Construction

Paint Calculator

Estimate gallons of paint for walls, including multiple coats.

Surface area

Number of coats

Coverage per gallon (ft²/gal)

Price per gallon ($)

Calculated Output

Paint needed (gal) 3

Total cost ($) 0

Formula: gallons = area × coats ÷ coverage

Step-by-Step Breakdown

1. Values used:

2. Surface area = 400

3. Number of coats = 2

4. Coverage per gallon = 350 ft²/gal

5. Price per gallon = 0 $

7. Paint needed = 3gal

8. Total cost = 0$

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The math behind it

Gallons = total area × number of coats ÷ coverage per gallon, rounded up.

One gallon typically covers ~350 ft² per coat on smooth, primed surfaces (less on rough/porous ones).

400 ft² with 2 coats at 350 ft²/gal → 800 ÷ 350 = 2.3 → 3 gallons.

Do I count doors and windows?

Subtract large openings; for small rooms it's safer to leave them in as extra allowance.