Arc Length (Radians) Calculator

Arc length from a radius and a radian angle.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

When an angle is measured in radians, arc length reduces to a one-line formula: s = r × θ, because a radian is defined as the angle that subtends an arc equal in length to the radius — no conversion factor or π needed, unlike the degree version which requires s = r × θ × π/180.

This direct relationship is why engineers, machinists, and physics students prefer working in radians for anything involving rotation or circular motion — gear tooth spacing, pulley belt lengths, satellite orbital paths, and pendulum swing distances are all sized with this exact formula.

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