Formula and calculation method
Rectangle = ab. Triangle = ab/2. Circle = πa². Ellipse = πab.
Use consistent units for all comparable inputs. The displayed result is rounded; arithmetic is performed with the full available numeric precision. Check your source measurements before relying on the result.
How to use area calculator
- Set Shape by choosing the option that matches your calculation.
- Set Length / base / radius. The example below uses 5.
- Set Width / height / second radius. The example below uses 4.
- Select Calculate to update the result. Reset restores the illustrated inputs. Copy, print or download your own result if you need a record.
Worked example
Example inputs
- Shape
- Rectangle
- Length / base / radius
- 5
- Width / height / second radius
- 4
- Area (square units)
- 20
Factors affecting your result
Use consistent units for all comparable inputs. The displayed result is rounded; arithmetic is performed with the full available numeric precision. Check your source measurements before relying on the result.
Changing shape changes the scenario being evaluated. Adjust one input at a time when comparing results, keep a copy of the assumptions, and compare values using the same unit and period. A precise arithmetic result does not make an uncertain assumption precise.
Frequently asked questions
How does the area calculator work?
Rectangle = ab. Triangle = ab/2. Circle = πa². Ellipse = πab.
What inputs does Area Calculator need?
Enter shape, length / base / radius, width / height / second radius. Choose values that correspond to the same situation and measurement convention.
How should I interpret the area calculator result?
Use consistent units for all comparable inputs. The displayed result is rounded; arithmetic is performed with the full available numeric precision. Check your source measurements before relying on the result.
Are my area calculator inputs uploaded?
No. The calculation runs in this browser. Favorites, recent tool names, theme and formatting preferences may be saved locally, but calculation inputs are not sent to a calculation server or stored by this website. Shared links do not include entered values.
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