Paint calculator
Paint Coverage Calculator
Convert known wall area, coats, coverage rate, and waste percentage into estimated gallons of paint.
When to use this calculator
Use this calculator when you already know the surface area and want a direct paint quantity estimate. It is ideal for multi-room jobs, exterior sections, accent walls, and projects where you measured area separately.
Coverage varies by product and surface. Always use the can label for the paint you actually plan to buy.
Formula used
Gallons = wall area × coats × (1 + waste percentage ÷ 100) ÷ coverage per gallon.
The formula is intentionally simple so it can be used for quick planning. Real bills, quotes, and installation costs can include fixed fees, taxes, tiers, labor, product limits, and site-specific conditions that a calculator cannot see.
Input guide
| Input | How to use it |
|---|---|
| Wall area | Total paintable surface area in square feet. |
| Coats | The number of planned coats. |
| Coverage | Paint coverage per gallon from the product label. |
| Waste | Extra percentage for touch-ups, texture, roller loss, and mistakes. |
Examples
Known area
500 sq ft, two coats, 350 sq ft/gallon, and 10% waste needs about 3.14 gallons.
Rough wall
A rough or patched wall may need a higher waste margin or primer.
How to get a more accurate result
- Use exact product coverage.
- Separate primer from finish paint.
- Increase waste for rough or absorbent surfaces.
Common mistakes to avoid
- Using one-coat coverage when planning two coats.
- Forgetting primer.
- Using total room area instead of paintable surface area.
Quick checklist before relying on the result
- Measure paintable area.
- Confirm coats.
- Read coverage label.
- Add waste margin.
FAQ
Can I use this for exterior paint?
Yes, but exterior surfaces often need more allowance for texture and weathering.
Should primer be included?
Calculate primer separately because coverage can differ.
Do gallons round up?
In real buying, round up to available can sizes and keep touch-up paint.