Whole House Paint Calculator — Multiple Rooms
Free whole house paint calculator: add each room size to estimate total paint, primer and cost.
All the math happens locally, so your room sizes never leave the page — no sign-up, no tracking.Try: Number of rooms=4, Average room length=12, Average room width=12, Wall height=8, Doors per room=1, Windows per room=1, Coverage per gallon=350, Number of coats=2, Waste factor=15 → 4, 348 sq ft, 1392 sq ft, 2, 9.15 gal, 10 gallons
How to use
The whole-house tool estimates paint for several rooms at once. Enter how many rooms you are painting and their average length, width and height, plus the typical doors and windows per room. The calculator totals the net wall area across all rooms, applies your coats and a waste factor, and tells you how many gallons to buy.
This is the fastest way to budget a move or a full repaint. For rooms that differ a lot in size, measure the largest and smallest and use a middle value, or run the single-room tool on the outliers. Ceilings are not included here — use the primer, ceiling and trim calculator when you need them planned together.
Two coats are the default, but bump to three on bold color changes or on open-plan walls that catch the light. The waste factor covers roller drag, cut-in edges and the awkward corners where coverage dips. If you plan to paint the ceilings too, run the primer, ceiling and trim calculator and add those gallons to the wall total above so the whole project is on one shopping list.
FAQ
How do I estimate paint for a whole house?
Add up the wall area of every room, then apply your coats and a waste factor. The quick method above averages one room size and multiplies by the room count — good for a budget before you shop. For precision, measure each room individually.
Should ceilings be included?
This whole-house tool focuses on walls. Add ceilings separately: a 12x12 room ceiling is 144 sq ft, or about 0.5 gallon at 350 sq ft per gallon with two coats and waste. The primer, ceiling and trim calculator plans ceilings alongside walls.
How much extra for a big house?
Larger homes need more coats on open-plan walls and more cut-in work. Keep the 10 to 15 percent waste factor and consider an extra gallon so you can finish a room from the same batch.