Material calculator
Paint Calculator
Estimate paint gallons and primer for one or more rooms with doors, windows, coats, and ceilings.
These results are planning estimates only. Verify product labels, site conditions, local requirements, and professional guidance before buying or building.
Calculator inputs
Adjust the typical defaults below. Results update automatically.
Results
Review quantities, warnings, and the shopping list before buying.
Paintable wall area
302sq ft
Ceiling area
0sq ft
Exact paint
1.73gal
Paint to buy
2gal
Primer to buy
0gal
Material list
- 2 gal Interior paint2 coats included
- 0 gal PrimerNot selected
- Verify separately Tape, rollers, brushes, traysNot estimated by this calculator
Breakdown
| item | wallAreaSqFt | openingsSqFt | paintableWallSqFt | ceilingSqFt |
|---|---|---|---|---|
| Room 1 | 352 | 50 | 302 | 0 |
How to use
- Enter room dimensions, openings, and coat counts.
- Choose whether to include the ceiling and primer.
- Review exact gallons and rounded gallons to buy.
Input guide
- Default deductions use 20 sq ft per door and 15 sq ft per window.
- Paint coverage should come from the can label when possible.
- Primer coverage can differ from paint coverage.
Common mistakes
- Forgetting the second coat.
- Not adjusting coverage for rough, patched, or dark surfaces.
- Counting ceiling paint with wall paint when using different products.
Assumptions and limitations
- Actual coverage depends on surface, color change, paint type, and application method.
- Door and window deductions are estimates.
- No advice is provided on lead paint, surface hazards, or ventilation.
Formula
- Wall area = 2 x (length + width) x height.
- Paintable wall area = wall area - door, window, and custom opening area.
- Paint area = paintable wall area x coats + ceiling area x ceiling coats.
- Gallons to buy = paint area / paint coverage, rounded up.
Example
A 12 ft x 10 ft x 8 ft room has 352 sq ft of wall area. After one door and two windows, two coats need 604 sq ft of coverage, or 2 gallons at 350 sq ft per gallon.
FAQ
Why does the calculator round gallons up?
Paint is typically purchased in fixed container sizes, and a small shortage can cause color or finish inconsistencies.
Do I always need primer?
No. Primer depends on surface condition, stains, bare material, and color change. The calculator only estimates quantity if you choose primer.