Vernier caliper: its parts, diagram, least count and how to read it with PDF

The Vernier Caliper most popular measuring instrument widely used in manufacturing industries, workshops, or metrology labs.

This is The Mechanical post and today we'll see about What is a Vernier Caliper? What are its parts? how to read it, least count of vernier, and a lot more.

Also, get your PDF copy of Vernier Caliper at the end of the article.

Vernier Caliper: its parts, least count and applications

What is a Vernier Caliper?

A Vernier caliper is an instrument used to measure linear dimensions, it consists of 2 scales (the main scale and vernier scale) and is used to measure the outside and inside diameter as well as the depth of a workpiece.

Vernier Caliper is used for making accurate measurements of a straight length between two points. It is based on the principle of “Difference between 2 scales”.

The tools like Vernier caliper & Screw gauge are more commonly used for precise and accurate measurements, with a small margin for error.

Vernier Caliper was introduced in 1631 by Pierre Vernier of France. {alertInfo}

What makes the vernier caliper so popular is that it can be used for measuring the depth, outside and inside diameter, length, width, and height of a workpiece just by using a single instrument. 

Vernier Caliper is a good choice when it comes to gifts for mechanical engineers.

Nowadays another version of the vernier caliper called the "Digital vernier caliper" is growing in popularity as they are extremely easy to use as well as they directly display the reading on the screen.

Parts of a Vernier Caliper

Vernier Caliper diagram

  • External jaws
  • Internal jaws
  • Depth probe
  • Thumb screw
  • Lock screw
  • Main scale
  • Vernier scale

External jaws

The external jaws of a vernier caliper are situated at the lower end. There are two jaws used within which the workpiece is held. 

Out of the two jaws, one is fixed while the other is movable. They are used to measure the external diameter of a workpiece.

Internal jaws

The internal jaws are at the upper end of the vernier caliper. These are used to measure the internal diameter of a workpiece.

Depth probe

The depth probe is a rod that slides back and forth when thumb screw is turned. As the name suggests, the depth rod is used to measure the depth of a workpiece.

Thumb screw

The thumbscrew is used to adjust the jaws as well as the depth probe of the vernier caliper as required.

Lock screw

The lock screw is used to lock the jaws so that the readings can be noted easily.

Main scale

The main scale of the vernier caliper is the scale that is marked onto the body of the vernier. It has markings in inches at the top and markings in millimeters at the bottom.

The value of 1 division on the Main scale on the mm side is 1mm.

Vernier Scale

The vernier scale is marked onto the body which slides parallel to the Main scale.

The scale has 50 divisions marked on it such that, the 50th division of the vernier scale coincides with the 49th division of the main scale.

This means that the 50 divisions of the Vernier scale are equal to 49mm on the Main scale.

Therefore the value of 1 division of vernier scale = 49 / 50 = 0.98mm

Least Count of Vernier Caliper

In simple words, the least count (or vernier reading) of a vernier caliper is the smallest distance that the caliper can measure.

The least count of vernier caliper is calculated as the difference between the value of 1 division of the Main scale and 1 division of the Vernier scale.

LC = 1M.S.R – 1 V.S.R

The value of 1 division on the main scale is 1mm whereas, the value of 1 division on the vernier scale is 0.98mm.

∴ LC = 1 - 0.98 = 0.02mm

∴ The Least count of Vernier Caliper is 0.02mm.

Another method to calculate the least count is by using this formula of Least Count:

L.C = (value of smallest division on main scale) / ( total no. of divisions on vernier scale )

   L.C = 1 / 50
∴ L.C = 0.02 mm

How to Read a Vernier Caliper?

Step 1

Calculate the least count (L.C) of the Vernier caliper. Then place the workpiece between the jaws and adjust it using the thumb screw.

Step 2

After firmly holding the workpiece between the jaws, note the reading on the main scale that is near zero marking of the Vernier scale.

Vernier Caliper diagram

Here in this case we’ll consider the reading shown above. The zero marking of the vernier scale is before 12mm and after 11mm. It means that the reading will be somewhere between 11mm & 12mm.

Since the zero marking is before 12, the reading will be in 11. something.

So in this case, the main scale reading (M.S.R) will be 11mm.

Step 3

Now, check the vernier scale. Look for the division that is coinciding with the main scale such that they appear as a straight line.

In this case, the 5th division is coinciding.

The Vernier Scale Division (V.S.D) will be 5.

Step 4

Calculate the Vernier Reading using the following formula.

Vernier Reading = M.S.R + (V.S.D * L.C)

= 11 + (5 * 0.02)

= 11.10mm

∴ The Vernier reading is 11.10 mm.

You might also like to read:

Vernier Caliper Range

The range (sometimes called maximum capacity) of a vernier caliper is the difference between the largest value and the smallest value that the caliper can measure. It is equal to the length of the main scale.

Most vernier calipers have a range of 6 inches (300mm), although calipers with smaller and larger ranges are also available. 

Applications of vernier caliper

  • Vernier caliper is widely used in workshops.
  • In manufacturing industries for inspection purposes. 
  • In Metrology labs for research.
  • They are also used in the aerospace industry.
  • Educational Institutions etc.

Image Credits:

Image no.1: Vernier Caliper Icons made by Freepik from

Image no. 2: Lucasbosch, CC BY-SA 3.0, via Wikimedia Commons

Image no.3: This figure is free to use with proper attribution & link to The Mechanical post

That's an overview of Vernier Caliper. If you like this post, do let us know about it in the comments we would love to hear from you. Till then keep learning!


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