What is the Circle Calculator?
Know just one measurement of a circle? Enter the radius, diameter, circumference or area and get all the others instantly. Add an angle to also find the arc length and sector area – handy for pizza slices, round tables, wheels, pipes and geometry homework.
How to use the Circle Calculator
- Choose what you know (radius, diameter, circumference or area).
- Enter the value.
- Optionally enter a sector angle in degrees.
Circle formulas
- Diameter d = 2r
- Circumference C = 2πr = πd
- Area A = πr²
- Arc length = (θ/360) × 2πr
- Sector area = (θ/360) × πr²
This Circle Calculator is 100% free, needs no signup and runs privately in your browser – on phone, tablet or computer.
Last updated: · By NodifyTech