"How much paint do I need?" really has two questions inside it: how big is the surface, and how many coats will it take? Get the second one wrong and even a perfect area estimate leaves you short.
Start with coverage
One gallon covers roughly 350 square feet per coat on smooth, primed walls. Textured, porous, or unprimed surfaces drink more — plan on 250–300 square feet. Our paint calculator uses 350 and lets you set the number of coats.
How many coats you actually need
- One coat: repainting a wall a very similar color, in good condition.
- Two coats: the standard for an even, durable finish — assume this unless you have a reason not to.
- Three coats: dramatic color changes, or going dark to light without primer.
When primer saves you a coat
A tinted primer can turn a three-coat job into a two-coat one. Prime when you are covering a big color change, painting over stains or patches, or coating bare drywall, wood, or masonry. Primer grips better too, so the finish lasts longer.
Do not subtract every opening
It is tempting to subtract each door and window, but leaving small ones in builds a useful buffer for touch-ups. For large openings — a picture window or a wide doorway — subtract roughly 15–20 square feet each.
Buy it all at once
Paint is mixed in batches, and color can drift slightly between them. Buy all your gallons for a room in one go, from the same batch, and you avoid a faint seam where two mixes meet. The same logic applies to deck stain.
Estimate the area, decide your coats honestly, and round up to whole gallons. That is the whole game.