circle
area: 78.54
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Geometry calculator
Area, perimeter or volume of a shape – with formula and worked example.
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FAQ
Frequently asked questions
Which shapes can I calculate?
Circle, square, rectangle, triangle, cylinder and sphere - each with area and circumference or volume and surface.
How do I calculate the area of a circle?
The circular area is A = π × r². With a radius of 5 that comes out to around 78.54.
What unit does the result have?
The unit follows your input. If you enter centimeters, the area is in cm² and the volume is in cm³.
How is the area of a triangle defined?
This calculator uses A = base × height / 2. The height is perpendicular to the base.
How is the volume of the sphere calculated?
With V = 4/3 × π × r³, the surface with O = 4 × π × r².
What value is used for π?
The calculator uses the full value of Pi and first rounds the result.
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Sources and notes
Rule status and context
- Formulas
- Circle A = π r², rectangle A = a b, triangle A = a h/2, cylinder V = π r² h, sphere V = 4/3 π r³.