How to use this calculator
- Enter your own values in the labeled fields. Check the units and assumptions before comparing results. Only the fields needed for your selected calculation mode are shown.
- Your answer updates automatically. Review the calculation steps to see exactly how it was calculated.
- Copy, share, save, or download your result. Saved inputs stay on this device.
How the calculation works
Use one length unit consistently. For a complicated floor plan, split it into non-overlapping rectangles and choose multiple rooms. A triangle requires a perpendicular height, not the length of an angled side. The supporting result converts total area using the exact international-foot definition.
A worked example
A 12 ft by 10 ft room has 120 ft², equivalent to 11.1483648 m².
Reading your result
Use the main result together with its units and supporting figures. Display values are rounded; calculations keep their underlying precision. A change in inputs or assumptions can change the answer. Compare the step-by-step working with your intended use before relying on an estimate.
Frequently asked questions
Can I add several rooms?
Yes. Select multiple rooms and enter one rectangle per line.
Does it include waste?
No. Use Flooring or Tile to add a purchasing allowance.
Sources & methodology
NIST: international unit conversion factors ↗
Formula review: October 24, 2026. Read our methodology.