Every room has one door and one window. There's a table for 8 ft walls and one for 9 ft walls. The first column is the walls only. The second adds the ceiling in the same paint.
8 ft walls
| Room | Walls only | Walls + ceiling |
|---|---|---|
| 10 × 10 ft | 2 | 3 |
| 10 × 12 ft | 2 | 3 |
| 12 × 12 ft | 3 | 3 |
| 12 × 14 ft | 3 | 4 |
| 14 × 16 ft | 3 | 4 |
| 16 × 20 ft | 4 | 5 |
9 ft walls
| Room | Walls only | Walls + ceiling |
|---|---|---|
| 10 × 10 ft | 2 | 3 |
| 10 × 12 ft | 3 | 3 |
| 12 × 12 ft | 3 | 4 |
| 12 × 14 ft | 3 | 4 |
| 14 × 16 ft | 3 | 5 |
| 16 × 20 ft | 4 | 6 |
How this is worked out
Wall area is the distance around the room times the wall height. We take off the door, 3 ft by 6 ft 8 in, and the window, 3 ft by 4 ft. The ceiling is length times width.
A gallon covers 350 sq ft, which is what Handyman Calc assumes. Two coats means twice the area. We divide and round up to whole gallons.
There's no waste added, as in the app. Paint isn't cut and thrown away the way drywall is.
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The chart is on one page in the printable PDF, US Letter size.
More charts: how many bags of concrete a slab takes, how many sheets of drywall a room takes, a fraction to decimal chart for inches, how much mulch a bed takes, a roof pitch chart, how many steps a rise takes, the diagonal that squares a frame and board feet for common lumber.
To work out your own sizes, there's a material estimator spreadsheet, and more on the Handyman Calc page.