Question: what is the formula to find the measure of an arc?
Answer: Arc Measure Formula Remember that the formula for arc measure is: s / r, or 4 / 5. Now, let's convert 4 / 5 radians to degrees by multiplying by 180 / pi. (4 / 5)(180 / pi) = 45.837, or approximately 46 degrees. As 46 degrees is about 1/8 of 360 degrees, the arc should be about 1/8 of a circle, as shown in our example.