The tin says 350 square feet. That is the second coat on a sealed surface. The first coat on bare drywall covers closer to 200, and that gap is why people run out.
Openings deducted in full here — unlike board, paint really does not go on a door.
Doors 21 sq ft, windows 12 sq ft. Trim is figured separately because it takes a different paint.
Paint tins quote a spread rate around 350 to 400 sq ft per gallon. That figure describes a smooth, sealed surface — a wall that has been painted before, or primed.
Bare drywall is not that. It is two materials with different porosity: paper facing, and joint compound over every seam and screw. Both drink paint, and they drink at different rates, which is why an unprimed wall shows every joint as a dull patch once it dries. That is flashing, and no number of finish coats hides it properly.
So the first coat over bare board covers closer to 200–250 sq ft per gallon, and the second gets you back to the number on the tin. This calculator figures each coat separately.
| Surface | First coat | Later coats |
|---|---|---|
| Bare drywall | 225 sq ft | 375 sq ft |
| Primed or painted | 350 sq ft | 375 sq ft |
| Light texture | 250 sq ft | 300 sq ft |
| Heavy texture / masonry | 150 sq ft | 200 sq ft |
On new drywall it is the coat that makes the other two work. It seals the porosity difference between paper and compound so the finish lays down evenly, and it is cheaper per gallon than finish paint.
Tinted primer earns its place on a strong colour change. Grey-tinted primer under a deep red saves a full finish coat, which is both cheaper and faster than the third coat it replaces.
Only when repainting a similar colour on a sound sealed wall. Otherwise the finish is uneven in raking light, and it shows most on the walls people look at.
Roughly a quart per 100 linear feet of baseboard, more for casing and crown. Trim paint is usually a different product and sheen, so it is a separate order.
Ceilings are often textured, and a roller overhead lays down heavier. Flat ceiling paint is formulated for it, which is another reason not to just use wall paint.