Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Paint needed
2.00
Estimated paint cost
$90
Paintable wall area
344
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter room length (ft).
- 2Enter room width (ft).
- 3Enter ceiling height (ft).
- 4Enter doors and windows area (sqft).
- 5Enter number of coats.
- 6Enter price per gallon ($).
- 7Read your paint needed on the right — it updates as you type.
- 8Hit Share to keep the scenario or send it to someone.
About this calculator
12x12 is a standard bedroom size in most homes. This calculator defaults to that footprint with 8-foot ceilings and two coats, returning the gallons of paint needed and total cost, editable for any color coverage rate or door/window deduction.
Worked example
Using the values the calculator loads with:
Inputs
- Room length: 12 ft
- Room width: 12 ft
- Ceiling height: 8 ft
- Doors and windows area: 40 sqft
- Number of coats: 2
- Price per gallon: 45 $
Results
- Paint needed: 2
- Estimated paint cost: $90
- Paintable wall area: 344
What each field means
Inputs
- Room length (ft)
- The room length used in the calculation, measured in ft. Starts at 12 ft so you have a working example on load.
- Room width (ft)
- The room width used in the calculation, measured in ft. Starts at 12 ft so you have a working example on load.
- Ceiling height (ft)
- The ceiling height used in the calculation, measured in ft. Starts at 8 ft so you have a working example on load. Accepted range: 6–14 ft.
- Doors and windows area (sqft)
- The doors and windows area used in the calculation, measured in sqft. Starts at 40 sqft so you have a working example on load.
- Number of coats
- The number of coats used in the calculation. Starts at 2 so you have a working example on load. Accepted range: 1–3.
- Price per gallon ($)
- The price per gallon used in the calculation, measured in $. Starts at 45 $ so you have a working example on load.
Results
- Paint needed
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Estimated paint cost
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Paintable wall area
- Returned as a whole number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How many gallons of paint for a 12x12 room?
About 2 gallons for two coats at 8-foot ceilings, though a single gallon can cover one coat if you're just refreshing an existing color.
Should I buy primer separately?
Yes, if changing from a dark to a light color or painting new drywall, budget for a separate primer coat — this calculator assumes same-color repaint coverage.
How much does trim and baseboard paint add?
Trim paint is bought separately in quarts typically, and isn't included in this wall-area gallon estimate.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). 12x12 Room Paint Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/12x12-room-paint-calculator
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/12x12-room-paint-calculator" target="_blank" rel="noopener">12x12 Room Paint Calculator — RevenueLab</a> (2026).</p>
Source: [12x12 Room Paint Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/12x12-room-paint-calculator) (2026).