Circle Calculator

Find circumference, area, arc length, sector area and chord length from a radius or diameter, with steps. Try “arc length of a sector with r = 6 and angle 75°”.

Try an example:

How the Circle Calculator works

  1. Get the radius (half the diameter).
  2. Use C = 2πr and A = πr², or arc = (θ ÷ 360) × 2πr for an angle in degrees.
  3. Substitute, simplify and give your answer in terms of π or as a decimal.

Frequently asked questions

What is the formula for arc length?

Arc length = (θ ÷ 360°) × 2πr when θ is in degrees, or rθ when θ is in radians.

How do I find the area of a sector?

Sector area = (θ ÷ 360°) × πr², or ½r²θ in radians.

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MathMate can make mistakes. Please double-check important steps and calculations.