Paint Calculator
Enter your room dimensions or total square footage to find exactly how many gallons of paint you need.
Calculation method
Each subtracts ~20 sq ft
Each subtracts ~15 sq ft
Paintable surface area
Results
Gallons
—
gallons needed
Quarts
—
if buying quarts
Sq Ft to Paint
—
sq ft (all coats)
How to Calculate Paint Coverage
Standard interior paint covers approximately 350–400 square feet per gallon on smooth surfaces. This calculator uses 350 sq ft per gallon as a conservative estimate that accounts for slight texture and normal application variance.
For a room, calculate the total wall area (perimeter × height), subtract doors and windows, then multiply by the number of coats. Divide the total square footage by 350 to get gallons.
Coverage by Paint Type
| Paint Type | Coverage per Gallon | Notes |
|---|---|---|
| Interior flat / matte | 350–400 sq ft | Hides imperfections well |
| Interior eggshell / satin | 350–400 sq ft | Most common for walls |
| Interior semi-gloss | 300–350 sq ft | Trim, kitchens, baths |
| Exterior paint | 250–350 sq ft | Rougher surfaces reduce coverage |
| Primer | 200–300 sq ft | New drywall, dark colors |
Frequently Asked Questions
- How many coats of paint do I need?
- Two coats is standard for most interior projects. One coat may work for touch-ups or same-color repaints. Going from dark to light, or painting new drywall, typically requires a primer coat plus two finish coats.
- Should I buy extra paint?
- Yes — always buy at least 10% more than calculated. Keep a small amount in a sealed container for future touch-ups. Paint batches can vary slightly in color, so matching later is difficult.
- Is it better to buy gallons or quarts?
- Gallons are significantly cheaper per square foot. Only buy quarts if you need less than half a gallon, or for accent colors used in small areas. For anything over 150 sq ft, buy gallons.