Painting the outside of a house
House exterior is the mode the paint calculator opens in here. Type how long and how wide the footprint is, the wall height from the ground (or the top of the plinth you won’t paint) up to the eaves, and how many gable ends the roof has. Doors and windows come off as usual: the house starts with two doors and ten windows, so set them to yours. A house with a garage or an extension is easiest as a second building with its own footprint, or as one L-shaped footprint if the walls are the same height.
The wall area is the perimeter times the height, plus half the width times the gable height for each gable. A dormer or a bay adds a little wall that a footprint doesn’t show, so add a small extra building for it or round up.
Why exterior paint covers less
Outside walls are rougher and more porous than plaster, and coverage figures reflect it. Sherwin-Williams’ data sheet for Duration Exterior gives 250 to 300 sq ft per gallon. Dulux Trade’s data sheet for Weathershield Smooth Masonry Paint says the spreading rate “will vary considerably according to the roughness and porosity of the surface”: up to 16 m² per litre on smooth render, 4 to 6 m² per litre on pebbledash. On a textured surface use the maker’s lowest figure, and check the coverage after the first few square metres.
Before you order
Below, two tables list what common house sizes take. Tick the can sizes your supplier has, and the calculator shows how many pails or tins to order and how much will be left. A primer counts as a single coat on the whole wall at the primer’s rate; tick Primer first if the data sheet asks for one on bare masonry or wood.
Exterior paint for common house sizes
Two coats on a house with 17 ft (5.2 m) walls to the eaves, two gable ends 8 ft (2.5 m) high, two doors and ten windows, at the ends of each maker's coverage range.
| Footprint | Wall area | At 250 sq ft/gal | At 300 sq ft/gal |
|---|---|---|---|
| 24 × 32 ft | 1,940 sq ft | 15.5 gal | 12.9 gal |
| 26 × 34 ft | 2,092 sq ft | 16.7 gal | 13.9 gal |
| 28 × 40 ft | 2,380 sq ft | 19.0 gal | 15.9 gal |
| 30 × 50 ft | 2,804 sq ft | 22.4 gal | 18.7 gal |
| Footprint | Wall area | Pebbledash, 4 m²/L | Smooth render, 16 m²/L |
|---|---|---|---|
| 7 × 9 m | 166 m² | 83 L | 21 L |
| 8 × 10 m | 190 m² | 95 L | 24 L |
| 9 × 12 m | 223 m² | 112 L | 28 L |
| 10 × 14 m | 257 m² | 129 L | 32 L |
Sources, checked September 2026: Sherwin-Williams, Duration Exterior Acrylic Satin data sheet (250–300 sq ft per gallon); Dulux Trade, Weathershield Smooth Masonry Paint data sheet (up to 16 m² per litre on smooth render, 4–6 on pebbledash).