Paint Calculator by Square Footage
Already know your wall area? Enter the square footage directly — no room dimension entry needed. Works for irregular rooms, floor-plan measurements, and contractor estimates.
Wall Square Footage
Enter your net paintable area after subtracting doors and windows, or your gross area — your choice.
Direct square-footage formula
gallons_to_buy = ⌈ (wall_sq_ft × coats) ÷ coverage ⌉ Enter the area you want painted. If you are including doors and windows in your measurement, leave them in — you will buy slightly more than needed, which is fine. If you have already excluded them, enter the net area.
How this differs from the room dimensions calculator
The interior paint calculator computes wall area from length, width, and ceiling height, then automatically deducts door and window openings. This calculator skips that step — you enter the paintable area in square feet directly. Use it when:
- You have measured walls individually and added them up
- You are painting only some walls, not the whole room
- Your room is L-shaped, has a bay window bump-out, or is otherwise not a simple rectangle
- You already have a sq ft figure from a contractor or floor plan
Quick reference: gallons by square footage
| Wall area | 1 coat @ 350 | 2 coats @ 350 |
|---|---|---|
| 200 sq ft | 1 gal | 2 gal |
| 334 sq ft (12×12 room) | 1 gal | 2 gal |
| 500 sq ft | 2 gal | 3 gal |
| 700 sq ft | 2 gal | 4 gal |
| 1,000 sq ft | 3 gal | 6 gal |
Frequently Asked Questions
Use the square footage calculator when you already know your paintable area — for example, from a floor plan, a contractor estimate, or a previous paint job. It is also useful for irregular-shaped rooms (L-shaped, rooms with niches) where you have measured the surface area directly rather than computing it from length and width.
Either works. If you enter gross wall area (before subtracting openings), you will buy slightly more paint than needed — which is fine for a buffer. If you have already subtracted 20 sq ft per door and 15 sq ft per window, enter the net area for a tighter estimate. The room-dimensions calculator does this deduction automatically.
Break the room into rectangles. For each wall section, multiply its width by its height. Add all the sections together. For angled or sloped walls (vaulted ceilings), measure the wall as a trapezoid: ((top width + bottom width) / 2) × height. Then enter the total.
At 350 sq ft/gal for one coat: 1,000 ÷ 350 = 2.86 gallons, so you buy 3 gallons. For two coats: 5.71 gallons, so you buy 6 gallons. At 400 sq ft/gal: 1,000 ÷ 400 = 2.5 gallons → buy 3 gallons (1 coat), 5.0 gallons → buy 5 gallons (2 coats).