Materials planning tool
Paint Calculator
Subtract aggregate openings, account for coats and waste, then use your paint label's coverage to plan a conservative US container mix.
Estimate wall paint
Enter wall area, coatings, and the exact product-label coverage.
Use the coverage printed on the exact product label. The starting value is only an example.
Schematic only; aggregate openings are shown as an area deduction, not as door or window geometry.
Estimate calculated
Paint estimate: 1.6 gal before waste; 1.76 gal after waste; purchase 2 gal; 0.24 gal estimated leftover.
2 gal to purchase
- Paint needed before waste
- 1.6 gal
- Paint needed after waste
- 1.76 gal
- Purchased volume
- 2 gal
- Estimated leftover
- 0.24 gal
- 2 x 1-gal can
Input recap
- Method
- Room perimeter
- Perimeter
- 40 ft
- Height
- 8 ft
- Openings
- 40 sq ft
- Coats
- 2
- Waste
- 10%
- Label coverage
- 350 sq ft/gal
Assumptions
- Net wall area equals gross measured wall area minus the aggregate openings area.
- Paint before waste equals net area times coats divided by the exact product-label coverage; the waste allowance is then applied separately.
- The editable coverage rate must come from the label for the exact paint selected.
Calculation details
320 sq ft gross wall area
280 sq ft net paint area
280 sq ft x 2 coats = 560 sq ft of coverage before waste
560 sq ft ÷ 350 sq ft per gal = 1.6 gal before waste
1.6 gal x 1.1 waste factor = 1.76 gal after waste
2 gal purchased - 1.76 gal needed after waste = 0.24 gal estimated leftover
Before you buy
- Is the surface porous or heavily textured?
- Are you making a dramatic color change?
- Does the product call for a separate primer?
- Will spraying or another application method affect expected coverage?
Porosity, texture, dramatic color changes, primer, and application method can change actual use. Verify product coverage and available container sizes before buying. Estimated leftover is only the selected containers minus this plan's after-waste requirement; do not assume leftover can be reused across different products or surfaces.
Source and editorial defaults
Source example: a gallon typically covers about 350 to 400 square feet, while a quart covers 100 square feet. Product needs vary with application and surface conditions.
Editorial default: The 350 sq ft/gal value is an editable illustrative starting point within the sourced typical range, not a universal coverage claim.
Container planning: The fixed 5-gallon, 1-gallon, and 1-quart sizes are an editorial planning set; verify which sizes your chosen product and store actually offer.
Source check: July 10, 2026.
How the estimate works
Net area = gross wall area - openings. Paint before waste = net area x coats ÷ the editable product-label coverage. Paint after waste = that liquid volume x (1 + waste share). Container selection uses the least quarter-gallon increment that meets the after-waste result, then the fewest containers and sizes. Estimated leftover = purchased volume - after-waste required volume.
Worked coverage comparison
Paint coverage chart by wall area
Compare theoretical liquid volume for one or two coats across seven common net wall areas.
| Net wall area | Metric area | One coat | Two coats |
|---|---|---|---|
| 100 sq ft | 9.3 m² | 0.29 gal | 0.57 gal |
| 200 sq ft | 18.6 m² | 0.57 gal | 1.14 gal |
| 300 sq ft | 27.9 m² | 0.86 gal | 1.71 gal |
| 400 sq ft | 37.2 m² | 1.14 gal | 2.29 gal |
| 500 sq ft | 46.5 m² | 1.43 gal | 2.86 gal |
| 750 sq ft | 69.7 m² | 2.14 gal | 4.29 gal |
| 1,000 sq ft | 92.9 m² | 2.86 gal | 5.71 gal |
This worked comparison uses 350 sq ft per gallon and excludes waste, primer, surface texture, application loss, and color-change effects. Use the coverage printed on the exact product label.
Guidance checked 2026-07-10. See Source and editorial defaults for the sourced range and planning limits.
Guides for this calculation
Check the measurements, assumptions, and worked examples in the related guides. Return to Materials planning for the full decision sequence, or review the tool methodology for formulas and limits.