Paint Calculator
Enter your wall or ceiling dimensions to find out how many gallons of paint to buy. Adjust the number of coats and waste percentage to fit your project.
Total area: 100.0 sq ft
Gallons needed: 1
How it works
Enter each wall's length and height in feet. Add multiple walls or ceiling sections with the + Add area button.
Standard interior paint covers about 350 sq ft per gallon per coat. The calculator multiplies total area by your coat count, then divides by 350 to get gallons.
Add a waste percentage for trim losses and touch-ups — typically 10% for simple rooms and up to 15% for rooms with many openings.
Reference chart
Paint coverage by room size (1 coat, 350 sq ft/gallon; assumes 8 ft ceilings, excludes openings)
| Room size | Wall area (sq ft) | Gallons (1 coat) |
|---|---|---|
| 10×10 ft | 320 | 1 |
| 12×12 ft | 384 | 2 |
| 14×14 ft | 448 | 2 |
| 20×20 ft | 640 | 2 |
| Open plan 30×20 | 800 | 3 |
Frequently asked questions
How many square feet does a gallon of paint cover per coat?
Most interior latex paints cover 350–400 sq ft per gallon per coat. Use 350 sq ft/gal as a conservative estimate. Check your specific paint's label for exact coverage.
When do I need two coats of paint?
Use two coats when painting over a dark color, switching from a warm to cool tone, or when the wall has never been painted. New drywall with primer needs at least two finish coats.
Does primer count toward my paint gallon estimate?
No — primer and finish paint are calculated separately. Primer typically covers 200–300 sq ft per gallon. Run the calculator twice: once for primer, once for finish coats.