Wall Paint Calculator
To paint a 20 × 10 ft wall (200 sq ft) with two coats, you need about 220 sq ft of coverage after a 10% touch-up allowance — 2 gallons, based on 350 sq ft of coverage per gallon for one coat (175 sq ft per gallon for two coats). Subtract the area of any doors or windows in the wall first.
Reviewed by The ponderloop teamUpdated 2026-07-11How we calculate
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0 sq ft + 0% waste = 0 sq ft
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How this number is calculated
0 sq ft (no waste added) ÷ 175 sq ft per gallon = 0 gallons
Shopping list
- Interior wall paint (1 gallon)
- Paint roller kit (roller, tray, covers)
- Angled sash paintbrush (2.5 inch)
- Painter's tape
- Canvas drop cloth
- Paint tray liners
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Methodology & assumptions
Wall area is wall width times wall height, minus any door/window openings, using this tool's inputs directly. That area is divided by coverage per gallon — a 350 sq ft/gal baseline for one coat of mid-sheen interior latex, halved for two coats and reduced further for additional coats — then multiplied by your chosen waste percentage and rounded up to the next whole gallon.
- Manufacturer coverage specs (~350 sq ft/gal, one coat, mid-sheen interior latex)
- Typical US interior wall paint retail price range, 2026
Worked examples
| Room | Result |
|---|---|
| 20 × 10 ft wall, 2 coats, +10% touch-up waste | 200 sq ft + 10% waste ≈ 220 sq ft → 2 gallons |
| 12 × 9 ft wall, 1 coat (same-color refresh), exact | 108 sq ft, exact (0% waste) → 1 gallon |
| 15 × 9 ft wall, 3 coats (dark accent color), +10% waste | 135 sq ft + 10% waste ≈ 148.5 sq ft → 2 gallons |
Frequently asked questions
- How many gallons of paint do I need for a wall?
- Multiply the wall width by its height in feet to get the square footage, subtract the area of any doors or windows, then divide by the coverage per gallon for your number of coats. One coat covers about 350 sq ft per gallon; two coats effectively halve that to about 175 sq ft per gallon, since you are covering the same wall twice.
- Where does the 350 sq ft per gallon figure come from?
- It is the standard coverage rate printed on most mid-sheen interior latex paint cans for a single coat on a smooth, primed wall. This calculator uses it as the baseline and divides it by your number of coats to get effective coverage per gallon.
- Why does coverage drop so much with a second or third coat?
- Each coat uses roughly the same amount of paint per sq ft, so painting a wall twice uses about twice the paint. Entering 2 in the Coats field halves the effective coverage to 175 sq ft per gallon; entering 3 (for a dark or dramatic color change) drops it to about 117 sq ft per gallon.
- What surfaces need more paint than the 350 sq ft/gal baseline?
- Rough, textured, or porous surfaces (unprimed drywall, stucco, brick, or heavily patched walls) soak up more paint per sq ft and can cut real coverage well below 350 sq ft per gallon. Painting a dark existing wall a much lighter color, or a light wall a saturated dark color, often needs an extra coat to fully hide the old color, even beyond what a standard 2-coat estimate accounts for.
- Should I round up or buy an extra gallon of wall paint?
- Always round up to the next full gallon. Paint is mixed and tinted in batches, so running short mid-wall and needing a rush re-tint risks a visible sheen or color mismatch where the two batches meet.