Circle Area Calculator
Calculate area, circumference, diameter, and radius of a circle. Solve from any one value.
About this calculator
The Circle Area Calculator on NumberCals is a free, mobile-friendly tool for anyone needing to calculate area, circumference, diameter, and radius of a circle. solve from any one value. Enter your values in the form below and the result is computed instantly — no sign-up, no installation, no waiting.
Formula used
A = π·r²; C = 2π·r; d = 2r
What you'll need
- What you know
- Value (e.g. 5)
What you'll get
- Radius
- Diameter
- Circumference
- Area
Formula
A = π·r²; C = 2π·r; d = 2r
Result
Frequently Asked Questions
How do I find the radius from the area? +
Pick 'Area' from the dropdown and enter the value. The calculator computes r = √(A/π) and the rest.
What's the value of π used? +
Python's math.pi, accurate to ~15 decimal places.
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