Paint Calculator
Find out how much paint you need for walls and ceilings. Estimate paint quantity, coverage, multiple coats, doors, windows, and paint and labor costs using your room dimensions and local prices.
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Paint Guide
How to Estimate Paint for Your Project
Estimating paint starts with measuring the surfaces you plan to paint. For a room with four walls, measure the room length, width, and wall height. For a ceiling-only project, use the ceiling dimensions. Subtract openings, account for the number of coats, and use the coverage printed on the paint product.
If you need help checking floor dimensions, use our area calculator. For a separate flooring project, our tile calculator can help estimate tile quantities.
1. Measure the Room
Measure length, width, and wall height. Keep units consistent and measure each surface you want to paint.
2. Account for Openings
Enter the number of doors and windows. The calculator uses estimated opening areas, which may not match your actual measurements.
3. Set Coats and Coverage
Enter the number of coats and the coverage rate from the paint label. Coverage may be listed in square feet per gallon or square meters per liter.
4. Estimate Your Budget
Enter the paint price and, if needed, the labor rate. Review the estimated quantity and costs before purchasing.
How to Use the Paint Calculator
- Choose the project type. Select the available option that matches your project, such as room walls or ceiling.
- Enter dimensions. Add the required length, width, and height measurements. Choose the appropriate measurement units.
- Enter openings and coats. Provide the number of doors and windows, then set the number of coats you plan to apply.
- Check paint coverage. Use the coverage rate on your paint can rather than assuming every paint product covers the same area.
- Enter prices and calculate. Enter the applicable paint price and labor rate, then use the calculator's action button to view the estimate.
- Review the result. Check the paintable area, required paint quantity, suggested purchase quantity, and estimated costs before buying.
Tip: Double-check the selected units and coverage rate. Entering coverage per liter while using gallons, or mixing measurement units, can produce an inaccurate estimate.
Paint Calculator Example
Consider a room that is 12 feet long, 10 feet wide, and 8 feet high. This example estimates wall paint only and assumes one door, one window, two coats, and coverage of 350 square feet per gallon.
| Gross wall area | 2 × (12 + 10) × 8 = 352 sq ft |
|---|---|
| Estimated openings | 21 + 15 = 36 sq ft |
| Paintable wall area | 352 − 36 = 316 sq ft |
| Area for two coats | 316 × 2 = 632 sq ft |
| Paint required | 632 ÷ 350 ≈ 1.81 gallons |
At this coverage rate, the estimate is approximately 1.81 gallons, so the calculator's purchase recommendation may round up to 2 gallons. Actual requirements can vary with surface conditions and the paint product.
Paint Calculator Formula
Wall Area: 2 × (Length + Width) × Height
Ceiling Area: Length × Width
Paintable Wall Area: Wall Area − Door Area − Window Area
Total Area for All Coats: Paintable Area × Number of Coats
Paint Required: Total Area for All Coats ÷ Coverage per Unit
Paint Cost: Paint Quantity × Price per Unit
These formulas provide general estimates. The calculation depends on the selected project type, units, openings, coverage rate, and paint product. Ceiling-only projects use ceiling area rather than wall area.
Paint Coverage Tips
- Check the manufacturer's coverage rate on the paint label.
- Rough, textured, or porous surfaces may require more paint.
- Primer, application method, and color changes can affect coverage.
- Measure actual door and window sizes when precision matters; this calculator uses standard area estimates for openings.
- Check available container sizes and prices before purchasing. Small touch-up quantities may be useful for future repairs.
For additional product guidance, visit Sherwin-Williams homeowner painting resources. Always follow the instructions on your selected paint product.
Important: This calculator provides an estimate, not a guaranteed quantity or contractor quote. Paint coverage, actual opening sizes, container prices, surface preparation, and labor rates can change the final cost.
Paint Calculator FAQs
How much paint do I need for a room?
The amount depends on the paintable wall or ceiling area, number of coats, and coverage per gallon or liter. Enter your measurements and the coverage listed on your paint can to estimate the quantity.
How many coats of paint should I use?
Two coats are a common starting point for many interior painting projects. Follow the paint manufacturer's instructions. New surfaces, major color changes, or uneven coverage may require additional coats.
Does the calculator subtract doors and windows?
Yes. The calculator subtracts estimated door and window areas from wall area. Actual opening sizes can differ, so treat the result as an estimate.
Can I calculate paint in liters?
Yes. Select metric units to enter dimensions in meters or centimeters and calculate paint using square meters and liters. US customary units use square feet and gallons.
Can I enter feet and inches together?
Yes. Select the ft + in option and enter the feet and inches values. The calculator converts the measurements for the calculation.
Does the calculator include labor cost?
Yes. If you enter a labor rate per square foot or square meter, the calculator estimates labor separately from paint cost. Actual contractor quotes may include preparation and other charges.
Why should I check the coverage on the paint can?
Coverage varies by product, surface texture, porosity, application method, primer, and color change. Use the manufacturer's stated coverage when possible.
Why might I need to buy more paint than the estimate?
Paint is sold in specific container sizes, and real surfaces may absorb more paint than expected. The calculator rounds the purchase quantity according to its supported units, but actual coverage can vary.