How to use this estimate
Divide an L-shaped room into two non-overlapping rectangles. Measure each separately and add areas, rather than adding widths and lengths before multiplying. Keep the second rectangle at zero if you only have one. Area to subtract can represent a shaft, built-in feature or another surface that should not receive material.
The calculation
A worked example
Two non-overlapping rectangles of 12 × 10 ft and 6 × 4 ft total 144 ft². Subtract a 4 ft² opening to leave 140 ft² (13.0064 m²).
This computes geometric surface area, not legally defined living space or real-estate floor area. Material waste is handled by the relevant purchasing calculator.
Common questions
How do I enter feet and inches?
Use decimal feet in imperial mode: 10 ft 6 in is 10.5 ft. Inches divided by 12 gives the fractional foot.
References & method
Rectangle area reference. See how we check calculations. Reference links provide context; no supplier endorses this site.