How much paint do I need?
For a room, wall area is 2 x (length + width) x wall height. A 12 x 12 room with 8 ft walls, 2 coats, and 350 sq ft per gallon needs about 2.19 gallons before a separate buffer.
Coverage changes by surface
Porous drywall, patched areas, textured walls, dark color changes, exterior surfaces, and rough wood can reduce real coverage per gallon.
Estimate rooms separately
Separate rooms, ceilings, trim, doors, cabinets, decks, and accent walls when coats, color, surface type, or coverage differs.
Paint room example estimates
Examples use 2 coats and 350 sq ft per gallon before subtracting openings.
| Room | Wall area for 2 coats | Estimated gallons |
|---|---|---|
| 10 ft x 12 ft room | 704 sq ft | 2.01 gallons |
| 12 ft x 12 ft room | 768 sq ft | 2.19 gallons |
| 12 ft x 16 ft room | 896 sq ft | 2.56 gallons |
| 15 ft x 20 ft room | 1,260 sq ft | 3.60 gallons |
Before you calculate
- Measure paintable surface area rather than relying only on floor area.
- Separate walls, ceilings, trim, decks, cabinets, and exterior surfaces when products or coats differ.
- Use the actual product coverage from the label.
Common mistakes
- Forgetting coat count, primer, texture, color changes, and surface porosity.
- Combining trim, ceilings, doors, and walls in one estimate.
- Ignoring pattern repeat for wallpaper or absorption for stain.
Formula
gallons = ((2 * (length + width) * wallHeight) * coats) / coveragePerGallon
Assumptions
- Coverage changes with product, surface texture, primer, color change, coats, and surface condition.
- Openings, trim, ceilings, cabinets, repairs, masking, and separate coatings should be estimated separately when needed.
- Use the selected product label and a realistic coat count before buying paint.
Example
Estimated kids room paint needed: 2.01 gallons
How to use this calculator
- Enter room length in ft.
- Enter room width in ft.
- Enter wall height in ft.
- Enter coats in count.
- Enter coverage per gallon in sq ft.
- Review the live estimate and compare it with the example result.
- Check the formula, assumptions, product labels, and site conditions before using the Kids Room Paint Calculator result to plan materials.
Before you buy materials
- Round up to full gallons, rolls, or containers.
- Keep extra material for touchups when color consistency matters.
FAQ
How do I calculate wall area for painting?
Use wall area = 2 x (room length + room width) x wall height. Then multiply by coats and divide by coverage per gallon.
How much paint for a 12 x 12 room?
With 8 ft walls, 2 coats, and 350 sq ft per gallon, a 12 x 12 room needs about 2.19 gallons before subtracting openings or adding a separate buffer.
Should I subtract windows and doors?
For quick room estimates, many people leave openings in as a buffer. For detailed takeoffs, subtract large openings and calculate trim separately.
Does this include ceilings or trim?
No unless you add those surfaces to the area. Ceilings, trim, doors, cabinets, and decks often need separate paint or stain estimates.
Related calculators
This calculator is for planning estimates only. Verify final quantities with product labels, project conditions, and a qualified professional when accuracy matters.