How Paint Coverage Works
Paint coverage refers to how much surface area a gallon of paint can coat. Most interior latex paints cover approximately 350 to 400 square feet per gallon on smooth, sealed surfaces with a single coat. This coverage rate depends on the paint quality, surface texture, color, and application method.
Understanding paint coverage is essential for budgeting and purchasing the right amount of paint. Buying too little means interrupted work and potential color mismatches between batches. Buying too much wastes money and creates disposal issues. This calculator accounts for standard deductions for doors and windows to give you an accurate estimate.
Paint Calculation Formula
Standard deductions: Door = 21 sq ft (3 × 7 ft), Window = 15 sq ft (3 × 5 ft average).
Coverage by Paint Type
| Paint Type | Coverage (sq ft/gallon) | Dry Time |
|---|---|---|
| Interior Latex (flat) | 350–400 | 1–2 hours |
| Interior Latex (satin/eggshell) | 350–400 | 1–2 hours |
| Interior Latex (semi-gloss) | 350–400 | 2–4 hours |
| Exterior Latex | 250–350 | 4–6 hours |
| Oil-Based | 350–450 | 6–8 hours |
| Primer | 250–350 | 1–2 hours |
How Many Coats Do You Need?
- 1 coat: Same color touch-up or high-quality paint over similar color
- 2 coats: Standard for most projects; provides even coverage and durability
- 3 coats: Dramatic color changes (dark to light), covering stains, or high-traffic areas
Paint Buying Tips
- Always buy 10–15% more than calculated to account for touchups and waste
- Higher quality paint often provides better coverage, potentially needing fewer coats
- Textured surfaces (stucco, brick) may require 20–30% more paint
- Keep leftover paint for future touch-ups, stored in a cool, dry place
- Consider primer as a separate purchase for bare surfaces or major color changes
Worked Example
A room 15 × 12 ft with 8 ft ceilings, 2 doors and 2 windows, 2 coats:
Wall Area = 54 × 8 = 432 sq ft
Openings = (2 × 21) + (2 × 15) = 72 sq ft
Paintable = 432 − 72 = 360 sq ft
Paint = 360 × 2 ÷ 350 = 2.06 gallons (buy 3)
Frequently Asked Questions
How much does a gallon of paint cover?
A gallon of standard interior latex paint covers approximately 350 to 400 square feet per coat on smooth, previously painted surfaces. Rough or porous surfaces may reduce coverage to 250 to 300 square feet per gallon.
Do I need primer before painting?
Primer is recommended for bare drywall, wood, or metal; for surfaces with stains; when making dramatic color changes; and when painting over glossy surfaces. Many modern paints include primer (paint-and-primer-in-one), which can eliminate the separate primer step for less demanding applications.
Should I buy quarts or gallons?
Gallons are more cost-effective per square foot of coverage. Buy gallons when you need more than 1.5 quarts, as a gallon typically costs less than 2 quarts combined. Quarts are suitable for accent walls, small bathrooms, or trim work.
How long does paint last in the can?
Unopened latex paint lasts up to 10 years; opened cans last 2 to 5 years if properly sealed. Oil-based paint lasts up to 15 years unopened. Store paint in a cool, dry place away from extreme temperatures. If paint has a foul odor or lumps that do not dissolve with stirring, it should be discarded.