Arc length is the distance along the arc/curve,^[1] denoted by "S", the target arc can be denoted by"L" or "${\displaystyle {\overset {\frown }{MN}}}$", not the distance between its endpoints, which is known as the chord length and is denoted by "C".

Not all curves can be defining length, curves that can be defined by the length are called the rectifiable curves.^[2]

Depending on the given, there are two different ways to find the Arc Length.^[3]

Arc length on a circle can be measured as Arc length = s = θ/360 of 2πr = θ/360 × 2πr = rθ × π/180. (θ represents the degree of the Center angle,"r" represents the Radius of the circle).

Arc length on a circle can be measured as Arc length= s = r × θ

The original method for calculating the arc length involves dividing the arc into many parts to obtain an estimated answer:

1. The curve is divided into smaller segments, and the length of each segment can be calculated by the Pythagorean theorem or other methods.
2. The total length of the curve can be obtained by summing each part.