Area Calculator
Free, with no sign up. Calculations run on your device; your entries stay in this browser.
Calculate rectangle, circle, triangle or L-shaped area. The selected squared unit appears first; this page does not calculate arbitrary polygons or three-dimensional surface area. 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); NIST SP 811 conversion factors (1 international foot = 0.3048 m exactly).
Worked example
A 12 m × 10 m rectangle has area 120 m². A circle of radius 5 m has area 25π ≈ 78.53981634 m². Add them as separate, non-overlapping rows for 198.5398163 m². An L-shape with outer dimensions 12 m × 10 m and a 4 m × 3 m cutout has area 108 m².
Use this area in the Flooring Cost Calculator for a material estimate.
How to use this tool
Choose one length unit for all shapes, add rows and enter positive dimensions. Select Calculate for total area in the selected square unit, square feet and square metres.
Frequently asked questions
Which shapes can I calculate?
Rectangles, circles using radius, triangles using perpendicular height, and L-shapes using an outer rectangle minus a corner cutout. Arbitrary polygons and surface areas are outside this page.
Which units does the area use?
Select feet, inches, yards, metres or centimetres for every dimension. The total appears first in that unit squared, followed by square feet and square metres.
Can I add several areas?
Yes. Add up to 100 non-overlapping shapes. For an L-shape each cutout dimension must be smaller than the corresponding outer dimension.