Micrometer Least Count – Full Details Here

It is very easy to calculate Micrometer Least Count, if you are looking for its formula and other details about the micrometer screw gauge then read this article till the end.

It is very crucial to know the least count of such instruments as they help us in taking accurate readings during various experiments.

Do you know what is the definition of least count and why it is required? It is calculated as the smallest change in the measured quantity that can be resolved on its scale. Keep reading to know the micrometer least count formula and how it helps in our experiments.

What actually is a Micrometer?

A micrometer which is sometimes referred to as a screw gauge is a measuring device that operates on the screw principle. When you rotate the screw, the spindle moves back and forth precisely to measure the piece.

This instrument is used in various labs and widely used in mechanical engineering to measure wire diameters, workpiece thickness, and many other things.

Parts of micrometer:

Before sharing the micrometer least count formula, you should know about the parts of the micrometer so the details are given below:


It is attached to the right side of the frame and the spindle within it moves back and forth, it indicates the main scale or the linear scale.

Nut for locking

It prevents the spindle from turning, this feature comes in handy when taking measurements. It helps in avoiding errors by keeping the scale in a fixed position when taking readings.


It is used to make fine adjustments and helps in avoiding overtightening when measuring a workpiece, ensuring that equal pressure is applied by the spindle during measurement.


It is attached to the sleeve and has the circular scale written on it, the spindle can be moved to and fro by rotating the thimble.


It has external screw threads that allow it to move back and forth with precision. The spindle thread typically has a pitch of 0.5mm or 1mm.


A small fixed part on the frame’s left side is an anvil and its face is parallel to the spindle’s face. It comes into contact with the workpiece, which is why it is machined to achieve a high surface finish for improved precision.


The C-shaped metal part of the micrometer or screw gauge is a frame. It holds up the anvil on the left and the sleeve and spindle on the right.

What is Micrometer Least Count?

The Least Count of the micrometer screw gauge is 0.01mm or 0.0001cm which can be calculated by the formula given below:

Least Count (L.C.) = Minimum Main scale division / Total circular scale divisions.

The minimum main scale division value of the micrometer is 0.5 mm, and a circular scale is divided into 50 lines. Now, by putting these values in the formula given above, we can get the least count of a micrometer. The calculation is shown below:

Micrometer Least Count = 0.5 / 50 = 0.01 mm or 0.0001cm.

If you want to have accurate results then make sure to check the micrometer before taking the reading for any positive or negative zero errors.

You have to re-calibrate the instrument if you found any error. Furthermore, you have to use the ratchet to obtain accurate measurements and avoid rotating the circular scale directly.

Types of Error in Micrometer:

Micrometer Least Count helps in calculating the two types of errors you could face when using the micrometer or screw gauge in your experiment. Read below to learn about them:

Positive zero error:

Check if the ‘0’ marking on the circular scale is below the main scale line when the anvil and spindle are brought together, then it is referred to as “Positive zero error.”

You must multiply the Micrometer Least Count with the circular scale reading and use the +ve sign with your answer. Now, correct your reading from the formula given below:

Corrected reading = Observed reading – Zero error

Negative zero error:

When the anvil and spindle are brought together in a manner that their faces touch together, and the ‘0’ marking on the circular scale is above the main scale line, then it is known as “Negative zero error.”

You must multiply the Micrometer Least Count with the circular scale reading and use the –ve sign with your answer. Now, correct your reading from the formula given below:

Corrected reading = Observed reading – Zero error

Wrapping Up:

We hope you can get accurate results from your experiments now that you know Micrometer Least Count and how to calculate it. Please leave a comment below to share your thoughts on this article.

Read more interesting articles at Deep Tech Discovery

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