**1.**Evaluating the measure of volume with respect to time provides the rate of flow of the given volume.

**2.**2nd is the distance moved in a particular time, which is known as velocity of the flow.

Mostly these parameters are dependent upon the diameter of the pipe whether it is small or large. Using these two measures we can evaluate the diameter of the pipe. Let us see how to measure pipe diameter with help of an example:

To start with, 1st find out the product of velocity and mathematical quantity pi i.e. 3.14. Suppose the velocity of flow is given as 40 mm / sec, then multiplying it with 3.14 we get: 125.6 mm /sec.

Next we multiply the rate of flow by 4. In our example suppose the flow rate is 200 cubic mm per second, then we would get the product as: 200 mm3 /sec x 4 = 800 mm³ /sec.

Next step is to divide the result that was evaluated in the previous step by the result of 1st step. In our example we would get: 800 mm3 per sec /125.6 mm per sec = 6.3694 mm². mm per sec is canceled out in the calculation.

Lastly we evaluate the Square root of the result i.e. 6.3694 mm2 from 3rd Step. In our example we get 2.523 as square root of 6.3694. Thus diameter of the pipe is 2.523 mm. Square root is taken over the unit also.