Paint coverage: from sq ft to gallons and buckets
By Srikanta M · Updated 2026-09-26 · 7 min read · Formula v1.0.0 verified 2026-09-10
Divide net sq ft by the bucket coverage (ft²/gal per coat), multiply by coats and add 10% waste. 400 sq ft at 410 ft²/gal and 2 coats gives 2.0 gal net, 2.2 gal with waste: 2 one-gallon buckets plus a quart.
What does the coverage figure mean?
The data-sheet ft²/gal applies to each coat, not the job total. A bucket rated 410 ft²/gal covers 410 sq ft once; two coats over 400 sq ft take about 2 gallons.
Always use the bucket you will buy. Figures here are central guides for estimating before choosing a brand.
net_gal = sq_ft ÷ coverage × coats; buy = net × (1 + waste)
How far does a gallon go by surface?
Porosity rules. Smooth primed drywall takes about 410 ft²/gal per coat. Textured, brick or unprimed render take far less.
Guide coverage by surface (matte emulsion, per coat)
| Surface | ft² per gallon | m² per litre |
|---|---|---|
| Smooth wall (plaster, drywall) | 407 | 10 |
| Primed wood | 367 | 9 |
| Bare concrete | 326 | 8 |
| Textured wall | 285 | 7 |
| Bare brick | 244 | 6 |
| Porous render, unprimed | 204 | 5 |
How many coats go in the math?
Two coats is standard for a color change. One coat only holds for same-color repaints in good shape.
Quoting one coat and needing two doubles material and adds 60–70% labor.
- Same color, good shape: 1 coat (check hiding on a 20 sq ft test).
- Color change or new surface: 2 coats.
- White over deep color: 2 coats plus primer.
How do you round to buckets?
Stores sell sealed buckets: divide buy gallons by bucket size and round up. 2.2 gal in 1-gal buckets means 3 buckets (one stays nearly full for touch-ups).
Keep touch-up stock: half a gallon saved beats buying a full bucket for a scuff.
buckets = ceil(buy ÷ bucket_size)
Worked example: 400 sq ft, 2 coats, 410 ft²/gal
- Net: 400 ÷ 410 × 2 = 1.95 gal
- Buy with 10%: 1.95 × 1.10 = 2.15 gal
- 1-gal buckets: ceil(2.15) = 3 buckets
→ 3 one-gallon buckets (3 gal on site, spare for touch-ups).
Common mistakes
- Reading coverage as a job total instead of per coat: 400 sq ft at 410 ft²/gal is not 1 gallon, it is 2 at two coats.
- Skipping door and window deductions first: 40 sq ft of openings saves nearly a quart at two coats.
- Ordering exact gallons with no touch-up can: a 0.1 gal scuff forces a full-bucket buy.
From calculation to quote
Add labor, overhead and your margin, and generate the professional PDF.
FAQs
- How far does a 5-gallon bucket go?
- At 410 ft²/gal and 2 coats, about 1,025 sq ft per bucket (5 × 410 ÷ 2). On texture at 285 ft²/gal, about 712 sq ft. Always divide capacity by coats.
- Does texture drink much more paint?
- About 40% more than smooth: 400 sq ft at two coats takes 2.0 gal smooth and 2.8 gal textured. Prime thirsty surfaces first.
- Does primer count as a coat?
- No in the finish math: primer seals and can save a finish coat, but it is quoted as its own line (about 330–410 ft²/gal).
- More waste on ceilings?
- Yes, 12% with roller on stipple or heavy cut-ins: spatter and roller loading raise loss over walls.
- How does this flow into the quote?
- Add to quote from the calculator: quantity travels in buckets with price. Labor per sq ft goes as a second line.
Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.