Paint Calculator: 24 × 24 ft room
Estimate how many gallons of paint a room needs, with doors and windows subtracted and the number of coats included.
// Bill of materials
Costs are rough, materials only — edit the price to match your quote.
Pre-filled for a 24 × 24 ft room. Change any value to recalculate, or start from scratch.
How it's calculated
Wall area = perimeter × height = 2 × (width + length) × ceiling height. We optionally add the ceiling (width × length), subtract 21 sq ft per door and 15 sq ft per window, multiply by the number of coats, then divide by the paint's coverage per gallon and round up to whole gallons.
Worked example — 24 × 24 ft room
- Room width
- 24 ft
- Room length
- 24 ft
- Ceiling height
- 8 ft
- Surfaces
- Walls only
- Doors
- 1 count
- Windows
- 2 count
- Coats
- 2
- Coverage per gallon
- 350 sq ft
- Paint price
- 35 $/gal
Nearby sizes
| Room size | Gallons to buy | |
|---|---|---|
| 8 × 8 ft room | 2 gallons | Open |
| 8 × 10 ft room | 2 gallons | Open |
| 8 × 12 ft room | 2 gallons | Open |
| 10 × 10 ft room | 2 gallons | Open |
| 10 × 12 ft room | 2 gallons | Open |
| 10 × 14 ft room | 2 gallons | Open |
| 10 × 16 ft room | 3 gallons | Open |
| 12 × 12 ft room | 2 gallons | Open |
| 12 × 14 ft room | 3 gallons | Open |
| 12 × 16 ft room | 3 gallons | Open |
| 12 × 18 ft room | 3 gallons | Open |
| 24 × 24 ft room (this page) | 5 gallons |
Tips for buying paint
- Buy one gallon of primer separately if you're painting over a bold color, patching, or covering bare drywall — topcoat isn't primer.
- One gallon covers about 350 sq ft per coat on smooth, primed walls; rough or porous surfaces drink more, so round generously.
- Two coats is the honest default. A single coat almost never covers evenly, especially with color changes.
- Buy all your paint in one trip so it's from the same batch; mixing batches can leave a visible seam on a long wall.
- Keep the leftover for touch-ups and write the room name and date on the lid with a marker.
- Trim and doors usually need a different (semi-gloss) paint — estimate those separately.
Frequently asked questions
How many gallons of paint do I need for a 12x14 room?
For 8 ft ceilings, walls only, two coats, with a door and two windows subtracted, a 12x14 room needs about 2 gallons. Adding the ceiling pushes it toward 3.
Should I count doors and windows?
Yes — subtract them, or you'll over-buy. We use 21 sq ft per standard door and 15 sq ft per window. Adjust the counts to match your room.
How much does one coat cover?
About 350 sq ft per gallon on smooth primed drywall. Textured, porous or previously-unpainted surfaces can drop that to 250, so lower the coverage figure if your walls are rough.
Do I need primer?
Use primer over bare drywall, big color changes, stains or repairs. It's separate from your topcoat gallons — budget one gallon of primer per ~300 sq ft that needs it.