Paint for a 16 × 20 ft room
This is a very large living room or open-plan space. With 8 ft ceilings the four walls have 576 ft² of surface, and after deducting one door (21 ft²) and two windows (30 ft²) there are 525 ft² to paint. The ceiling is 320 ft².
How the number of coats changes it
| Coats | Wall gallons | Buy for walls | Ceiling gallons | Buy for ceiling |
|---|---|---|---|---|
| 1 coat | 1.50 | 1 gallon + 2 quarts | 0.91 | 1 gallon |
| 2 coats | 3.00 | 3 gallons | 1.83 | 2 gallons |
| 3 coats | 4.50 | 4 gallons + 2 quarts | 2.74 | 2 gallons + 3 quarts |
If your ceilings are taller
| Ceiling height | Wall area | Gallons (2 coats) | Buy |
|---|---|---|---|
| 8 ft ceilings | 576 ft² | 3.00 | 3 gallons |
| 9 ft ceilings | 648 ft² | 3.41 | 3 gallons + 2 quarts |
| 10 ft ceilings | 720 ft² | 3.82 | 4 gallons |
If your walls are rough or your paint covers less
The label on your can gives its coverage. Rough or textured walls and dark colors cover less, so the amounts go up:
| Coverage | Gallons (2 coats) | Buy |
|---|---|---|
| 250 ft² per gallon | 4.20 | 4 gallons + 1 quart |
| 300 ft² per gallon | 3.50 | 3 gallons + 2 quarts |
| 350 ft² per gallon | 3.00 | 3 gallons |
| 400 ft² per gallon | 2.63 | 2 gallons + 3 quarts |
Want to change anything else? The calculator above is the full Paint Calculator: edit any number and the results update instantly.
Tools & materials for this project
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Frequently asked questions
How many gallons of paint do I need for a 16x20 room?
With 8 ft ceilings, one door, two windows and two coats at 350 ft² per gallon, the walls need 3.00 gallons, so buy 3 gallons. If you also paint the ceiling, add 1.83 gallons (2 gallons).
How much paint for the walls and ceiling of a 16x20 room?
Walls and ceiling together need about 4.83 gallons for two coats. That is 5 gallons if you use the same paint on both, though ceilings are usually painted with a separate flat ceiling paint.
How much primer do I need for a 16x20 room?
One coat of primer over the same walls is about 1.50 gallons (1 gallon + 2 quarts). Primer often covers a little less than paint on bare surfaces, so check the can.
Related sizes and guides
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.