Paint Calculator
Enter your room or wall size and local prices — empty prices count as zero
Paint Calculator: How Much Paint Do You Need?
A paint calculator works out how many gallons you need before you go to the store. Enter the length, width and height of a room, or type in a wall area you already know, then choose the number of coats and the coverage of your paint. This free paint calculator subtracts doors and windows, adds a small amount for touch-ups, rounds up to whole gallons and shows the cost of paint, primer, supplies and labor. You can include the ceiling and primer, and it works in feet or meters.
Quick answer: a 14 by 12 foot room with 8 foot walls, one door and two windows has about 366 sq ft of wall. Two coats with 10 percent extra need 2.30 gallons, so you buy 3 gallons, which comes to about $145 with the default prices.
How the Amount of Paint Is Calculated
The calculator finds the paintable wall area, then divides the paint needed for all coats by the coverage of one gallon.
The result is rounded up because paint is sold by the gallon. If you include the ceiling, its area is length × width.
Worked Example
For the room above, the wall area is 2 × (14 + 12) × 8 − 20 − 30 = 366 sq ft. Two coats with 10 percent extra give 366 × 2 × 1.10 ÷ 350 = 2.30 gallons.
| Item | Quantity | Cost |
|---|---|---|
| Wall paint, 2 coats | 3 gallons | $105 |
| Supplies | $40 | |
| Total | $145 |
If you also paint the ceiling (168 sq ft), it needs 1.06 gallons, so you would buy 2 more gallons of ceiling paint.
Paint Needed for Common Room Sizes
These figures assume 8 foot walls, one door, two windows, two coats, 10 percent extra and 350 sq ft per gallon. Ceilings are not included.
| Room (L × W × H) | Wall area (1 door, 2 windows) | Paint for 2 coats |
|---|---|---|
| 10 × 10 × 8 ft | 270 sq ft | 2 gal |
| 12 × 12 × 8 ft | 334 sq ft | 3 gal |
| 14 × 12 × 8 ft | 366 sq ft | 3 gal |
| 16 × 14 × 8 ft | 430 sq ft | 3 gal |
| 20 × 15 × 8 ft | 510 sq ft | 4 gal |
Paint Coverage by Surface
Coverage depends on the surface and the paint, so check the label on the can. Rough or porous surfaces drink more paint, which means you need more gallons. Change the coverage in the calculator to match your product.
| Surface | Typical coverage per gallon |
|---|---|
| Smooth, primed drywall | 350 to 400 sq ft |
| Previously painted walls | 350 to 400 sq ft |
| Textured walls or stucco | 250 to 300 sq ft |
| Bare drywall or wood (primer) | 200 to 300 sq ft |
| Brick or masonry | 150 to 250 sq ft |
Tips for Buying and Applying Paint
Buy all the paint for a room at the same time and mix the cans together so the color stays even. Clean walls, fill holes, sand lightly and tape edges before you begin. Primer is worth the cost on bare drywall, stains and big color changes. For other building jobs, the concrete calculator, roofing calculator and area calculator can help you plan materials.
Limits of This Calculator
The estimate assumes simple rectangular rooms and standard doors and windows. Vaulted ceilings, stairwells, trim, cabinets, exterior siding and very textured surfaces need extra measuring. Treat the result as a planning figure and keep a little paint in reserve.
Who Can Use This Calculator?
Homeowners and renters repainting a room, landlords preparing units, painters and contractors preparing quotes, and anyone comparing paint costs before a project.
How to Use This Paint Calculator
Enter the size
Type the length, width and height of the room and the number of doors and windows, or switch to Wall Area if you already know it. Choose feet or meters.
Choose coats and extra paint
Pick the number of coats and use the slider to add extra paint for touch-ups.
Add ceiling, primer and prices
Include the ceiling or primer if needed, then enter your local prices. Leave a price empty to count it as zero.
Read the estimate
See the gallons to buy, the amount needed and the total cost update as you type.