Paint calculator: how much paint do I need?
Enter the room, the openings and your prices. You get paintable square feet, gallons (split into 5-gallon buckets and single gallons) and a rough job price. Everything stays in your browser.
Your estimate
- Wall area (after doors and windows)
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- Ceiling area
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- Total paintable area
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- Wall paint
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- Buy as
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- Ceiling paint
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- Buy as
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- Paint cost
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- Labor (rough)
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- Rough job total
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Estimates only. Gallons are rounded up for each surface. Real jobs vary with surface texture, color changes, primer and waste, so check before you buy or quote.
How to measure a room for paint
- Measure the length and width of the room along the floor, wall to wall, in feet. Round up to the next half foot.
- Measure the wall height from the floor to the ceiling. Most rooms are 8, 9 or 10 feet.
- Count the doors and windows. Standard sizes are used here; for big openings like sliders or garage doors, count them as two or three.
- Pick the number of coats. Two coats is typical for a color change or new work; one coat can be enough for a refresh in the same color.
How much paint by room size
8-foot walls, 1 door, 1 window, 2 coats, 350 sq ft per gallon. Computed with the same formula as the calculator above.
| Room (ft) | Wall area | Wall paint | Ceiling paint |
|---|---|---|---|
| 10 × 10 | 285 sq ft | 2 gal | 1 gal |
| 10 × 12 | 317 sq ft | 2 gal | 1 gal |
| 12 × 12 | 349 sq ft | 2 gal | 1 gal |
| 12 × 14 | 381 sq ft | 3 gal | 1 gal |
| 14 × 16 | 445 sq ft | 3 gal | 2 gal |
| 16 × 20 | 541 sq ft | 4 gal | 2 gal |
About paint coverage
Coverage is printed on every can, usually as a range in square feet per gallon. Smooth, already-painted walls are at the high end of that range. Textured, porous or patched walls soak up more paint, so use a lower number in the coverage field for those.
Ceilings usually get a different paint than walls, so the calculator counts them separately. Trim, doors and cabinets are not included; price those as their own line items.
Do you need primer?
Plan on primer for new drywall, large patches, stains, bare wood, glossy surfaces and big color changes (for example dark to light). Primer has its own coverage on the label. To estimate it, run the calculator again with 1 coat and the primer’s coverage.
Questions
How many gallons of paint do I need for a 12 × 12 room?
With 8-foot walls, one door, one window and two coats at 350 sq ft per gallon, the walls are about 349 sq ft and you need about 2 gallons. Add about 1 gallon if you also paint the ceiling. Use the calculator above for your exact numbers.
Should I subtract doors and windows?
Yes, for a closer number. This calculator subtracts about 20 sq ft per door and 15 sq ft per window. If the room has only a few small openings, some painters skip this step and keep the extra paint for touch-ups.
When should I buy 5-gallon buckets instead of single gallons?
For bigger jobs a 5-gallon bucket is usually cheaper per gallon and keeps the color consistent. The calculator shows how many buckets and single gallons cover the amount you need; compare prices at your supplier.
How do I price labor for a paint job?
Painters commonly charge per square foot of paintable surface, per hour, or a flat price per room. Use your own rates. The labor number here is only a rough guide and does not include prep, repairs, trim, travel or overhead.
Is this calculator free? Does it save my numbers?
Yes, it is free and needs no sign-up. Nothing is saved or sent anywhere; the math runs in your browser and is gone when you close the page.
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