Paint Amount Calculator
Estimate how much paint you need for your project and the total cost based on coverage and price per gallon.
Room Dimensions
Results
Enter dimensions to estimate paint needs.
How to Estimate Paint for a Room
One gallon of paint typically covers 350–400 square feet of wall space with a single coat on a smooth, previously painted surface. Rough, porous, or unpainted surfaces absorb more paint and may require a primer plus additional coats. Most interior painting projects use two coats — a first coat to establish the base color and a second coat for even coverage and durability.
To estimate total square footage, measure the perimeter of the room (the total length of all walls) and multiply by the ceiling height. Then subtract the area of doors (roughly 20 sq ft each) and windows (roughly 15 sq ft each) to avoid significantly over-buying.
Paint Coverage Reference
| Paint Type | Coverage per Gallon |
|---|---|
| Standard interior latex | 350 – 400 sq ft |
| Primer / first coat on bare drywall | 250 – 300 sq ft |
| Exterior paint | 250 – 350 sq ft |
| High-gloss enamel | 300 – 350 sq ft |
How to Use This Calculator
- Enter the room dimensions — length, width, and ceiling height in feet.
- Enter the number of doors and windows in the room.
- Select the number of coats you plan to apply.
- Click Calculate to see the total square footage to paint and estimated gallons needed.
Frequently Asked Questions
Do I need to include the ceiling in my paint estimate?
The ceiling is separate from the walls and typically requires its own paint (often a flat white ceiling paint). To estimate ceiling paint, simply multiply the room's length by its width to get the square footage. A standard 12×15 ft room ceiling is 180 sq ft — about half a gallon per coat.
How many coats of paint do I need?
Most interior repaints require two coats for even coverage. If you're making a dramatic color change (from dark to light or vice versa), you may need three coats or a tinted primer as the first coat. New drywall typically needs a primer plus two finish coats.
Should I buy a little extra paint?
Yes — always buy at least 10% more than your estimate. Keep the leftover paint in a properly sealed can for touch-ups, which are inevitable as walls take minor dings and scuffs over time. Storing a small amount of the exact color saves a trip to the paint store and ensures a perfect match later.