How Much Paint for a 18x18 Room?
A 18×18 ft room with 8 ft ceilings has 526 sq ft of paintable wall. Two coats take 3.01 gallons, so buy 4 gallons of wall paint. Adding the ceiling brings the total to 4.86 gallons (5 gallons).
Paint needed for a 18x18 room
| Scenario | Paintable area | Exact gallons | Buy |
|---|---|---|---|
| Walls, 1 coat | 526 sq ft | 1.5 | 2 gallons |
| Walls, 2 coats | 526 sq ft | 3.01 | 4 gallons |
| Ceiling, 2 coats | 324 sq ft | 1.85 | 2 gallons |
| Walls + ceiling, 2 coats | 850 sq ft | 4.86 | 5 gallons |
| Walls, 2 coats, 9 ft ceiling | 598 sq ft | 3.42 | 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 × (18 + 18) × 8 = 576 sq ft
Minus door and windows: 576 − 50 = 526 sq ft
Two coats: 526 × 2 ÷ 350 = 3.01 gallons → 4 gallons
Ceiling: 18 × 18 = 324 sq ft → 324 × 2 ÷ 350 = 1.85 gallons
Tips for a 18x18 room
- At 3.01 gallons you are close to bucket territory. Compare 4 gallons against a 5-gallon bucket: the bucket often costs less per gallon and leaves 2 gallons for later repairs.
- Cutting in with a brush runs 72 ft along the ceiling line and another 72 ft along the baseboards, before counting door and window frames.
- The 324 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 526 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 18x18 room?
With 8 ft ceilings the walls total 2 × (18 + 18) × 8 = 576 sq ft. After deducting 50 sq ft for one door and two windows, 526 sq ft remain. Two coats at 350 sq ft per gallon is 3.01 gallons, so buy 4 gallons. One coat needs 1.5 gallons.
How much paint for the walls and ceiling of a 18x18 room?
The ceiling adds 324 sq ft. Walls plus ceiling, two coats, comes to 4.86 gallons, so buy 5 gallons. The ceiling alone needs 1.85 gallons for two coats.
How much does it cost to paint a 18x18 room?
Paint for the walls (4 gallons) costs roughly $100–$240 at $25–$60 per gallon. With 9 ft ceilings you would need 3.42 gallons, so 4 gallons. Primer, tape and supplies are extra.