What this calculator actually models
Paint quantity depends on net surface area, number of coats and the coverage stated for the actual product. Instead of assuming one door size or one universal coverage rate, this calculator keeps openings, coats, coverage, waste and package size editable.
How to use this calculator
Choose imperial or metric units and enter room length, width and height.
Enter the combined area of doors/windows to exclude, select ceiling inclusion and set wall/ceiling coats.
Use the coverage printed on the paint product, then optionally enter container size and price to round to whole containers.
Where people use it
- •Room and office repaint planning
- •Comparing one-coat and multi-coat scenarios
- •Estimating package count before requesting a supplier quote
Example: 12 × 10 × 8 ft room
With 20 sq ft of openings, two wall coats, one ceiling coat and 350 sq ft per gallon coverage, the coated area is 784 sq ft. That is about 2.24 gallons before any waste allowance or package rounding.
Assumptions and limits
- •Coverage varies by product, surface porosity, color change, application method and manufacturer. Use the label or technical data for the paint you will actually use.
- •This is a quantity estimate, not a coating specification. Primer, repairs, texture, overspray and supplier pack sizes can change the purchase quantity.
Frequently asked questions
How much area does one gallon or liter of paint cover?+
There is no single value for every coating. Enter the coverage printed on the product label or technical data sheet.
Should I subtract doors and windows?+
Yes when you do not intend to paint them. Enter their combined actual area rather than relying on a generic door/window assumption.
Why are wall and ceiling coats separate?+
Walls and ceilings may use different products or coat counts, so the calculator keeps those coated areas separate before totaling paint volume.
Semantic next steps
Continue the calculation
These links move to a different input, formula or project stage rather than a keyword variation of this page.
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