How Much Paint for a 15x20 Room?
A 15×20 ft room with 8 ft ceilings has 510 sq ft of paintable wall. Two coats take 2.91 gallons, so buy 3 gallons of wall paint. Adding the ceiling brings the total to 4.63 gallons (5 gallons).
Paint needed for a 15x20 room
| Scenario | Paintable area | Exact gallons | Buy |
|---|---|---|---|
| Walls, 1 coat | 510 sq ft | 1.46 | 2 gallons |
| Walls, 2 coats | 510 sq ft | 2.91 | 3 gallons |
| Ceiling, 2 coats | 300 sq ft | 1.71 | 2 gallons |
| Walls + ceiling, 2 coats | 810 sq ft | 4.63 | 5 gallons |
| Walls, 2 coats, 9 ft ceiling | 580 sq ft | 3.31 | 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 × (15 + 20) × 8 = 560 sq ft
Minus door and windows: 560 − 50 = 510 sq ft
Two coats: 510 × 2 ÷ 350 = 2.91 gallons → 3 gallons
Ceiling: 15 × 20 = 300 sq ft → 300 × 2 ÷ 350 = 1.71 gallons
Tips for a 15x20 room
- You need 2.91 gallons, so 3 gallons leaves about 0.3 quarts spare – enough for touch-ups. Do not bother with a 5-gallon bucket.
- Cutting in with a brush runs 70 ft along the ceiling line and another 70 ft along the baseboards, before counting door and window frames.
- The 300 sq ft ceiling is large enough to justify a roller extension pole and a dedicated ceiling paint – count on 2 gallons for two coats.
- With 510 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 15x20 room?
With 8 ft ceilings the walls total 2 × (15 + 20) × 8 = 560 sq ft. After deducting 50 sq ft for one door and two windows, 510 sq ft remain. Two coats at 350 sq ft per gallon is 2.91 gallons, so buy 3 gallons. One coat needs 1.46 gallons.
How much paint for the walls and ceiling of a 15x20 room?
The ceiling adds 300 sq ft. Walls plus ceiling, two coats, comes to 4.63 gallons, so buy 5 gallons. The ceiling alone needs 1.71 gallons for two coats.
How much does it cost to paint a 15x20 room?
Paint for the walls (3 gallons) costs roughly $75–$180 at $25–$60 per gallon. With 9 ft ceilings you would need 3.31 gallons, so 4 gallons. Primer, tape and supplies are extra.