How to use Shape Area Calculator
- Choose the shape you are measuring.
- Pick the unit your measurements are already in.
- Enter the dimensions that shape needs; the other boxes stay hidden.
- Select Calculate and read the area, formulas, sides or perimeter. SSA triangle inputs can produce two solutions.
Example: Shape Area Calculator
Measure a rectangular floor and read the area in square meters.
Options
- Shape
- Use Rectangle, Circle or Triangle for simple area measurements. Triangle solver accepts SSS, SAS, ASA/AAS or SSA inputs. Circle and sector accepts radius, diameter, circumference or area, plus a central angle. Polygon accepts equal sides or ordered coordinate vertices.
- Unit of the dimensions
- The answer comes back in the matching square unit, so meters give m² and feet give ft². The page converts nothing, so measure in one unit before you enter the numbers.
- Decimal places
- Choose 0, 2, 4 or 6 places. Simple area modes retain your original dimensions in the formula. Triangle, sector and polygon solver results round all displayed measurements to that choice.
Supported inputs and limits
Where your input is processed
This tool processes your input in this browser. Your text and files are not uploaded to UseFreeTools. Check this tool's limits for anything it may save on your device.
Why the unit is squared
Length covers one dimension, so it is measured in a single unit. Area covers two dimensions, so the unit multiplies by itself: one square meter is a meter wide and a meter long. That is why a length converter answers in plain meters while this page answers in square meters, and why mixing feet with meters breaks the result.
Pi is a ratio, not a rounded number
The circumference of every circle is a little over three times its diameter, and that ratio is pi. Its decimal expansion never ends, so any circle area written as a decimal is an approximation at some precision. The page carries a long value of pi through the arithmetic and reports both the rounded area and the exact multiple of pi, so you can see what was rounded and by how much.
Questions about Shape Area Calculator
Why is the circle area shown as rounded?
A circle area is pi multiplied by the radius squared, and pi has no exact decimal form. The page shows the result at your chosen precision, says that it rounded, and also reports the exact multiple of pi, such as 25π m².
Does the triangle height run along the base?
No. The height is the perpendicular distance from the base to the opposite corner. A slant side is longer than that distance and would give too large an area.
Can I mix meters and centimeters in one calculation?
No. Enter every dimension in one unit and read the area in that unit squared. Convert the measurements yourself first, or the area will be wrong.
Does it work out the perimeter as well?
Rectangle results include perimeter. Triangle solver, Circle and sector, and Polygon also return perimeter. The simple base-and-height triangle mode gives only area because those inputs do not determine all three sides.
Why can side-side-angle inputs give two triangles?
When the known angle is not between the two known sides, the opposite vertex can sometimes fall in two positions. The solver shows both valid triangles instead of choosing one silently.