What is the Paint Calculator?
Estimate how many gallons of paint you need for a room. Order the right amount the first time. These construction and DIY calculators estimate materials for common home projects and include sensible waste allowances.
How to use the Paint Calculator
- Enter your room length, your room width, your wall height, your doors and the remaining fields.
- Results update automatically as you type; you can also press Calculate.
- Read the output: paint needed, gallons to buy, paintable wall area.
- Use the 📊 chart to see the result visually, then copy or share it.
Formula and method
Worked example
With room length = 14 ft, room width = 12 ft, wall height = 8 ft, doors = 1, windows = 2, the Paint Calculator returns paint needed: 2.09 gal; gallons to buy: 3; paintable wall area: 365 ft².
Tips for better results
- Add 5–15% for waste, cuts and breakage depending on the material.
- Measure twice and round up when buying — returns are easier than second trips.
- Coverage figures vary by product, so check the label or spec sheet.
⚠️ Material estimates are approximate. Follow local building codes and manufacturer instructions.
Frequently asked questions
What does the Paint Calculator do?
Estimate how many gallons of paint you need for a room.
How is it calculated?
The Paint Calculator uses this method: Area = perimeter × height − doors (21 ft²) − windows (15 ft²); Gallons = Area × coats ÷ coverage.
Can you show an example?
With room length = 14 ft, room width = 12 ft, wall height = 8 ft, doors = 1, windows = 2, the Paint Calculator returns paint needed: 2.09 gal; gallons to buy: 3; paintable wall area: 365 ft².
Is the Paint Calculator accurate?
It uses standard published formulas and is tested against known values, but results are estimates for guidance. Material estimates are approximate. Follow local building codes and manufacturer instructions.
Is this tool free and private?
Yes — the Paint Calculator is completely free with no sign-up, and it runs entirely in your browser, so the values you enter are never uploaded to our servers.
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