Paint Calculator – How Much Paint Do You Really Need?

No sign-up needed. Free paint calculator with metric & imperial units. Get accurate gallon estimates for walls, ceilings, and trim. Start calculating now.

Why This Paint Calculator Exists

I've been there. You're staring at paint swatches, trying to guess how many gallons to buy. Buy too little and you're making emergency trips to the store. Buy too much and you've wasted $50 on paint that'll sit in your garage for years. Most paint calculators force you to create an account or only work in feet. This one doesn't. You get your number in seconds. Metric or imperial. Your choice.

Typical Coverage Rates

Here's what major brands like Sherwin-Williams and Behr claim for their interior latex paints. These numbers are consistent across the industry. Use them to double-check our calculator.

How Much Paint for a Standard Room?

A typical US bedroom is 12x12 feet with 8-foot ceilings. That's four walls. Total wall area for one coat? About 384 square feet. For a single coat of interior latex, you'll need roughly 1.1 gallons. Most rooms need two coats. So plan on 2.2 gallons. Plus primer if the walls are bare or dark. That adds another 1.1 gallons. Total: about 3.3 gallons for primer plus two coats. In my experience, always round up. Buy 4 gallons. You'll use most of it, and leftover paint is great for touch-ups.

What About Cost?

Paint prices vary wildly. A gallon of interior latex runs $25 to $70. Typical price is around $40. Primer is cheaper: $20 to $50, typical around $30. For that 12x12 room with two coats of paint and one coat of primer, you're looking at roughly $110 to $160. Honestly, this won't work if you're using high-end designer paints that cost $100+ per gallon. But for standard Behr or Valspar? Those numbers hold.

When to Ignore the Calculator

Our paint calculator works great for smooth or lightly textured walls. If you've got heavy orange peel, knockdown texture, or brick, add 20% to the estimate. Textured surfaces eat paint. Also, if you're painting over a dark color with a light one, plan on three coats. The calculator assumes two coats for a typical color change. Caveat: dark red to white? You'll need more.

PaintWise Pick•Our Recommendation

Behr Premium Plus Ultra Interior Paint & Primer

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Frequently Asked Questions

How many gallons of paint do I need for a 12x12 room?: About 2.2 gallons for two coats of interior latex on the walls. Add 1.1 gallons if you're also priming.
Does this paint calculator work in metric units?: Yes. Switch to meters in the tool. Coverage rates are converted automatically.
Do I need to sign up to see my results?: No. Enter your dimensions, get your estimate instantly. No account required.
What if my room has lots of windows and doors?: Our calculator subtracts standard window and door area automatically. For unusual layouts, measure the wall area manually and subtract openings.
Can I use this for exterior paint?: This calculator is designed for interior walls. Exterior surfaces have different coverage rates due to texture and material.
Why do I need primer?: Primer seals bare drywall, covers stains, and helps paint adhere. It also reduces the number of paint coats needed. Skip it only if you're painting over a similar color.