Things you may need
A quick list for the aisle. You may already own half of it.
- Paint
- Primer if needed
- Rollers
- Brushes
- Painter's tape
- Drop cloth
- Paint tray
- Sandpaper
- Spackle
Paint Calculator
Estimate how many gallons of paint to buy based on room size, wall height, doors, windows, coats, coverage, waste, and price.
Before you buy Measure once more, check the product label, then use this as your shopping-list number.
Enter your project details
Use the defaults for a quick estimate, or adjust the advanced fields to match the product you plan to buy.
How the estimate works
The calculator uses your measurements plus ordinary unit conversions. Editable fields handle the parts that change by product: waste, coverage, bag yield, box coverage, or material density.
The buy recommendation rounds up because stores do not sell half gallons, partial boxes, or a fraction of a bag.
Beginner notes
- Buy slightly more than the exact estimate for touch-ups.
- Dark color changes and textured walls may need extra paint.
- Check the coverage number on the paint can before buying.
- Primer can change how much finish paint you need.
Planning estimate only
Actual material needs change with product, installation method, surface condition, layout, waste, and local requirements. For structural, permit, drainage, electrical, plumbing, or load-bearing work, get qualified local guidance.
Questions people usually ask
How much does one gallon of paint cover?
Many interior paints cover about 250 to 400 square feet per gallon. This calculator uses 350 square feet as a default, but you can adjust it.
Should I include two coats?
For most interior repainting projects, two coats is a practical planning default.
Do doors and windows matter?
Yes. The calculator subtracts a default estimate for doors and windows so the paintable wall area is more realistic.
Helpful next reads
Painting
How to measure a room for paint
A plain way to measure walls, subtract doors and windows, and avoid buying the wrong amount of paint.
Accuracy
How accurate are these calculators?
Where estimates work, where they fail, and when to check the product label instead.
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