Room size
Coats
Typical latex is about 350 sq ft per gallon, per coat. Check the can.
Buy
- Paintable sq ft
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- Gallons
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- Cans to buy
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- Est. cost
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Enter length, width, and height.
This is an estimate, not a spec and not a painting contractor quote. No labor, no painter, no product SKU. Coverage varies by product, color, sheen, and surface. Always check the number printed on the can. Quart pricing here is one-fourth of a gallon; store quarts often cost more per ounce.
How the paint is counted
This is wall math, not a brand product picker. Wall area is the room’s perimeter times height: 2 × (length + width) × height — not the floor plan. Each door knocks off 20 square feet (a typical 3 ft × 6 ft 8 in interior door). Each window knocks off 15 square feet. The ceiling, if you turn it on, is length × width. Openings cannot take the walls below zero.
Paintable area is that net square footage times coats (default 2). Gallons are paintable area ÷ coverage (default 350 sq ft/gal). We then round up to 1 gallon and 1 quart cans so a leftover still becomes another can.
wall_sq_ft = 2 × (L + W) × H net_walls = max(0, wall_sq_ft − doors×20 − windows×15) one_coat = net_walls + (ceiling ? L×W : 0) paintable = one_coat × coats exact_gal = paintable ÷ coverage cans = ceil(exact_gal × 4) quarts, then 4 qt = 1 gal
Example: 10 ft × 10 ft × 8 ft, 1 door, 1 window, 2 coats, 350 sq ft/gal, walls only. Walls 320 − 20 − 15 = 285 sq ft. Two coats = 570. 570 ÷ 350 = 1.63 gal → 1 gallon + 3 quarts (or 2 gallons).
FAQ
Why gallons from walls, not the floor plan?
A 10×10 floor is 100 square feet. Paint goes on the walls: 2 × (length + width) × height. The same room at 8 ft is 320 square feet of wall, not 100. Store-brand calculators often start from a product or a room type and hide that. This page starts from the four walls. The ceiling is optional (length × width) and is off by default.
How do coats change the gallons?
Paintable square feet = one-coat area × coats. Default is 2, the usual interior finish. One coat is a primer or a touch-up. Three shows up on a dark color change or a stained wall. Skip coats and you buy about half of what the second pass needs. Coats multiply the walls; they are not a labor line.
What does coverage in sq ft/gal mean — and why 350?
Coverage is how many square feet one gallon covers per coat, printed on the can. Default 350 for typical latex. Primer, dark colors, and rough drywall cover less — 250 to 300 is common. Type the number on the can you are buying. This field is not locked to a store-brand SKU.
Why subtract doors and windows?
You do not paint the opening. Each door knocks off 20 square feet (a typical 3 ft × 6 ft 8 in interior door). Each window knocks off 15. Fixture: 10×10×8 walls = 320; 1 door + 1 window → 285 net. Skip the deduction and you buy paint for holes. Openings cannot take the walls below zero.
How much paint for a 10×10 room?
Not 100 sq ft of floor. Walls at 8 ft = 320. Minus 1 door and 1 window = 285. Two coats = 570. At 350 sq ft/gal → about 1.63 gallons. Buy 1 gallon + 3 quarts, or 2 gallons. Height, openings, coats, and the can change it. That is can math, not a painting contractor quote.
Is this a painting contractor quote?
No. Quantity math only: walls, openings, coats, coverage, round up to cans. Not a painting contractor quote. No labor, no primer schedule, no surface prep, no painter finder, no product SKU. Confirm the can. Whoever rolls the wall has the last word.