Quick start
- Enter the room length, width, and wall height in feet.
- Enter the number of doors, windows, coats, and paint coverage from the can or product page.
- Use extra percent when the surface is textured, patched, or you want a safer buying estimate.
Best uses
These are the situations this tool is meant for. If your task is close to one of these, the examples and notes below can help you choose the right inputs.
- Estimate gallons for a bedroom, office, or living room.
- Adjust for one or two coats before buying paint.
- Subtract common doors and windows from wall area.
- Compare coverage values from different paint labels.
What this calculator is solving
The Paint Calculator estimates interior wall paint for a simple room. It starts with wall area, subtracts typical door and window areas, then applies coats, coverage, and extra percent.
You do not need to memorize the formula first. Start by matching each input label on the calculator to the number, date, unit, or setting you actually have.
The formula in plain language
In plain language: The calculator finds wall area from room perimeter and height, subtracts estimated doors and windows, multiplies by coats and extra percent, then divides by square-foot coverage per gallon. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
If that sounds abstract, use the example cards on the calculator page. They show a complete set of inputs and the kind of answer you should expect.
How to read the answer
Read the headline result first. Then look at the smaller supporting lines because they explain the parts behind the answer, such as totals, units, ranges, or formula steps.
- Gallons to buy rounds the calculated need up to whole gallons.
- Paintable wall area shows the wall estimate after subtracting openings.
- Coverage used reminds you which square-feet-per-gallon assumption drove the result.
Common mistakes to avoid
If the answer looks strange, the most likely cause is a small input mismatch: the wrong unit, date, weight, scale, mode, or policy assumption.
- Do not use floor square footage as wall square footage.
- Do not forget that two coats roughly doubles the paintable area.
- Check the actual product label because coverage varies by paint, surface, color, and primer.
Research and references
These references shaped the calculator assumptions, unit choices, or safety notes.
Examples from the calculator
Gallons to buy
Paintable area and gallons
Low paint estimate
FAQ in plain language
When should I use the Paint Calculator?
Use it when your task matches one of these common needs: Estimate gallons for a bedroom, office, or living room. Adjust for one or two coats before buying paint. It works best when you already know the values, dates, units, or settings the page asks for.
What is the Paint Calculator doing with my inputs?
In plain language: The calculator finds wall area from room perimeter and height, subtracts estimated doors and windows, multiplies by coats and extra percent, then divides by square-foot coverage per gallon. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What should I double-check before trusting the answer?
Paint coverage depends on product, primer, surface texture, color change, application method, and how much paint remains in the can or tray. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
Related tools
- Square Footage Calculator Calculate square feet, square yards, and square meters from length, width, and quantity.
- Drywall Calculator Estimate drywall sheet count from project area, sheet size, and waste percentage.
- Tile Calculator Estimate tile count from area, tile size, and waste percentage.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to paste the expression and result into notes, homework, a message, or another document. Check the units and assumptions before copying.