Paint Calculator & Estimator
Free paint calculators for a single room, whole house, exterior, primer and trim, plus cost and color-change estimates.
Your room sizes and paint figures never leave this page — every calculation runs right here in your browser. Calculate your room →Private by design
Every figure is calculated in your browser. Room sizes and paint amounts never leave the page, and there are no accounts to sign up for.
Real coverage rates
Tools use the industry-standard 350 to 400 square feet per gallon for latex paint, with surface and waste adjustments you can set yourself.
Plan every surface
From a single wall to whole-house, exterior, primer, ceiling and trim, each calculator plans the exact gallons for the job in front of you.
All calculators and guides
Single Room Calculator
Walls, doors, windows, coats and waste in exact gallons for one room.
Whole House Calculator
Estimate paint across several rooms from a room count and average size.
Exterior Paint Estimator
Perimeter, wall height and siding type for the outside of the house.
Primer, Ceiling & Trim
Plan primer, ceiling and trim together with the walls in one estimate.
Paint Cost Calculator
Turn gallons and store prices into a full project budget.
Color Change Coats
See how many extra coats a dark-to-light switch needs.
Coverage Reference Guide
How far a gallon goes on different surfaces.
How these tools work
Start with the room calculator above — it is the same tool as the single-room page, right on the home page so you can get a number in seconds. Enter the room length, width and wall height, count the doors and windows, pick your coverage and coats, and the tool returns the gallons to buy.
Below the calculator you will find dedicated tools for a whole house, the exterior, primer with ceiling and trim, project cost, and color changes. Each one uses the same industry-standard coverage rates, so the numbers stay consistent across your project. Pick the scenario that matches your job, or use the whole-house tool to budget everything at once.
Every figure is computed in your browser. Nothing you type is uploaded or stored, which keeps the site fast and private.
Plan a paint job in three steps
Enter your room
Type the length, width and wall height, then count the doors and windows you will not paint. Pick your coverage and number of coats.
Get exact gallons
The calculator subtracts openings, applies your coats and a waste allowance, and rounds up to whole gallons so the number matches how paint is sold.
Buy with confidence
Use the result to shop once, avoid a second trip, and keep a little extra for touch-ups. Re-run it for every room on the project.
FAQ
How much paint do I need for a 12x12 room?
A 12 ft by 12 ft room with 8 ft ceilings has about 384 sq ft of wall before openings. Subtract two doors and one window (about 57 sq ft) and you get roughly 327 sq ft of net wall. At 350 sq ft per gallon and two coats with 10 percent waste, plan on about 2 gallons of paint. The calculator above does this automatically for any size.
How many coats of paint do I need?
Two coats are standard for even, opaque coverage on a repainted wall. A dark-to-light color change often needs a third coat or a tinted primer first. New drywall or bare wood needs primer plus two top coats. The calculator adds the extra coat automatically when you pick a color change.
How do I subtract doors and windows?
Count each door as 21 sq ft and each window as 15 sq ft of wall you do not paint. A room with two doors and three windows therefore skips about 87 sq ft. Enter the counts above and the tool removes them from the gross wall area before dividing by coverage.
What coverage should I use?
Most latex wall paint covers 350 to 400 sq ft per gallon on smooth, repainted walls. Textured or new drywall absorbs more, so use 250 to 300. Check the label on your can; the calculator lets you set the exact number.
Do I need primer?
Primer is recommended on new drywall, bare wood, stained or glossy surfaces, and for dramatic color changes. On previously painted smooth walls, two top coats usually work without primer. See the primer, ceiling and trim calculator for a combined estimate.
Why buy about 10 percent extra?
A 10 percent waste allowance covers touch-ups, roller drag, and small coverage differences between brands. Running out mid-project means a second trip and possible color-match trouble on a fresh batch.