. If the background takes several cans, pour them all into one clean bucket and mix before you start. Separate cans can differ slightly in tint, and the seam shows in raking light.
Buy small colors in the smallest can, not the cheapest per gallon. A gallon of a 3% accent is mostly leftover paint that will skin over in the garage. The calculator’s shopping list already favors quarts or 0.75 L tins when they cover the need.
Keep a labeled touch-up jar for every color. Write the color name, mix recipe and wall on a strip of tape. Outdoor murals get scuffed and tagged, and matching a custom mix from memory a year later rarely works.
Check the temperature on the label. Many latex paints want 50°F (10°C) or warmer for application and for the night after. A cold evening can leave the paint chalky and the coverage thin, which costs you a coat.
Price the job with the paint in it. Materials are a real line on a mural quote. Carry this total into the Commission Price Calculator, and if you’re quoting by the hour, set your rate with the Freelance Hourly Rate Calculator.