Multi-Coat Paint Coverage Calculator
Most paint jobs need more than one coat for full, even color, which multiplies the paint you must buy. This calculator takes the surface area, the manufacturer's coverage rate per gallon, the number of coats, and a waste allowance, then returns the total gallons and the number of standard cans to purchase. It also subtracts door and window openings if you enter them.
Multi-coat paint formula
Net area = total area - openings
Total area across coats = net area * coats
Gallons (raw) = total area / coverage per gallon
Gallons with waste = gallons * (1 + waste / 100)
Cans = ceiling( gallons with waste / can size )
Coverage per gallon is set by the paint maker, commonly around 350 to 400 square feet per gallon for one coat on a smooth, sealed surface. Porous, textured, or dark-to-light surfaces cover less per gallon and may need more coats.
Worked example
An 800 square foot room with 60 square feet of openings has 740 square feet of paintable wall. Two coats cover 1,480 square feet. At 350 square feet per gallon that is 4.23 gallons; adding 10 percent waste gives 4.65 gallons. Rounded up to 1 gallon cans, you buy 5 cans.
Paint estimating notes
- Typical interior latex coverage is about 350 to 400 square feet per gallon per coat on smooth, primed walls.
- Bare drywall, rough plaster, and textured surfaces absorb more and cover less per gallon.
- Big color changes (dark to light, or vivid colors) often need a primer plus two finish coats.
- Always add a waste allowance and round up to whole cans; a little extra is useful for touch-ups.
- Check the specific product label for its stated coverage rate.
Multi-Coat Paint Coverage Calculator: frequently asked questions
How many gallons of paint do I need for two coats?
Multiply the net paintable area by the number of coats, then divide by the coverage per gallon. For 740 square feet at two coats and 350 square feet per gallon, that is about 4.23 gallons before waste, or roughly 5 one-gallon cans after a 10 percent allowance.
How much area does a gallon of paint cover?
Most interior latex paints cover about 350 to 400 square feet per gallon for one coat on a smooth, sealed surface. Textured or unprimed surfaces cover less. Always check the product label, which this calculator uses as an editable input.
Should I subtract doors and windows?
For a more accurate estimate, yes, subtract large openings like doors and windows from the total wall area. For small jobs many painters skip this and let the extra serve as a buffer. This calculator lets you enter openings to subtract.
Why do I need more than one coat?
A single coat often leaves uneven color and lets the previous surface show through, especially over a different color or on porous surfaces. Two coats give full, uniform coverage and durability, which is why most jobs are calculated for two coats.
Sources and methodology
- Coverage per gallon is a manufacturer-specified, user-editable input; the gallons calculation is straightforward area arithmetic.
- U.S. Environmental Protection Agency: Safer Choice (lower-VOC paint guidance).
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.