How To Read A Vernier Caliper

vernier caliper

A quick guide on how to read a vernier caliper. A vernier caliper outputs measurement readings in centimetres (cm) and it is precise up to 2 decimal places (E.g. 1.23 cm).

Note: The measurement-reading technique described in this post will be similar for vernier calipers which output measurement readings in inches.

Measurement Reading Technique For Vernier Caliper

In order to read the measurement readings from vernier caliper properly, you need to remember two things before we start. For example, if a vernier caliper output a measurement reading of 2.13 cm, this means that:

  • The main scale contributes the main number(s) and one decimal place to the reading (E.g. 2.1 cm, whereby 2 is the main number and 0.1 is the one decimal place number)
  • The vernier scale contributes the second decimal place to the reading (E.g. 0.03 cm)
caliper 1

Let’s examine the image of the vernier caliper readings above. We will just use a two steps method to get the measurement reading from this:

  • To obtain the main scale reading: Look at the image above, 2.1 cm is to the immediate left of the zero on the vernier scale. Hence, the main scale reading is 2.1 cm
  • To obtain the vernier scale reading: Look at the image above and look closely for an alignment of the scale lines of the main scale and vernier scale. In the image above, the aligned line correspond to 3. Hence, the vernier scale reading is 0.03 cm.

In order to obtain the final measurement reading, we will add the main scale reading and vernier scale reading together. This will give 2.1 cm + 0.03 cm = 2.13 cm.

In a nutshell

Use the following formula:

$$ \text{Obtained reading} = \text{Main scale reading} \, + \, \text{Vernier scale reading} $$

Let’s go through another example to ensure that you understand the above steps:

caliper 2

Main scale reading: 10.0 cm (Immediate left of zero)

Vernier scale reading: 0.02 cm (Alignment of scale lines)

Measurement reading: 10.02 cm

Compensating For Zero Error

In a nutshell

Use the following formula:

$ \text{Correct reading} = \text{Obtained reading} \, – \, \text{Zero error} $

where $\text{zero error}$ can be either negative (the “0” of vernier scale is left of the “0” of the main scale) or positive (the “0” of vernier scale is right of the “0” of the main scale)


Now, we shall try with zero error. If you are not familiar on how to handle zero error for vernier calipers, I suggest that you read up on Measurement of Length.

caliper 3

The reading on the top is the measurement obtained and the reading at the bottom is the zero error. Find the actual measurement. (Meaning: get rid of the zero error in the measurement or take into account the zero error)

Measurement with zero error: 3.34 cm

Zero error: – 0.04 cm (negative because the vernier scale is to the left)

Measurement without zero error: $3.34 \, – ( \, – 0.04) = 3.38$ cm

If you do not understand the subtraction of the negative zero error from the measurement, please read on. Since the zero error is -0.04 cm, this means that all measurements taken by the vernier calipers will be SMALLER by 0.04cm. Hence, you will have to ADD 0.04 cm to ALL measurements in order to get the TRUE measurement. The subtraction is done in the above case is to have an elegant way of obtaining a resultant addition: $3.34 + 0.04 = 3.38$ and to make it COMPATIBLE with positive zero error. This means that once you have determined the nature of the zero error (positive or negative), you can just subtract the zero error and be sure that your final answer is correct.

Consider a zero error of +0.04 cm. With my method, $3.34 \, – (+ 0.04) = 3.30$ cm.

Normal method: Since the zero error is +0.04 cm, this means that all measurements taken by the vernier calipers will be larger by 0.04 cm. Hence, you will have to SUBTRACT 0.04 cm from ALL measurements in order to get the true measurement. The final calculation will be $3.34 \, – 0.04 = 3.30$ cm, which is the same as my method.

Note: I hope that I did not confuse you. Drop a comment below if you encounter any difficulties.

More Vernier Caliper Practice:

Self-Test Questions For Vernier Calipers

Where on the vernier calipers would you read to obtain the main scale reading?

Show/Hide Answer

The main scale reading is obtained from the reading on the main scale that is at the immediate left of the zero on the vernier scale.

Where on the vernier calipers would you read to obtain the vernier scale reading?

Show/Hide Answer

The vernier scale reading is obtained from the reading on the main scale that has an alignment of the scale lines of the main scale and vernier scale.

What is the smallest possible reading (in cm) of a vernier caliper?

Show/Hide Answer

The smallest possible reading of a vernier caliper is 0.01 cm.

If you still do not understand the concept, there is a very useful simulation of the vernier calipers: Vernier Caliper Simulation (Source)

Back To Measurement Of Physical Quantities (O Level)

Back To O Level Topic List

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208 thoughts on “How To Read A Vernier Caliper”

  1. First. You havenโ€™t explained what zero error is. That is specific to the instrument when closed. Nor do you explain how itโ€™s figured out. You showed a scale and and said itโ€™s .04. How?

  2. For the last diagram, since it is a negative zero error (as the 0 on the vernier scale is behind the 0 on the main scale), we imagine the numbers at the back of 0 on the main scale as -0.1, -0.2 and so on towards the left, and add the number shown on the vernier scale to the number on the left of the 0 on the vernier scale. In the diagram’s example, the main scale shows -0.1, and the vernier scale shows 0.06, therefore -0.1 + 0.06 is – 0.04, which is the zero error. It is NOT 0.06 as this is a negative zero error, not a positive one.

  3. I don’t understand why the scale on my gauge starts about 4mm from the left-hand jaw? So if I measure something, it gives a reading of say 5mm, but when I measure distance between jars with a tape measure, t’s actually 9mm?

  4. What’s about the different various vernier resolution e.g.
    0.02 mm
    0.05 mm
    imprinted on top of vernier moving part ?

    • It means that the measurement has an increment of 0.02 or 0.05. The lower the resolution, the higher the accuracy and precision.
      Let’s say the actual measurement is 4.57. If you use a caliper with a least count/resolution of 0.05, most probably your measurement reading will be 4.55. If you use a caliper with a 0.02 resolution, your measurement reading will be 4.56 OR 4.58 which is closer to the actual value.

  5. It tells that if it’s negative ,instead of reading it to left to right which is the answer will gonna be 0.06 cm, you need to read it right to left and start to 0.01, and the answer will 0.04. I hope you understand

  6. I appreciate the clear explanations on this site.

    However, I think there may be an error in the second figure under “Compensating for Zero Error.” To my reading, the error appears to be – 0.06 cm, not – 0.04 cm.

    Am I missing something?

  7. I was not clear about the topic but when I read this page, It was crystal clear to me. Thanks for being so helpful.

  8. In the illustration of the “zero error” measurement, the zero of the vernier scale appears to be slightly less that 1/2 way between the zero and the first hash mark of the main scale, but the alignment on the vernier scale seems to clearly occur on the “6”, making the zero measurement -0.06?

  9. See main scale is just immediately left to zero
    Vernier scale division is where two lines Aline
    Vernier scale reading is=vernier scale division into 0.01
    Total reading=vernier scale reading+main scale

    Itโ€™s very easy concept
    And this site really helped me

  10. After getting the vernier scale reading can I simply devide by 100 to get the actual reading. And if so, why is 100 chosen for this devision?

  11. Thanks very much, but i stil have a litle misundestanding on reading some scale, eg. from MS u start frnm the first figu

  12. can you fully showing out by arrows pointing directly to the readings of the scale on how you really get the measurement of the zero error ?

  13. Thanks for the excellent explanation including the part about the zero error which though very simple was never something that ever occurred to me.

    • For the vernier.
      When the zero mark on the vernier scale is to the left of the zero mark on the main scale,the error is negative.

      For the mic screw gauge.
      When the zero mark of the thimble scale is below the the horizontal line of the sleeve scale, the error is positive. Otherwise its negative.

  14. Thanks for this… I would like to clarify one thing: when you read the negative zero error, it seems that you are counting backwards from the right-most mark on the Vernier scale (four ticks) instead of forwards from the left (six ticks) on a normal measurement. Can you please confirm?

  15. Please like this question how can I solve it.

    A venier measures a distance of 1.17cm and the main scale reads 1.1cm . Draw and discover the venier scale reading

  16. I am a Physics teacher. Inexplicably, some of your answers seem wrong to me. Above, and in two of the practice examples (next page). Eg, above, the zero reading is -0.06, surely, not -0.04. What am I missing?

      • Hi ivan, i just wanted to ask that when you will stack up 20 pieces of paper and measure them with either vernier calliper or micrometer screw guage and get the reading and divide it with the number of pieces of paper you have taken measure of, will you read only the main scale or both scales on either both instruments

    • First look at the main scale and imagine additional lines to the left of zero, i.e. -0.1, -0.2, etc. Then if you read the caliper in the usual way, the Vernier scale zero lies to the right of the -0.1, so that is our “main scale” reading. Next you need to add the measurement from the Vernier scale, which as you mention is 0.06. This results in the “zero reading” in this case of -0.1 + 0.06 = -0.04.

      • Thank you, I was confused about this!
        Always read it on the mainscale as if it would have additional negative lines, and then add the value of the Vernier scale?
        With positive zero error the same way? So first main (fe. right to 0,1) and then vernier (fe. 0,06) = +0,16 ?

  17. Thanks so much! I needed this for my Physics exam and this really helped! Things were a bit unclear, but re-reading it solved it so it wasn’t that big of a deal

  18. The vernier reading (0.06) is a measure of the displacement of the vernier zero from the main scale marker to its immediate left, -0.1 . So the actual measurement at this point would be main plus vernier, -0.1 plus 0.06 equal to -0.04 if the error is less than one division to the left. Good luck.

  19. Thank you for this article..I decided to go and buy a newer type digital caliper as I found matching up the lines of the vernier sliding scale too hard on the eyes..and never felt exactly sure

    • Since the sliding scale 0 is left of the fixed scale 0 when the jaws are fully closed, you have to count from the right end of the sliding scale to the mark that most closely aligns with a mark on the fixed scale. In the example above, there are 4 marks from the right thus .04 is the correction. This is a negative error and must be subtracted from every reading taken. Subtracting a negative value is equivalent to adding. So, in the example, you would have to add .04 to every reading taken with this instrument.

    • When you deduct the vernier scale reading0.9ร—6=5.4mm from mains calendar reading 1ร—5=5mm you will get the error _0.4mm error

  20. I’ve a vernier scale whose reading on vernier scale is in double figures such as 25, 35… 75 etc. When I go to find out value of vernier scale, I get confused. Suppose my main scale value is 7mm, and my vernier scale shows 75mm, which after multiplying with 0.1 mm (L.C) leaves 7.5mm. Now to get final answer, I got to add 7 + 7.5 = 14.5 which is obviously the wrong answer in light of main scale’s reading. It should have been somewhere above 7 and below 8mm. How to figure this issue our? Should I take vernier’s value as .75mm instead of 75? If so, I left with 7.075 final answer whereas my other device shows 7.75.

    Any help?

  21. You are not confusing but a confused mind requires no stimulation to get more confused.

    But one suggestion is negative and positive symbols cld be shown and similarly the vernier scale should be highlighted and properly the reading should be marked with marker in order easily noticed.

  22. I don’t get how to calculate the zero error and subtract it… is there any simpler way to find the zero out? Also, you didn’t talk about positive and negative zero error.

  23. Thank you…. I found it most easiest explaination among all others but I have a confusion….. How the zero error is-0.04, according to what u taught here it should be – 0.06 as here the 6th smallest division on vernier scale lines up with maine scale division.

    Thank u

    • If the zero division of M.S is on the left side of zero division of V.S then it is ve zero error and if on the right hand side then -ve error

  24. This method is really helpful and comparatively easier. However, i have one concern; if all the readings are in mm the same 0.0x reading will be taken for vernier caliper?
    Please reply as soon as possible. ๐Ÿ™‚

  25. Nice and very helpful information for assignment. But it would have been great if you have embedded video to describe process of reading vernier caliper.

  26. A It is good tutorial, but aimed at students in USA only. In some old systems , which are in vogue at some places , an inch is divided in 8 parts and fractions like 1/8, 1/16, 1/32 and so on. how does a vernier work in those system ? A passing remark, I believe, would be desirable.

    • The basic structure and instructions to read the vernier caliper divided in inches are the same for a vernier caliper divided in cm (as above).

      For a vernier caliper whose vernier scale is divided in fractions of an inch ($\frac{1}{8}$, $\frac{1}{16}$, …), the instructions to read the vernier caliper is the same! Consider the image below:

      In this image, we are interested in the scale at the top. The reading given by the main scale is 0.75 inches.

      The vernier scale is divided into $\frac{1}{128}$ inches. This means that each division is 0.0078125 inches ($\frac{1}{128}$). The reading given by the vernier scale is 1 division on a $\frac{1}{128}$ inches scale, which gives approximately 0.008 inches. Hence, the reading is 0.758 inches.

  27. This very helpful. Thanks a lot.
    Only one thing i did not understand how did u get the zero error to be + 0.04
    i get the concept of positive and negative zero error but how did u read 0.04.

    • In the diagram, the marking denoting ‘6’ matches with the main scale. The reading is 0.06 cm. However, since the vernier scale is to the left of the main scale, this means that ALL readings are short by 0.1 – 0.06 = 0.04 cm.

      You subtract the 0.06 cm because you only need to shift 0.04 cm to the right to get the “perfect” vernier caliper (one with no zero error). Hence, 0.04 cm is the error.

  28. That was not confusing at all. Thanks for the help, i was actually struggling with zero error and could not find any reference in text books or even other websites. This really cleared all my questions. Thanks again.


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