Paint Calculator
Find out how much paint you need for a room or wall: subtract doors and windows, set your paint's coverage rate and number of coats, and get the result in gallons and liters.
Result
| Net paintable area | |
| Paint per coat | |
| Buy (rounded up) |
Units & conversions used
Imperial inputs are square feet and ft² per gallon; results are shown in gallons and liters (1 gal = 3.78541 L). Metric inputs are converted first: 1 m² = 10.7639 ft², and m²/L is converted to ft²/gal by multiplying by 10.7639 × 3.78541 (so 8.6 m²/L ≈ 350 ft²/gal).
Formula & source
gallons per coat = net area ÷ coverage (ft²/gal)
gallons total = gallons per coat × coats
Source: basic area subtraction and division — no authority needed. The default coverage of 350 ft²/gal is a typical value for interior latex paint: manufacturers generally list 250–400 ft²/gal on the can, so treat the default as a starting estimate and enter the number printed on your actual paint. Buy quantity is rounded up to whole gallons, since paint is sold by the gallon.
Worked example (you can verify by hand)
Input: 12×14 ft room, 8 ft ceiling → wall area 416 ft²; one door 21 ft² + windows 15 ft²; coverage 350 ft²/gal; 2 coats.
- Wall area: 2 × (12 + 14) × 8 = 416 ft²
- Net area: 416 − 21 − 15 = 380 ft²
- Per coat: 380 ÷ 350 = 1.0857 gal
- Total: 1.0857 × 2 = 2.1714 gal → 2.17 gal (8.22 L)
Expected output: 2.17 gal total — buy 3 gallons (rounded up).
Limitations — what this cannot do
- This estimates topcoat quantity only. It does not include primer — a separate primer coat is common when painting over bare drywall, stains, or dark colors.
- Rough, porous or textured surfaces (stucco, brick, unprimed drywall) absorb more paint than the can's rated coverage; reduce the coverage number in that case.
- Dramatic color changes (dark to light) often need an extra coat beyond what is entered here.
- Ceilings, trim and closets are not included — measure and add them separately if you plan to paint them.
How much does it cost to paint a house?
Professional painting is mostly labor — paint itself is typically only 15–25% of the bill. Commonly published US ranges for 2025–2026 (labor + materials) are:
| Job | Typical range (per ft² of floor area) | Example: 2,000 ft² home |
|---|---|---|
| Interior repaint | $2–$6 / ft² | $4,000–$12,000 |
| Exterior repaint | $1.50–$4 / ft² | $3,000–$8,000 |
These are broad planning ranges, not quotes. What moves you within (or beyond) the range:
- Labor market — the single biggest variable; rates differ sharply by metro area.
- Prep work — patching, sanding, caulking and priming stained or damaged walls add hours.
- Height and access — vaulted ceilings, stairwells and multi-story exteriors need scaffolding or lifts.
- Paint quality and coats — premium paint and extra coats cost more but last longer.
- Color change — dark-to-light usually needs an extra coat.
To budget the material side, use the calculator at the top of this page to find your gallons, then multiply by your paint's per-gallon price ($25–$70+ for quality interior latex). DIY saves the labor portion but not the paint cost.
FAQ
How much paint do I need for a 12×14 ft bedroom?
With 8 ft ceilings the walls total 416 ft². Subtracting one door (21 ft²) and windows (15 ft²) leaves 380 ft², which needs about 2.17 gallons for two coats at 350 ft²/gal — so buy 3 gallons.
What does "one gallon covers 350 square feet" mean?
It means one gallon covers roughly 350 ft² of smooth surface with one coat. It is a manufacturer rating for ideal conditions; always check your specific paint can, where the rating is usually printed as a range like 250–400 ft²/gal.
Should I subtract doors and windows from the wall area?
Yes — subtracting them gives the true paintable area. If you skip them, the leftover paint simply becomes your margin for touch-ups and waste, which many DIY painters do on purpose.
How many coats of paint do I need?
Two coats is the standard recommendation for even color and durability. One coat over primer can work for repainting a similar color; a third coat is sometimes needed for drastic color changes.
Does paint sheen affect how much I need?
Not much — coverage ratings are similar across sheens. Surface condition matters far more: porous or rough walls can use noticeably more paint than the rated coverage.