Free · Math · Geometry

Circle Calculator

Find diameter, circumference, area, and equations from a circle radius.

  • Checked formula
  • Private in your browser
  • No signup
Calculator inputs

Enter your values

Result

Your calculation

Area
78.53981634
square units
Circumference
31.41592654
Diameter
10
Equation at origin
x² + y² = 25

How to use this calculator

  1. Enter the known values using the units shown.
  2. Choose the calculation you want when more than one method is available.
  3. Calculate, then review the result and the worked formula together.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.