Enter a radius and central angle to calculate the arc length.
How to Use the Arc Length Calculator
Enter a radius and the central angle in degrees. The arc length updates immediately.
arc length = (angle ÷ 360°) × 2π × radiusAn arc is just a fraction of the full circumference — a 90° arc is exactly a quarter of the way around, a 180° arc exactly half, no matter how big the circle is. That proportionality is also the definition behind radian measure: an angle of exactly 1 radian marks off an arc exactly one radius long.