Circle Calculator
All Circle Measurements โก
Enter any one value โ radius, diameter, circumference, or area โ and instantly calculate all the others.
Enter any one value โ radius, diameter, circumference, or area โ and instantly calculate all the others.
All circle measurements relate to each other through ฯ (pi โ 3.14159):
What is ฯ (pi)?
Pi is the ratio of a circle's circumference to its diameter. It is approximately 3.14159265 and is irrational โ its decimal places go on forever without repeating. This calculator uses the full precision value built into JavaScript.
What is the difference between radius and diameter?
The radius is the distance from the centre of a circle to its edge. The diameter is the distance across the full width of the circle through the centre โ exactly twice the radius.
What is circumference?
The circumference is the perimeter of a circle โ the total distance around its edge. For a circle with radius 5, the circumference is 2 ร ฯ ร 5 โ 31.416.
What units does this calculator use?
The calculator works with any unit โ cm, m, inches, feet. If you enter the radius in cm, all results are in cm (for linear measurements) and cmยฒ (for area). Always use consistent units.