Enter your room size to find out exactly how many gallons of paint you need — walls, ceiling, trim, doors, and multiple coats all accounted for.
The formula is: paintable area ÷ coverage per gallon × number of coats. One gallon of paint typically covers 350–400 square feet per coat. This calculator measures all four walls plus the ceiling, then subtracts space for doors and windows so you don't overbuy.
For most repaints over a similar color: 1–2 coats. Going from dark to light, or painting new drywall: 2–3 coats. Using a primer first reduces the number of finish coats needed and improves color accuracy.
| Finish | Coverage per gallon | Best for |
|---|---|---|
| Flat / Matte | 350–400 sq ft | Ceilings, low-traffic walls |
| Eggshell | 350–400 sq ft | Living rooms, bedrooms |
| Satin | 300–350 sq ft | Kitchens, bathrooms |
| Semi-gloss | 300–350 sq ft | Trim, doors, cabinets |
| Gloss | 250–300 sq ft | Furniture, accent pieces |
Always buy a little more than the minimum — a quart (0.25 gal) extra is usually enough for touch-ups. Paint leftover in a sealed can keeps for 2–5 years if stored at room temperature. Label the can with the room and color code for easy future touch-ups.