How Much Paint for a 20x20 Room?
A 20×20 ft room with 8 ft ceilings has 590 sq ft of paintable wall. Two coats take 3.37 gallons, so buy 4 gallons of wall paint. Adding the ceiling brings the total to 5.66 gallons (6 gallons).
Paint needed for a 20x20 room
| Scenario | Paintable area | Exact gallons | Buy |
|---|---|---|---|
| Walls, 1 coat | 590 sq ft | 1.69 | 2 gallons |
| Walls, 2 coats | 590 sq ft | 3.37 | 4 gallons |
| Ceiling, 2 coats | 400 sq ft | 2.29 | 3 gallons |
| Walls + ceiling, 2 coats | 990 sq ft | 5.66 | 6 gallons |
| Walls, 2 coats, 9 ft ceiling | 670 sq ft | 3.83 | 4 gallons |
Assumes 1 door (20 sq ft) and 2 windows (15 sq ft each) deducted, 350 sq ft per gallon, 8 ft ceiling unless stated. Trim and doors not included.
How it is calculated
Walls: 2 × (20 + 20) × 8 = 640 sq ft
Minus door and windows: 640 − 50 = 590 sq ft
Two coats: 590 × 2 ÷ 350 = 3.37 gallons → 4 gallons
Ceiling: 20 × 20 = 400 sq ft → 400 × 2 ÷ 350 = 2.29 gallons
Tips for a 20x20 room
- At 3.37 gallons you are close to bucket territory. Compare 4 gallons against a 5-gallon bucket: the bucket often costs less per gallon and leaves 1.6 gallons for later repairs.
- Cutting in with a brush runs 80 ft along the ceiling line and another 80 ft along the baseboards, before counting door and window frames.
- The 400 sq ft ceiling is large enough to justify a roller extension pole and a dedicated ceiling paint – count on 3 gallons for two coats.
- With 590 sq ft of paintable wall, work in sections and keep a wet edge, otherwise lap marks show on large walls.
Frequently asked questions
How many gallons of paint for a 20x20 room?
With 8 ft ceilings the walls total 2 × (20 + 20) × 8 = 640 sq ft. After deducting 50 sq ft for one door and two windows, 590 sq ft remain. Two coats at 350 sq ft per gallon is 3.37 gallons, so buy 4 gallons. One coat needs 1.69 gallons.
How much paint for the walls and ceiling of a 20x20 room?
The ceiling adds 400 sq ft. Walls plus ceiling, two coats, comes to 5.66 gallons, so buy 6 gallons. The ceiling alone needs 2.29 gallons for two coats.
How much does it cost to paint a 20x20 room?
Paint for the walls (4 gallons) costs roughly $100–$240 at $25–$60 per gallon. With 9 ft ceilings you would need 3.83 gallons, so 4 gallons. Primer, tape and supplies are extra.