How much paint do I need for a room?
Measure the room, subtract openings, choose coats, and turn paintable area into whole gallons.
Short answer
Measure the room walls, subtract doors and windows, add the ceiling only when needed, then divide by the product coverage after accounting for coats.
For homeowners planning wall or ceiling paint for a room or a directly measured surface.
How to do it
Choose a mode
Use room mode for four wall dimensions, or direct-area mode when you already know the paintable wall area.
Measure openings
Enter repeated door and window area that will not receive the wall paint.
Set coats and coverage
Choose whether to include the ceiling, then use the product label coverage when available.
Check the purchase
Round up to whole gallons and plan primer, trim, cabinets, and touch-ups separately.
Formula
Room wall area is 2 × (length + width) × height. Subtract openings, optionally add the ceiling, then divide coats by coverage.
Illustrative example
A 12 × 10 room with 8 ft walls has 352 sq ft of gross walls. Subtract a 21 sq ft door and two 15 sq ft windows for 301 sq ft. Two coats at 350 sq ft per gallon need about 1.72 gallons, or 2 gallons to buy.
Common mistakes
- Forgetting wall height
- Painting openings in the area total
- Using coverage from a different surface or color change
Before you buy
Confirm coverage, primer needs, color change, sheen, and whether trim or cabinets need a separate product and quantity.
What this guide does not cover
This does not estimate primer, trim, cabinets, accent walls, labor, or the effect of unusual surface texture beyond the coverage input.
Use the calculator
Paint Calculator is the primary tool for this guide. You can also browse the other interior calculators.