Home & Renovation
Paint Calculator
Calculate gallons of paint needed for any room based on dimensions.
Running out of paint mid-wall is frustrating. Buying too much wastes money. This calculator uses wall area, number of coats, and standard coverage rates to give you an accurate quantity.
Paint Needed
3 Gallons
- net Sqft
- 392 sq ft to paint
- with Waste
- 3 gallons (with 10% waste)
- quarts
- 9 quarts
Formula and method
Gallons = (Net Square Footage / 350) × Coats
Standard coverage rate of 350 sq ft per gallon for average interior paint. Premium paints and dark colors may cover less. Buy an extra 10% for touch-ups and waste.
Worked examples
Standard bedroom
- Wall Width (ft):
- 12
- Wall Height (ft):
- 9
- Number of Walls:
- 4
- Number of Coats:
- 2
- Number of Windows/Doors:
- 2
Paint Needed: 3 Gallons
Open-plan living room
- Wall Width (ft):
- 20
- Wall Height (ft):
- 10
- Number of Walls:
- 4
- Number of Coats:
- 2
- Number of Windows/Doors:
- 4
Paint Needed: 5 Gallons
Assumptions and limits
- 350 sq ft/gallon standard coverage
- Rectangular walls only
- 20 sq ft per door or window
This tool provides an educational estimate. Rules, rates and personal circumstances can change the answer. Review the assumptions before relying on a result. Report a correction.
Common mistakes to avoid
- Not subtracting doors and windows — adds 10-15% waste on most rooms.
- Using a single-coat coverage rate for two-coat jobs — double the quantity needed.
- Forgetting ceiling paint — ceilings typically need separate flat paint.
Frequently asked questions
How much does paint coverage vary by type?
Standard latex paint: 350 sq ft/gallon. High-build paint: 200-250 sq ft/gallon. Stains: 150-300 sq ft/gallon. Primer: 200-400 sq ft/gallon. Always check the manufacturer's spec sheet.
Should I buy extra?
Always buy 10% extra to account for drips, touch-ups, and inconsistent application. Store leftover paint sealed tightly — it keeps for years for touch-ups.
Related calculators
Square Footage Calculator
Calculate square footage, perimeter, and square meters for any room.
Flooring Calculator
Calculate boxes and cost of hardwood, laminate, or tile flooring.
Drywall Calculator
Calculate sheets of drywall needed for a renovation project.
Deck Cost Estimator
Estimate material and labor cost to build a deck.