Painting
Paint & Cost Calculator
Estimate wall area and gallons of paint for a rectangular room using coats, coverage per gallon, and optional waste, plus a rough cost from your own price per gallon and national-average paint cost ranges for context.
Calculator inputs
Paint Calculator Results
Results update in your browser as you edit inputs. They are planning estimates, not complete shopping lists.
Enter project dimensions to calculate material quantity.
Assumptions
- The room is treated as a rectangle.
- Doors and windows are subtracted only when you enter counts and average opening areas.
- Ceilings, trim, primer, and surface repairs are not included.
- Coverage per gallon should come from the paint label.
- For buying paint, use the rounded whole-gallon quantity or the container sizes available for your product.
- Cost outputs use only the unit prices you enter.
Formula
- Wall area = 2 x (room width + room length) x wall height.
- Paintable wall area = wall area minus optional door and window area.
- Coated area = paintable wall area x number of coats.
- Gallons needed = coated area divided by coverage per gallon.
- Gallons with waste = gallons needed x (1 + waste factor).
How to Use the Paint Calculator
- Enter room width, room length, and wall height.
- Enter the number of coats you plan to apply.
- Use the coverage per gallon from the paint label, not a generic promise.
- Subtract doors and windows only when you want a tighter wall-area estimate.
- Review gallons before rounding and the rounded whole-gallon equivalent before buying.
Paint Calculator Examples
12 ft x 12 ft room with two coats
A 12 ft by 12 ft room with 8 ft walls has 384 sq ft of wall area. Two coats at 350 sq ft per gallon need about 2.2 gallons before waste, so the whole-gallon equivalent is 3 gallons.
- Wall area: 384 sq ft
- Coated area: 768 sq ft
- Coverage: 350 sq ft/gal
- Rounded whole-gallon equivalent: 3 gal
10 ft x 10 ft room with one coat
A 10 ft by 10 ft room with 8 ft walls has 320 sq ft of wall area. One coat at 350 sq ft per gallon needs about 0.91 gallons before waste.
- Wall area: 320 sq ft
- Coats: 1
- Coverage: 350 sq ft/gal
- Liquid estimate: about 0.91 gal
Units and Parameters Quick Reference
Paint inputs and coverage
Coverage can vary by surface texture, color change, primer, and product type.
| Input | Unit | Planning note |
|---|---|---|
| Room dimensions | ft | Used to calculate wall perimeter and wall area. |
| Wall height | ft | Use the painted wall height. |
| Coats | count | Two coats doubles the coated area. |
| Coverage | sq ft/gal | Use the paint label. |
| Openings | count | Optional rough deductions for doors and windows. |
This calculator estimates wall paint only unless you add your own assumptions for primer, trim, or ceiling paint.
How much does it cost to paint a room?
Beyond gallons, most people also want to know the cost to paint a room. As a national-average planning range, wall paint materials run about $0.30 to $0.60 per square foot of wall for two coats, while hiring a professional painter typically costs about $2 to $6 per square foot of wall including labor. The difference is almost entirely labor, which is why doing it yourself is usually much cheaper on cash outlay.
These ranges are national averages for context only, not a local quote, and they cover walls rather than ceilings, trim, or repairs. This calculator never uses live or local prices: to get a material-only number, enter your own price per gallon and it will multiply that by the estimated gallons. For a hired job, always confirm with local painters, since rates, prep, and access vary by region.
Cost to paint a room (national average)
Approximate U.S. national-average planning figures for wall paint, not a local quote. Actual cost varies by paint grade, coats, prep, ceiling and trim, and region.
| Room | DIY materials (paint and supplies) | Hire a painter (walls, with labor) |
|---|---|---|
| Small room / 10x10 (about 320 sq ft walls) | $30 to $70 | $250 to $550 |
| 12x12 room (about 384 sq ft walls) | $40 to $90 | $300 to $700 |
| Large room / 16x20 (about 576 sq ft walls) | $60 to $130 | $450 to $1,000 |
National-average ranges for planning only, not a local quote. DIY figures assume mid-grade paint and two coats on walls; hired figures include labor. Confirm pricing with local paint suppliers and painters.
Gallons of paint per square foot
If you want to compare coverage by square foot, convert coats and label coverage into a gallons-per-square-foot planning rate.
Gallons per sq ft = number of coats / coverage per gallon x (1 + waste factor).
Quick paint coverage examples
| Scenario | Gallons per sq ft | Approx. gallons per 100 sq ft |
|---|---|---|
| 1 coat, 350 sq ft/gal, 0% waste | 0.0029 | 0.29 gal |
| 2 coats, 350 sq ft/gal, 0% waste | 0.0057 | 0.57 gal |
| 2 coats, 350 sq ft/gal, 10% waste | 0.0063 | 0.63 gal |
Surface texture, primer, color change, and actual product coverage can change the final quantity.
Example calculation
Example: 12 x 12 room
A 12 ft by 12 ft room with 8 ft walls has 384 sq ft of wall area. Two coats at 350 sq ft per gallon need about 2.2 gallons before waste.
Common mistakes
- Forgetting to multiply by the number of coats.
- Using advertised coverage when a rough surface needs more paint.
- Comparing costs without entering your own local product price.
FAQ
Does this subtract windows and doors?
Yes, if you enter door and window counts with average opening areas. Leave those fields at 0 for a quick full-wall estimate.
Does this include ceiling paint?
No. It estimates wall paint only.
How much does it cost to paint a 12x12 room?
As a national-average planning range, painting the walls of a 12x12 room costs roughly $40 to $90 in DIY materials (about 2 to 3 gallons of mid-grade paint plus supplies), or roughly $300 to $700 if you hire a painter, depending on prep, ceiling and trim, number of coats, and your region. These are national averages for context, not a local quote. For a material-only number, enter your own price per gallon and the calculator multiplies it by the estimated gallons.
Is it cheaper to paint a room yourself or hire a painter?
Doing it yourself is almost always cheaper on cash outlay because you skip labor, which is the largest part of a professional quote. A typical room might cost $40 to $90 in DIY paint and supplies versus $300 to $700 hired out, as a national-average range. Hiring a painter costs more but saves time and usually gives a cleaner finish on detailed or high rooms. These figures are national averages, not a local quote.
How much does paint cost per square foot?
Paint material alone usually works out to about $0.30 to $0.60 per square foot of wall for two coats, based on a gallon covering roughly 350 square feet and mid-grade paint priced around $25 to $50 per gallon. Hiring a painter typically runs about $2 to $6 per square foot of wall including labor. These are national-average planning ranges, not a local quote; enter your own gallon price for a material-only estimate.
How many gallons of paint do I need per square foot?
Divide the number of coats by the coverage per gallon. For two coats at 350 sq ft per gallon, the rate is about 0.0057 gallons per square foot before waste.
Does this calculate primer?
No. Primer coverage and need depend on surface condition, color change, and product instructions.
Related Planning Tools
Use these related calculators when the same project needs another material estimate. Each link opens a browser-based tool with its own assumptions and formulas.