How Much Paint for a 12x20 Room?
Paint needed
2.5 gallons
A 12 by 20 room with eight foot walls, two doors, three windows, two coats.
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How that number is worked out
These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.
- Room perimeter, add all walls64 ft
- Wall height8 ft
- Doors2
- Windows3
- Coats2
- Coverage per gallon350 sq ft
Paint needed2.5 gallons
| Gross wall area | 512 sq ft |
|---|---|
| Less doors and windows | -87 sq ft |
| Net wall area | 425 sq ft |
| Area over 2 coats | 850 sq ft |
| Gallons, exact | 2.43 |
| Buy | 3 gallonsor 1 five gallon pail |
The material list this produces
| Paint, gallons | 3 |
|---|---|
| Primer, gallons (if bare or color change) | 2 |
| Painter's tape, rolls | 2 |
Coats compared
Coats is the input people get wrong, usually by hoping. Same room, one coat to three.
| Coats | Paint needed |
|---|---|
| 1 coat | 1.25 gallons |
| 2 coats | 2.5 gallons |
| 3 coats | 3.75 gallons |
What else matters here
Sixty four feet of perimeter, two doors and three windows: 425 square feet net and two and a half gallons over two coats. This is a living room, and living rooms are the rooms where wall finish shows most, because they have the most light coming in from the most directions.
That is an argument for buying the better paint here rather than everywhere. A twenty foot wall with three windows along it is raked by light all day, and every roller lap, every missed spot and every patch that was not primed will be visible from the sofa for years.
Work wet edge to wet edge on a wall that long. Cut in one wall, roll it immediately and finish it before moving on, rather than cutting in the whole room and rolling afterwards, because paint that has started to set will show where the next section joins it.
What this calculator assumes
- A door is taken as 21 sq ft and a window as 15 sq ft. Deducting them matters on a small room and barely moves a big one.
- 350 sq ft per gallon is the usual figure on a smooth primed wall. Bare drywall, textured walls and deep color changes all drink more, so drop it to 300 if any of those apply.
- Ceilings and trim are not included. Run the ceiling as its own area.
Questions people ask
How much paint for a 12x20 room?
About 2.43 gallons for two coats on eight foot walls with two doors and three windows, so two and a half gallons.
What is a wet edge and why does it matter?
It means rolling into paint that is still wet rather than onto paint that has begun to set. On a long wall in side light, a dry join shows as a visible band.
Is expensive paint worth it in a living room?
It is the room where it shows most, because of the light. Better paint covers in fewer coats and levels out lap marks, which is exactly what a long, well lit wall punishes.
The paint calculator takes any dimensions you like and hands back the same list.