Mechanical Basics

What is Vernier Calipers?

Vernier Calipers is one of the Precision Instruments used to find Distance, External Diameter, Internal Diameter, and Depths or Heights of any component that normal instruments cannot. The size of the Vernier Calipers depends upon the application. The least count of Vernier Caliper is the main reason for its application in manufacturing industries and quality control rooms. Moreover can find different sizes of Vernier Calipers according to the work piece or job that need to inspect and machine tool where the job is machined.

What is Vernier Calipers, How to Measure with Vernier Caliper, and Applications

As it is mentioned, the vernier calipers is used to find external diameter, internal diameter, and  depths, so it must consist different parts or scales which we call as Vernier Scale, and Main Scale. Accordingly, it consists references like Internal Jaws, External Jaws to measure diameter, depths, etc. Pierre Vernier is the inventor of the Vernier Calipers. He is a French Instrument Inventor and mathematician.

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What is Least Count of Vernier Caliper?

The least count is the minimum count or value that a measuring device can be used to measure. Every measuring instrument does consist of the least count and the least count of the vernier calipers is 0.02 millimeter and 0.002 centimeter. It means the vernier calipers can measure a component of size 0.02 millimeter or 0.002 centimeter.

Vernier Caliper Least Count Formula:

A Vernier consists of Main Scale, and a Vernier Scale that can able to slide on the Scale and addition to the scales, the vernier does consists 

1. Outer Jaws or External Jaws

2. Inner or Internal Jaws, and 

3. Screw Clamp (that is used to tighten the Vernier Scale against Main Scale)

The vernier caliper least count formula is the “difference between 1 Main Scale Division (M.S.D) and 1 Vernier Scale Division (V.S.D)”. The main scale consists of 49 divisions and each division is 1 mm the length and the vernier scale consists of 50 divisions, and each division is 49/50 = 0.98 mm.

Now, the least count of vernier caliper = 1 M.S.D – 1 V.S.D

                                                                            = 1 mm – 0.98 mm

                                                                        = 0.02 millimeter

So, after computing the values with the help of formula for Least Count of Vernier Caliper, the least count of vernier caliper is 0.02 millimeter.

How to measure diameter using Vernier Caliper?

Let us take a ball and as it is a sphere we can find only the outer diameter of it.

What is Vernier Calipers, How to Measure with Vernier Caliper, and Applications

We can observe the Outer or External jaws in the Vernier Calipers, the component that is used to measure the diameter should place between these two jaws. As we are taking the sphere ball so, the sphere ball should be placed between the below jaws and observe the main scale readings. If the vernier scale starting division is crossed 21st division on the Main scale then note down 21 as Main scale reading.

Now, if we cleanly observe the Index lines of the Vernier Scale, even one division will coincide with the Index line of Main Scale then note the coincided division as Vernier Reading.

Now the formula to find the diameter of the component is 

Main Scale Reading + (Vernier Scale Reading * Least Count)

Then 21 + (23 * 0.02) = 21.46 mm. Then the diameter of the component is 21.46 mm.

How to measure internal diameter using Vernier Caliper?

So we can see the Inner jaws on the top of the the Vernier Calipers, we will measure the internal diameter by using those jaws. Firstly, we have to insert those jaws into the hole of the component then tighten the Clamp to avoid the play; then observe the readings on the scales and follow the same procedure as we used to find the external diameter above to calculate it.

How to measure the Depths?

What is Vernier Calipers, How to Measure with Vernier Caliper, and Applications

Let us take a small Hallow cylinder that should be open at one end and closed at another end (Example: Drum) so, to find the depth of the inner hole we cannot use normal Instruments like Scale to get an accurate measurement. To find the accurate measurements, the vernier will be helpful.

We can observe a Tail type part called Stem in the Vernier. Now loose the Clamp and allow as much depth as the Stem could come then invert it into the hole and observe the values on both the scales and follow the procedure that we used to find the diameter of the sphere ball.

Advantages of Vernier Caliper:

The advantages of vernier Caliper are as follows:

  • Vernier Calipers is used to measure the external diameter and the internal diameters too.
  • The vernier calipers help to find the heights and depths of the components.
  • Vernier Calipers can measure the component up to 0.02 mm and 0.002 cm, which we called as the least count of vernier caliper.
  • Vernier Calipers is accurate and easy to method the measurements.
  • We can find small and large verniers according to the applications.

Applications of Vernier Caliper:

The applications of the vernier calipers are vast and necessary. They are

  • Vernier Calipers is used in quality checking, tool rooms, and machine tools for accurate productions.
  • Vernier Calipers can be useful in pharmaceutical labs.
  • Vernier Calipers is used to check the Run-outs of Shafts.
  • Vernier Calipers is used in all manufacturing companies to maintain perfect measurements.


The Vernier Calipers is one of the important measuring instrument in the mechanical world, we cannot proceed further in mechanical work life without the knowledge of vernier. Vernier Calipers are mostly used by the machine tool operators for checking the dimensions of the cutting parts. As it is accurate and can measure even 0.02 millimeter, it is sensitive and need to store carefully. Even the temperature differences will affect the Vernier Calipers.  v

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