Math and measurement tools
Area Calculator
Calculate rectangle, circle, triangle and trapezoid areas in metric or imperial units. Compare square metres, square feet, hectares and acres, then save the result.
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How to use this tool
1. Choose a shape and the unit used for all dimensions. For circles enter the radius, not the diameter.
2. Enter the visible dimensions. Triangle and trapezoid heights must be perpendicular to the base, not sloping sides.
3. Calculate to see the area in your chosen unit and common land-area units. Copy or print the result before changing inputs.
Area formulas
Rectangle: length × width. Circle: π × radius². Triangle: base × perpendicular height ÷ 2. Trapezoid (trapezium): the sum of the parallel sides × perpendicular height ÷ 2. Unit conversion squares the length factor.
Worked example
A rectangle measuring 5 m by 4 m has area 20 m², approximately 215.2782083 ft², or 0.002 hectares. This is surface area only; it does not include waste or material thickness.
Questions and assumptions
Measuring irregular spaces
Split an irregular space into non-overlapping supported shapes and add their areas. Subtract openings separately. Curved ground, map projections, boundary uncertainty and legal surveys are outside this calculator.
Precision and units
Dimensions support up to six decimals and results show up to ten significant digits. All dimensions in a calculation use the same unit. Converted figures are rounded and should not imply greater measurement precision.
Sources and further reading
Built and maintained by Custom Logic. Page updated .