Gallons for 400 sq ft walls at 2 coats?
About 2.3 gallons at 350 sq ft/gal before waste buffer.
Paint quantity is **net surface area × coats ÷ coverage rate**, with coverage read from the paint can label.
**Formula (imperial):**
Gallons = (Net sq ft × Coats) ÷ Coverage (sq ft per gallon per coat) × (1 + waste%)
**Example — 400 sq ft walls, 2 coats, 350 sq ft/gal, 10% waste:**
(400 × 2) ÷ 350 × 1.10 = **2.51 gallons**
**Example — 12×12 ft wall area (144 sq ft), 2 coats, 350 sq ft/gal:**
(144 × 2) ÷ 350 = **0.82 gallons** (under one gallon)
Subtract **doors** (~21 sq ft each) and **windows** (~15 sq ft each) from gross wall area before calculating. Textured, porous, or unprimed surfaces need a lower coverage number (250–300 sq ft/gal).
Concise answers for common searches — definitions, steps, and comparisons.
About 2.3 gallons at 350 sq ft/gal before waste buffer.
About 21 square feet per door.
The calculator multiplies net paintable area by coats, divides by label coverage rate, and applies an optional waste buffer.
Formula
gal = (net_sq_ft × coats ÷ sq_ft_per_gal) × (1 + waste% / 100)Tap 12×12 bedroom, 400 sq ft walls, or accent wall — or enter your own dimensions on the main form.
Tap Walls · 2 coats, Ceiling · 1 coat, Primer, or Porous surface — each sets coverage and coats.
Imperial: sq ft per gallon per coat. Metric: m² per liter per coat — read from the label.
Enable deductions on the main form — default counts subtract standard opening sizes.
Results show paint to order, base gallons, best retail can fit, and 1 / 2 / 5 gal round-up table.
After walls, estimate LVP or laminate cartons with Flooring Calculator for the same room.
Input
400 sq ft · 2 coats · 10% wasteOutput
≈ 2.51 gal(400×2)/350×1.10 = 2.51 gallons.
Input
12×12 ft · 2 coatsOutput
≈ 0.82 galGolden test vector — under one gallon.
Input
300 sq ft · 400 sq ft/galOutput
0.75 galFlat ceiling — single coat.
Common real-world scenarios where this tool saves time.
400 sq ft walls, 2 coats at 350 sq ft/gal ≈ 2.3 gal — two 1-gal cans plus a quart.
80 sq ft feature wall, 2 coats ≈ 0.46 gal — one quart may suffice.
300 sq ft/gal, 1 coat — porous board absorbs more than finish paint.
35 m² at 8.5 m²/L per coat, 2 coats — matches EU paint can labels.
Step-by-step chains that connect related tools for common tasks.
From wall area to gallons.
| Surface | Coverage range |
|---|---|
| Smooth primed drywall | 350–400 |
| Textured drywall | 250–300 |
| Porous brick / stucco | 200–250 |
| Flat ceiling | 400 |
| Factor | Paint | Wallpaper |
|---|---|---|
| Typical waste | 10% cut-in buffer | 10–15% pattern match |
| Skill level | Moderate DIY | Higher — pattern alignment |
| Remodel speed | 2 coats + dry time | Strip prep + hang time |
Same color code can shift between batches — one purchase avoids visible seams.
Pigments settle — mix thoroughly for consistent sheen and color.
Paintable **wall** area is usually much larger than floor area — measure walls or use total sq ft mode.
Most interior jobs need **two finish coats** — double the single-coat gallon count.
Brick, stucco, and unprimed drywall need **250–300 sq ft/gal** — not 400.
Tinted paint varies by batch — buy enough from **one mix** for the whole room.
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Multiply paintable square footage by number of coats, divide by coverage sq ft per gallon from your can, then add 10% waste. Example: 400 sq ft × 2 coats ÷ 350 = 2.29 gal.
If walls total about 400 sq ft paintable area at 2 coats and 350 sq ft/gal: roughly 2.3 gallons. Floor size alone (144 sq ft) is not wall area — measure walls or enter total sq ft.
At 350 sq ft per gallon per coat, one coat covers 350 sq ft — about 0.0029 gallons per sq ft per coat.
Yes for whole-room estimates — each standard door is ~21 sq ft and window ~15 sq ft. Accent walls with no openings can skip deductions.
Most interior walls need two finish coats. New drywall often needs primer plus two finish coats — run primer as a separate calculation with primer coverage (~300 sq ft/gal).
10% covers cut-ins, roller overlap, and touch-ups. Porous surfaces or strong color changes may need 15%.
Multiply gallons by 3.785. The calculator shows both when metric mode is selected.
Flat ceiling paint often covers ~400 sq ft/gal in one coat. Use the Ceiling · 1 coat preset or adjust coverage on the can label.
Use the Primer · 1 coat preset (~300 sq ft/gal) on the same wall area before calculating finish coats separately.
Yes — enter exterior wall sq ft and the coverage rate from your exterior can. Textured siding needs lower coverage numbers.
Room dimensions and paint inputs stay on your device — EverydayTools does not transmit paint calculator data to remote servers.
Estimates only — not professional painting advice. Verify coverage on your paint can for surface type and application method.
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Reviewed on 2026-06-27.
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350 sq ft/gal — smooth primed drywall
Standard door ≈ 21 sq ft (3×7 ft)
Standard window ≈ 15 sq ft (3×5 ft)
Read from the paint can — smooth drywall is often 350–400 sq ft per gallon per coat.
Coverage reference (verify your can label)
| Surface | Typical coverage |
|---|---|
| Smooth primed drywall | 350–400 sq ft / gal / coat |
| Textured drywall | 250–300 sq ft / gal / coat |
| Porous brick or stucco | 200–250 sq ft / gal / coat |
| Flat ceiling | 400 sq ft / gal / coat |
| Previously painted (repaint) | 350 sq ft / gal / coat |