How much paint do you need?
Get a practical paint estimate for your walls or ceiling. Add your room measurements and see the amount, coverage, and cost update instantly.
Room measurements
Your estimate
Buy this amount for 2 coats on the walls.
- Paintable area
- 334 ft²
- Area across all coats
- 668 ft²
- Exact paint needed
- 2.1 gal
- Estimated paint cost
- $120
Upload a room photo and try a new look
Planning estimate only. Actual coverage varies by paint, surface texture, color change, and application method. Check the coverage printed on your paint can before buying.
How the paint estimate works
The calculator finds your four walls from the room perimeter, removes the openings you are not painting, and then accounts for every coat.
Wall area = 2 × (length + width) × height
Paintable area = wall area − doors − windows
Paint needed = paintable area × coats ÷ coverage
Openings deducted
The estimate removes 20 ft² per door and 15 ft² per window.
Coverage adjustable
Use the exact coverage printed on your paint can for a closer estimate.
Paint estimates for common room sizes
These examples assume two coats, 350 ft² of coverage per gallon, standard 20 ft² doors and 15 ft² windows, and a 10% touch-up allowance. Opening counts are shown for each example.
| Room | Dimensions | Openings | Paintable area | Paint to buy |
|---|---|---|---|---|
| Bathroom | 8 × 10 × 8 ft | 1 door · 1 window | 253 ft² | 2 gal1.6 gal exact |
| Small bedroom | 10 × 10 × 8 ft | 1 door · 1 window | 285 ft² | 2 gal1.8 gal exact |
| Nursery | 10 × 12 × 8 ft | 1 door · 2 windows | 302 ft² | 2 gal1.9 gal exact |
| Home office | 10 × 12 × 8 ft | 1 door · 1 window | 317 ft² | 2 gal2.0 gal exact |
| Bedroom | 12 × 12 × 8 ft | 1 door · 2 windows | 334 ft² | 3 gal2.1 gal exact |
| Dining room | 12 × 14 × 8 ft | 1 door · 2 windows | 366 ft² | 3 gal2.3 gal exact |
| Hallway | 4 × 12 × 8 ft | 4 doors · 0 windows | 176 ft² | 2 gal1.1 gal exact |
| Primary bedroom | 14 × 16 × 9 ft | 2 doors · 3 windows | 455 ft² | 3 gal2.9 gal exact |
| Living room | 16 × 20 × 9 ft | 2 doors · 3 windows | 563 ft² | 4 gal3.5 gal exact |
| Great room | 20 × 24 × 10 ft | 2 doors · 4 windows | 780 ft² | 5 gal4.9 gal exact |
Make the estimate more accurate
Check the label
Coverage varies by paint formula. Replace the default with the number printed on the can.
Account for the surface
Fresh drywall, masonry, heavy texture, and unprimed walls usually absorb more paint.
Plan for the color change
Moving from very dark to very light—or the reverse—can require primer or another coat.
Keep one batch
Buy enough paint at once when possible so the color and sheen stay consistent across the room.
See the color in your actual room before you paint.
Upload a room photo, choose an interior style, and create a new version of your space with RoomGen.
Redesign my roomPaint calculator FAQ
How much paint do I need for a room?+
Measure the room length, width, and ceiling height. Wall area is the room perimeter multiplied by height. Subtract doors and windows, multiply by the number of coats, then divide by the coverage shown on your paint can. RoomGen calculates each step and rounds up to a practical amount to buy.
How much area does one gallon of paint cover?+
A gallon of interior paint commonly covers about 350 to 400 square feet for one coat on a smooth, prepared surface. Porous walls, heavy texture, dramatic color changes, and some application methods can reduce coverage. Always use the figure printed on the product you plan to buy.
Should I subtract doors and windows?+
Yes, when you are not painting them. This calculator subtracts 20 square feet for each standard door and 15 square feet for each average window. For unusually large openings, calculate their actual area and adjust your room dimensions or coverage allowance.
Do I need one coat or two coats of paint?+
Two coats are a dependable planning assumption for an even finish. One coat may work when refreshing a similar color with a high-quality paint. Major color changes, new drywall, stains, or porous surfaces may also need a separate primer.
Why does the calculator add extra paint?+
The optional 10 percent allowance covers roller and brush loss, small measuring differences, and paint kept for future touch-ups. Turn it off when you need the raw mathematical estimate.
Does the paint calculator save my measurements?+
No. The calculation runs in your browser and does not upload or store the room measurements you enter.