Paint Calculator
Estimate how many gallons of paint you need for any room. Calculate wall area, subtract doors and windows, and get the exact amount of paint required.
Wall Dimensions
Results
Paint Coverage Guide
Our paint calculator uses 350 square feet per gallon as a conservative estimate. Here are some factors that affect paint coverage:
- Standard door: approximately 20 sq ft each
- Standard window: approximately 15 sq ft each
- Textured walls (popcorn, knockdown) use 10-20% more paint
- Dark colors and dramatic color changes may need 3 coats
- High-quality paint often provides better coverage than budget brands
How to Calculate It Yourself
If you prefer to check the math by hand, follow these steps:
- Measure the perimeter of the room and multiply by the wall height to get total square footage.
- Subtract doors (about 20 sq ft each) and windows (about 15 sq ft each).
- Multiply the net area by the number of coats you plan to apply.
- Divide by 350 (sq ft covered by one gallon) and round up to the nearest gallon.
Worked Example
A 12 x 10 ft bedroom with 8 ft ceilings has walls of (12+12+10+10) x 8 = 352 sq ft. Minus 2 doors (40) and 2 windows (30) leaves 282 sq ft. For 2 coats that is 564 sq ft, so you need 2 gallons of paint.
Approximate Material Costs
Prices vary by region and supplier. These are rough US averages to help with budgeting.
| Item | Estimate | Notes |
|---|---|---|
| 1 gallon interior paint | $30 - $50 | Covers ~350 sq ft |
| 5 gallon bucket | $100 - $200 | Biggest projects / whole house |
| Primer (1 gallon) | $25 - $40 | Adds 1 coat of coverage |
| Painting supplies | $20 - $60 | Rollers, brushes, trays, tape |
Frequently Asked Questions
How much paint do I need for a 12x12 room?
A 12x12 room with 8-foot ceilings has approximately 384 square feet of wall area. After subtracting doors and windows, you'll need about 1 gallon of paint per coat. For two coats, buy 2 gallons.
How many square feet does a gallon of paint cover?
One gallon of paint typically covers 350-400 square feet. This varies by paint quality, surface texture, and color. Darker colors and textured surfaces may require more paint.
Should I use primer before painting?
Yes, primer is recommended when painting over dark colors, new drywall, stained surfaces, or when making a dramatic color change. Primer improves adhesion and reduces the number of paint coats needed.
How many coats of paint should I apply?
Two coats of paint are standard for most interior painting projects. One coat may suffice for repainting the same color, but two coats ensure even coverage and better durability.