How this calculator works
This runs our exterior paint calculator and caulk calculator. The surface is the walls (the perimeter times the wall height times the stories) plus the gable triangles, less the windows and doors. Paint is that area times the coats divided by the coverage of a gallon; primer is one coat of the same.
Worked example: a 40 × 30 ft one-story house with two 6 ft high gable ends and 150 ft² of openings has 1,290 ft² to paint and needs 7.4 gallons for two coats at 350 ft² a gallon, plus 3.7 gallons if you prime the whole house, and 7 tubes of caulk.
Exterior paint for common houses (two coats, 350 ft² a gallon)
Two gable ends 6 ft high, 9 ft stories, 150 ft² of openings (250 ft² for two stories).
| House | Surface to paint | Paint for two coats |
|---|---|---|
| 24 × 30 ft, 1 story | 1,002 ft² | 5.7 gal |
| 30 × 40 ft, 1 story | 1,350 ft² | 7.7 gal |
| 40 × 50 ft, 1 story | 1,770 ft² | 10.1 gal |
| 24 × 36 ft, 2 stories | 2,126 ft² | 12.1 gal |
| 30 × 40 ft, 2 stories | 2,510 ft² | 14.3 gal |
Tips before you buy
- Preparation decides how long a paint job lasts: wash, scrape, sand, repair rot, caulk gaps and prime bare spots.
- Replace badly rotted boards instead of filling them, and let wood dry fully before you prime.
- Buy the paint from one batch and mix the pails together (boxing), so that the color is the same around the house.
- Paint from the top of each wall down, keeping a wet edge, and do the trim and doors last.
- A sprayer is fast but wastes more paint and needs careful masking. Back-roll sprayed paint for a better bond.
Tools & materials for this project
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Frequently asked questions
How much paint do I need for a 40x30 house?
About 7.4 gallons for two coats on a one-story house with two gable ends and 150 ft² of windows and doors. Rough siding or stucco needs more.
How many coats of paint does the outside of a house need?
Two coats of a good exterior paint over a sound, clean surface, or one coat over primer on bare or patched areas plus a finish coat. Check the can.
Do I need to prime exterior siding?
Bare wood, patches and stains need primer. A coat of primer over this whole house is about 3.7 gallons, which is why spot-priming only the bare areas saves money.
How much paint for a two-story house?
A 24 × 36 ft two-story house with 250 ft² of openings needs about 12.1 gallons for two coats.
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Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.