Paint Calculator: Wall Area, Coats and Liters

Calculate your quantities

Enter your measurements below. Change the example allowance, product information and price to match your project.

Enter measurements and select Calculate.

Prices use your chosen currency. A zero price leaves cost at zero. Material estimates exclude labor, tax, delivery and accessories. Enter decimal feet, not feet-and-inches notation. Decimal point or comma accepted; omit thousands separators.

How to use this paint calculator

Covers the four walls of a rectangular room; ceiling and trim are excluded. Use product-specific coverage for your surface. The default coverage is illustrative. Cost uses whole US gallons, not fractional purchases.

Measure the relevant area or volume using the units shown beside each input.
Replace example product values with the supplier's yield, coverage, density or pack quantity where applicable.
Set the extra allowance explicitly. Enter zero when you want the geometric quantity without an allowance.
Select Calculate, then compare the unrounded purchasing basis with whole bags, boxes or packs where displayed.

Formula

Wall area = 2 × (length + width) × height − openings. US gallons = wall area × coats × (1 + extra / 100) / coverage. Liters = US gallons × 3.785411784.

Worked example

For a 10 × 10 ft room with 8 ft walls, subtract 40 ft² of openings from 320 ft²: net 280 ft². Two coats, 10% extra and 350 ft²/US gal yield 1.760 US gal = 6.662 L; round up to 2 one-gallon cans.

Six calculated examples

Only the first length changes in this table. All other inputs use the calculator's reset values shown above. These are mathematical scenarios, not measured supplier quotes.

paint quantity examples
First length	Calculated quantities
5 ft	Net wall area (ft²): 200; Paint (US gallons): 1.257; Paint (liters): 4.759; One-gallon cans: 2
8 ft	Net wall area (ft²): 248; Paint (US gallons): 1.559; Paint (liters): 5.901; One-gallon cans: 2
10 ft	Net wall area (ft²): 280; Paint (US gallons): 1.76; Paint (liters): 6.662; One-gallon cans: 2
12 ft	Net wall area (ft²): 312; Paint (US gallons): 1.961; Paint (liters): 7.424; One-gallon cans: 2
15 ft	Net wall area (ft²): 360; Paint (US gallons): 2.263; Paint (liters): 8.566; One-gallon cans: 3
20 ft	Net wall area (ft²): 440; Paint (US gallons): 2.766; Paint (liters): 10.469; One-gallon cans: 3

Frequently asked questions

Does it include the ceiling?

No. Calculate ceiling area separately and apply its product coverage and number of coats.

Are UK and US gallons identical?

No. This calculator uses US gallons. Use the liter result for metric purchasing.

Why use label coverage?

Surface texture, application method and the product affect coverage. A generic default is only an example.

Units and calculation limits

One foot is 0.3048 meters; one cubic yard is 27 cubic feet. Calculations retain precision until display; whole-package quantities are rounded up. Outputs estimate quantities from your measurements and assumptions. Confirm product coverage and units before ordering.