Area of a Circle Calculator
Calculates the area of a circle from the measurements you enter. Use any unit, as long as all inputs use the same one.
Result
- Area
- 78.5398
How to use the area of a circle calculator
- Enter the radius.
- The results update as you type, or press Calculate.
- Read the area first, then the supporting figures below it.
Formula
πr²
Worked example
For example, with these inputs:
- Radius: 5
the calculator returns:
- Area: 78.5398
Background
A quick mental estimate before calculating is a powerful check. If a room's floor area comes out at 4,000 square metres or a percentage comes out above 100% when it should not, you know to look again.
Each formula has assumptions built in. Area formulas assume flat shapes, volume formulas assume regular solids and statistical measures assume the data you enter is the data you want to describe. Knowing the assumptions helps you pick the right tool.
Frequently asked questions
How does the area of a circle calculator work?
It applies this formula: πr²
Can I use any units?
Yes, as long as every input uses the same unit. The answer will be in that unit (squared for areas, cubed for volumes).