Honest math
Everything is shown — total area, deductions, coats. You can verify it yourself.
Free • No signup • Instant
How much paint do I need?
Enter your room size, doors, and windows. CoverCalc tells you exactly how many gallons to buy — so you don’t overpay or run out mid-coat.
- Used by DIYers & pros
- Math you can verify
- Mobile-friendly
Paint calculator
Measure your walls in feet. Defaults match a typical room — change anything.
You need
0 gallons
0 sq ft of paintable wall · 0 sq ft total wall area
Round up — extra paint covers touch-ups for years.
around them to enable. -->Shop 3 gallons of interior paint:
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How CoverCalc works
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1
Measure your walls
Length, width, ceiling height. A tape measure is enough.
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2
Subtract openings
We deduct 21 sq ft per door and 15 sq ft per window automatically.
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3
Choose coats
Two coats is standard. One if you’re refreshing the same color.
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4
Buy the right amount
We round up to whole gallons so you don’t run out mid-wall.
Built for one job, done well
No popups, no signup
You came for an answer. You get an answer. That’s the whole product.
Works on your phone
Use it standing in the paint aisle. It’s fast and the buttons are big.
Smart defaults
Pre-filled with realistic values so you can get an estimate in two seconds.
Paint guides
Quick reads that answer the questions every painter Googles.
How much paint for a room?
Standard rooms by size — bedroom, living room, bathroom.
How many coats of paint?
When one coat works, when you need two, and when three.
Paint coverage per gallon
What the cans say vs. what you actually get.
Exterior paint calculator
Siding, trim, and how weather changes coverage.
Frequently asked questions
How much paint do I need for one room?
A standard 12x12 ft room with 8 ft ceilings needs about 1.5 gallons of paint for one coat on the walls. Most projects need two coats, so plan for around 3 gallons. Use the calculator for an exact number.
How many square feet does one gallon of paint cover?
One gallon of interior wall paint covers roughly 350 sq ft on a smooth, primed surface. Rough or unprimed surfaces cover less — sometimes 250 sq ft per gallon.
Do I need primer?
Use primer when painting over bare drywall, stained surfaces, dark colors, or glossy finishes. Skip primer when repainting a similar color over existing latex paint in good condition.
Should I subtract doors and windows?
Yes. The calculator subtracts a standard door (21 sq ft) and window (15 sq ft) per count. This keeps your gallon estimate from running over.
Does the calculator include the ceiling?
No — walls only by default. A separate ceiling calculator is on the roadmap.