Paint calculator: how much paint do I need?
Enter the room size, doors, windows and coats. The calculator takes the openings off the wall area, adds the ceiling if you paint it, and divides by the coverage on the can, rounding up to whole gallons (or litres).
Price this job as an estimate in Quotesprig (free)
Common sizes, worked out
Wall paint for one room, 2 coats, 1 door, 2 windows, 8 ft walls, ceiling not painted. Every number below comes from the same calculator code as the tool above.
| Job | Wall area to paint | Wall paint | Labour |
|---|---|---|---|
| 10 × 10 ft room | 269 sq ft | 2 gal | 3.6 hr |
| 12 × 12 ft room | 333 sq ft | 2 gal | 4.4 hr |
| 14 × 12 ft room | 365 sq ft | 3 gal | 4.9 hr |
| 16 × 14 ft room | 429 sq ft | 3 gal | 5.7 hr |
| 20 × 15 ft room | 509 sq ft | 3 gal | 6.8 hr |
Assumptions you can change
Starting values: area per door 21 sq ft, area per window 15 sq ft, paint coverage 350 sq ft/gal, primer coverage 300 sq ft/gal, your production rate 150 sq ft/hr. They are typical starting points, not rules: use the numbers on your product labels and your own production rate.
FAQ
How much paint do I need for a 12x12 room?
For a 12 × 12 ft room (wall paint for one room, 2 coats, 1 door, 2 windows, 8 ft walls, ceiling not painted): wall area to paint 333 sq ft; ceiling area 0 sq ft; wall paint 2 gal. Change any input above for your own job.
Does the calculator include the ceiling?
Yes, if you set "Paint the ceiling" to Yes: it adds length × width per room and works out ceiling paint as its own line.
What coverage should I use?
Use the number printed on your paint can. The calculator starts at 350 sq ft per gallon (8.6 m² per litre), a common figure for interior paint on smooth walls; rough or porous surfaces need more paint.
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