PAINTING
How to Calculate Paint Quantity
Contractor method for calculating paint quantity: area, coats and coverage.
Paint runs out on the coats and the coverage. The area is easy math; the number of coats and the paint's real coverage determine how many gallons you need.
THE SHORT ANSWER
How do you calculate paint quantity?
Measure area, multiply by coats and divide by coverage. 500 sq ft at 2 coats over 350 sq ft/gal needs 2.86 gallons, so buy at least 3 gallons before adding any job-specific waste allowance.
Measure the paintable area
Measure the surface to paint in sq ft, not the floor area. Count all the walls and subtract openings. Note the surface texture — rough surfaces eat more paint.
- Measure walls, not floor
- Subtract windows and doors
- Note the surface texture
- Count ceilings and trim separately
Set the coats
Two coats are the standard for even coverage. Dark colors over light, or bare drywall, may need three. Each coat multiplies the area.
Apply the coverage
Interior paint covers ~350 sq ft/gal per coat. Divide the total area by the coverage. Use the Paint Quantity Calculator to size the material, then add 10-15% for waste.
Check against the job
Your quantity should cover the whole job with a little spare. Running out mid-job costs more than buying an extra gallon.