How Much Paint for a 10×10 Room?
A 10×10 room with an 8 ft ceiling has 320 sq ft of gross wall area. Subtract a door (20 sq ft) and a window (15 sq ft) and you have 285 sq ft to paint. That is 1 gallon for one coat, 2 gallons for two coats at 350 sq ft/gal.
The worked math for a 10×10×8 room
- Gross wall area: 2 × (10 + 10) × 8 = 320 sq ft
- Subtract 1 door: −20 sq ft
- Subtract 1 window: −15 sq ft
- Paintable area: 320 − 35 = 285 sq ft
- 1 coat at 350 sq ft/gal: 285 ÷ 350 = 0.81 gal → buy 1 gallon
- 2 coats at 350 sq ft/gal: 285 × 2 ÷ 350 = 1.63 gal → buy 2 gallons
Adjust the calculator below for your actual door/window count, ceiling height, or texture.
Room Dimensions
Openings & Coats
How the math works
Step 1 — gross wall area
gross_wall = 2 × (length + width) × ceiling_height Step 2 — subtract openings
paintable = gross_wall − (doors × 20) − (windows × 15) Each standard 36×80 in door = 20.0 sq ft. Average window = 15 sq ft (industry convention). Paintable area is clamped to ≥0.
Step 3 — gallons
gallons_to_buy = ⌈ (paintable × coats) ÷ coverage ⌉ Coverage defaults to 350 sq ft/gal — the conservative figure used by Sherwin-Williams, Benjamin Moore and Behr field guides. Always round up to whole gallons; running out mid-job risks a dye-lot mismatch.
10×10 vs 12×12: how much more paint?
A 12×12 room has 384 sq ft gross wall area vs 320 sq ft for a 10×10 — 20% more wall area. After standard openings, the 12×12 room needs 334 sq ft painted vs 285 sq ft for the 10×10. Both rooms fit within the same gallon tiers (1 gal / coat, 2 gal for 2 coats) at 350 sq ft/gal because both are under 350 sq ft paintable per coat.
The 10×10 room is the smallest common bedroom size. A small nursery or home office of 10×10 is one of the most economical paint jobs — typically requiring only 1 gallon of topcoat per coat.
Frequently Asked Questions
A 10×10×8 room with 1 door and 1 window has 320 sq ft gross wall area. Subtract 20 sq ft (door) + 15 sq ft (window) = 285 sq ft paintable. Two coats at 350 sq ft/gal: 285 × 2 ÷ 350 = 1.63 gallons → buy 2 gallons.
Yes — one coat only. At 350 sq ft/gal, one coat of 285 sq ft needs 0.81 gallons → buy 1 gallon. But one coat rarely gives even, durable coverage. Most pros recommend two coats, which requires 2 gallons for a 10×10 room.
At 250 sq ft/gal (typical primer), 285 sq ft paintable area needs 285 ÷ 250 = 1.14 gallons → buy 2 gallons of primer. At 300 sq ft/gal (sealed surface): 0.95 gallons → buy 1 gallon. Use the primer calculator on this site for your specific situation.
Gross wall area = 2 × (10 + 10) × 8 = 2 × 20 × 8 = 320 sq ft. This is before subtracting doors and windows. The formula is perimeter × ceiling height: (2L + 2W) × H.