Square Footage Calculator
Free, with no sign up. Calculations run on your device; your entries stay in this browser.
Choose the shape of each room and enter every dimension in the selected length unit. Add as many rooms as needed, up to 100. Use perpendicular height for triangles. For an L-shape, measure the outer rectangle and the rectangular corner cutout; rooms should not overlap.
Your result
Rectangle: A = length × width. Circle: A = πr². Triangle: A = base × perpendicular height / 2. L-shape: A = outer rectangle − corner cutout. Total = sum of rooms; m² = ft² × 0.3048².
Primary source: Massachusetts DESE mathematics reference sheet (area formulas).
Worked example
An L-shaped room with an outer 12 ft × 10 ft rectangle and a 4 ft × 3 ft cutout is 120 − 12 = 108 ft². Add a separate 8 ft × 10 ft room for a total of 188 ft².
Use this area in the Flooring Cost Calculator for a material estimate.
How to use this tool
Enter your values, choose the options, and select Calculate. Add or remove rows as needed.
Frequently asked questions
How do I measure an L-shape?
Enter the full outer length and width, then the length and width of the missing corner rectangle. Each cutout dimension must be smaller than its outer dimension.
Can I sum several rooms?
Yes. Add one row per non-overlapping room, selecting its shape and dimensions. All rows use the same selected length unit.
Does this include flooring waste?
No. It gives geometric area. The linked Flooring Cost Calculator handles flooring estimates.