Paint Calculator
Find how many gallons of paint you need for walls and ceilings, including coats and waste.
Paint needed
1.75 gallons
314 sq ft net surface × 2 coat(s)
- Exact gallons
- 1.67
- Wall area (gross)
- 384 sq ft
- Openings subtracted
- 70 sq ft
- Estimated cost
- $73.50
Door openings assumed ~20 sq ft and windows ~15 sq ft each. Adjust counts if your openings differ a lot.
How this calculator works
Paint coverage is typically 350–400 square feet per gallon on smooth sealed surfaces. Rough or porous walls cover less.
Multiply wall area by the number of coats, divide by coverage, and round up to the next quart or gallon size you’ll actually buy.
gallons = (area × coats) ÷ coverage per gallon
- One gallon often covers ~350–400 sq ft
- Dark color changes may need extra coats
- Primer is separate - don’t skip it on new drywall
Frequently asked questions
How much paint do I need for a room?
Add up wall (and ceiling) square footage, multiply by coats, and divide by 350–400. A 12×12 room with 8-ft ceilings has about 384 sq ft of walls - roughly 2 gallons for two coats.
How many square feet does a gallon of paint cover?
Most interior latex paints claim 350–400 sq ft per gallon. Textured walls, bare drywall, and deep colors reduce real-world coverage.
Should I buy extra paint?
Yes - keep a quart for touch-ups. Batch numbers vary, so leftover from the same purchase matches better later.
Related calculators
Keep planning your project with these tools, or browse the Interior Finish category.