Paint Calculator
Find out exactly how much paint you need for your room. Avoid buying too much or running out halfway through the job.
Gallons Needed
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Total Wall Area (sq ft)
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Paintable Area (sq ft)
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Door Area (sq ft)
0
Window Area (sq ft)
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Calculations assume a standard door is 21 sq ft and a standard window is 15 sq ft.
Paint calculator by square footage
To estimate paint from square footage, multiply paintable wall area by the number of coats and divide by the coverage listed on the can. This calculator uses room dimensions and subtracts standard door and window areas before estimating gallons.
For a room with 301 square feet of paintable wall area, two coats require 602 square feet of coverage. At 350 square feet per gallon, that is 1.72 gallons, so the calculator rounds up to 2 gallons.
How to Calculate Paint Needed
- Calculate Gross Wall Area: (2 × Length × Height) + (2 × Width × Height)
- Subtract Doors & Windows: Subtract 21 sq ft for each door and 15 sq ft for each window.
- Multiply by Coats: Multiply the paintable area by the number of coats.
- Calculate Gallons: Divide total needed area by the coverage per gallon (usually 350-400 sq ft). Round up to nearest whole gallon.
Example Calculation
For a 12' × 10' room with 8' ceilings, 1 door, and 2 windows, applying 2 coats:
- Gross Wall Area: (2 × 12 × 8) + (2 × 10 × 8) = 192 + 160 = 352 sq ft
- Door & Window Area: (1 × 21) + (2 × 15) = 21 + 30 = 51 sq ft
- Paintable Area: 352 - 51 = 301 sq ft
- Total Coverage (2 coats): 301 × 2 = 602 sq ft
- Gallons Needed: 602 / 350 = 1.72 gallons → 2 Gallons
Frequently Asked Questions
How much paint do I need per square foot?
Divide the paintable square footage by the coverage per gallon, after accounting for the number of coats. For example, 700 square feet of paintable wall area with two coats needs 1,400 square feet of coverage; at 350 square feet per gallon, that is 4 gallons.
Can I estimate paint cost with this calculator?
Yes. Enter the price per gallon to estimate the material cost for the whole gallons the calculator says you need. Labor, primer, trim, tools, and other project costs are not included.
how much paint do i need?
To estimate paint, calculate the wall area, subtract doors and windows, multiply by the number of coats, and divide by the coverage listed on the paint can. Round up to the next whole gallon.
How much does a gallon of paint cover?
A standard gallon of interior paint covers about 350 to 400 square feet for a single coat. Primer may cover less, around 200-300 square feet.
How many coats of paint do I need?
For most interior walls, two coats of paint are recommended for full coverage and color accuracy. If painting over a dark color with a lighter one, you may need a coat of primer plus two coats.
Should I subtract doors and windows?
Yes, subtracting the area of doors (approx 21 sq ft) and windows (approx 15 sq ft) ensures you do not buy unnecessary paint.
How do I calculate paint for multiple rooms?
Calculate the total paintable area for each room separately, add them together, multiply by the number of coats, and then divide by your coverage per gallon.