Tangential speed measures how quickly an object going in a circle is traveling. The formula calculates the total distance the object travels and then finds the speed based on how long it takes the object to travel that distance. If two objects take the same amount of time to complete a revolution, the object traveling in the circle with the greater radius will have the faster tangential speed. A larger radius means the object travels a greater distance.

Multiply the radius by 2 to find the diameter of the circle. The radius is the distance from the center of the circle to the edge. For example, if the radius equals 3 feet, multiply 3 by 2 to get a diameter of 6 feet.

Multiply the diameter by pi -- which is 3.14 -- to find the the circumference. In this example, multiply 6 by 3.14 to get 18.84 feet.

Divide the circumference by the amount of time it takes to complete one rotation to find the tangential speed. For example, if it takes 12 seconds to complete one rotation, divide 18.84 by 12 to find the tangential velocity equals 1.57 feet per second.