Paint Coverage Explained — How Much Paint Do You Really Need?
Every paint can says "covers 350–400 sq ft per gallon." But that number assumes one coat, smooth drywall, and a roller — not two coats on textured walls with a brush. Most DIYers buy 30% too much paint because they don't account for the real-world differences.
The Industry Standard — and Why It's Wrong for You
The 350 sq ft/gallon number comes from ideal lab conditions: one coat, sprayed, on primed drywall. Your actual coverage depends on:
- Surface texture: Stucco or brick eats 40–50% more paint than smooth drywall
- Color change: Going from dark to light needs 2–3 coats instead of 1–2
- Sheen: Flat paint covers more (less binder, more pigment). Semi-gloss covers less
- Application method: Rolling uses 10–15% more than spraying
Calculate Your Wall Area
Total wall area = perimeter × ceiling height. For a 12×10 room with 8-foot ceilings: (12+10+12+10) × 8 = 352 sq ft. Then subtract doors (20 sq ft each) and windows (15 sq ft each).
Why Two Coats (Almost Always)
One coat leaves thin spots and uneven color — especially with sheen paints. The second coat provides the uniform finish you paid for. Exception: repainting the same color on a clean, well-maintained wall. One coat may be enough there.
Estimate Your Paint Needs
Use the calculator below. Enter your room dimensions, number of doors/windows, coats, and local paint price.
Sheen Guide — Where to Use What
| Sheen | Best For | Coverage Impact |
|---|---|---|
| Flat | Ceilings, low-traffic walls | Best coverage |
| Eggshell | Living rooms, bedrooms | Good |
| Satin | Kitchens, bathrooms, hallways | -10% vs flat |
| Semi-Gloss | Trim, doors, cabinets | -15% vs flat |
Stop guessing and start measuring. Use the calculator above, or browse our full list of 18 calculators for your next project.