How many gallons of paint for a 20×20 room?
Quick Answer
A 20×20 room with 8-foot ceilings requires about 3 gallons of wall paint for two coats (after deducting doors and windows) and 1 gallon for the ceiling. Plan on 4 gallons total for a complete two-coat paint job including ceiling, or 2 gallons for walls only.
Quick Reference Table
| Area painted | Paint for 20×20 room (8 ft ceilings) |
|---|---|
| Walls only, 1 coat | 1.5 gallons |
| Walls only, 2 coats | 3 gallons |
| Ceiling only, 1 coat | 0.6 gallons |
| Ceiling only, 2 coats | 1.2 gallons |
| Walls + ceiling, 2 coats | ~4 gallons |
How to Calculate It Yourself
- 1
Wall area: perimeter 80 ft × 8 ft ceiling = 640 sq ft.
- 2
Subtract doors (2 × 20 sq ft = 40 sq ft) and windows (3 × 15 sq ft = 45 sq ft): 640 − 85 = 555 sq ft.
- 3
At 350 sq ft per gallon: 555 ÷ 350 = 1.58 gallons per coat → 3.2 gallons for 2 coats.
- 4
Ceiling: 20 × 20 = 400 sq ft ÷ 350 = 1.14 gallons per coat → 2.3 gallons for 2 coats.
- 5
Total: 3.2 + 2.3 = 5.5 gallons for walls + ceiling, 2 coats. Buy 6 gallons.
Pro Tip
If changing from dark to light color, you may need a primer coat first, adding another gallon. Buying 5-gallon pails saves 20–30% vs. buying individual gallons.
Assumptions to Check
Before ordering materials, confirm the dimensions, product coverage, waste factor, and local installation requirements for your project. Manufacturer coverage tables and local code rules can change the final quantity, especially for structural work, exterior projects, and irregular layouts.
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