Free · Walls & finishes
Room Paint Quantity & Cost Calculator
Estimate wall paint after subtracting doors and windows, with coats and coverage.
- Formula & worked example
- Private in your browser
- No signup
Your calculation
- Total door area
- 1.8 m²
- Total window area
- 0.54 m²
Use one currency for your figures. Mixed-currency conversions use rates captured October 5, 2026, rather than live exchange rates.
How to use this calculator
- Enter the values you know in the units shown. Leave unknown values blank.
- Results update automatically as you type. Edit a result to calculate another value, or lock a value to keep it fixed.
- Reset restores the starting fields. A worked example appears below.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
Calculate wall area, subtract door and window openings, multiply by the number of coats, and divide by paint coverage. Use the product's stated coverage and allow separately for surface condition and application losses.
Net area = wall area − door area − window area; paint volume = net area × coats ÷ coverage; cost = paint volume × cost per volume.
Worked example
Enter these known values and leave the other values blank.
- Room length
- 5 m
- Room width
- 4 m
- Room height
- 2.5 m
- Door height
- 200 cm
- Door width
- 90 cm
- Number of doors
- 1
- Window height
- 90 cm
- Window width
- 60 cm
- Number of windows
- 1
- Desired number of coats
- 1
- Paint efficiency
- 16 m² / L
- Room wall area
- 45 m²
- Total door area
- 1.8 m²
- Total window area
- 0.54 m²
- Total area to be painted
- 42.66 m²
- Volume of paint needed
- 2.666 L
Assumptions and limitations
- Inputs must satisfy the validation rules. Editing a result can recalculate an earlier input; lock values you want to keep fixed.
- Currency conversions use the captured source rates from October 5, 2026; they are not live exchange rates.
Common questions
What does this paint calculation tell me?
Calculate wall area, subtract door and window openings, multiply by the number of coats, and divide by paint coverage. Use the product's stated coverage and allow separately for surface condition and application losses.
Can I calculate a different unknown?
Yes. Clear that field and enter the other known values. The calculator uses the available inverse equations.
References
The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.
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