Paint Calculator for Two Coats
Estimate paint when you are applying two coats — the standard for an even, durable finish.
Calculator
Free, runs entirely in your browser, and your numbers never leave your device. Results are estimates for planning only.
What this calculator does
Two coats is the standard for an even, durable finish, and it doubles the area your paint must cover. This tool makes the two-coat assumption explicit: it shows the paintable area, doubles it, adds waste, and returns the gallons so you do not run dry partway through the second coat.
How to use it
- Enter the room length, width, and wall height.
- Count the doors and windows to subtract.
- Leave coats at two (the field stays editable if you need one or three).
- Read the gallons sized for the full two-coat job.
The formula
Paintable = 2 × (length + width) × height − openings. Paint = paintable × coats × (1 + waste%) ÷ coverage.
Example calculation
A 12 ft × 14 ft room with 8 ft walls, one door, two windows, two coats at 350 sq ft/gal:
- Wall area: 2 × (12 + 14) × 8 = 416 sq ft
- Openings: 21 + 30 = 51 sq ft
- Paintable: 416 − 51 = 365 sq ft
- Two coats: 365 × 2 = 730 sq ft, +10% ≈ 803 sq ft
- Paint: 803 ÷ 350 ≈ 2.3 gallons
Result: About 2.3 gallons — buy 3 gallons so you have enough for both coats plus touch-ups.
Buying and planning tips
- Buy all the paint for both coats at once, from the same batch, for a consistent color.
- Let the first coat dry fully (check the can's recoat time) before the second.
- The second coat goes faster and uses a bit less paint than the first.
Common mistakes to avoid
- Buying for one coat and running out halfway through the second.
- Recoating too soon, which lifts the first coat and wastes paint.
- Assuming two thin coats use the same paint as one thick coat — they use more.
Assumptions and limits
- Both coats are assumed to cover the full paintable area.
- Each door is 21 sq ft and each window 15 sq ft.
- Coverage of ~350 sq ft per gallon is approximate; primer is separate.
Frequently asked questions
How many coats of paint do I need?
Two coats is the standard for an even, durable finish and is what this calculator assumes. One coat can be enough when repainting a similar color over a sound surface; deep or drastic color changes can need three.
How much paint do I need for two coats?
Take the paintable area, multiply by two, add a waste allowance, and divide by coverage. A typical 12×14 ft room needs about 2 to 3 gallons for two coats.
Why does two coats need about double the paint?
Each coat has to cover the full wall area, so two coats cover roughly twice the square footage — the second coat uses a little less as the surface is sealed.
How long should I wait between coats?
Follow the can's recoat time, usually 2 to 4 hours for latex paint. Recoating too early can pull up the first coat.
Do I always need two coats?
Two coats is the safe default for color changes and bare or patched walls. Repainting a near-identical color over a sound surface can sometimes need just one.
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