Reading vernier caliper takes more steps than reading dial caliper or reading digital caliper. The users have to manually calculate both the scales (the main scale and the vernier scale). Vernier scale calculation, especially, is the contrasting thing when compared to reading those two types of caliper.
Your eyes have to be careful when deciding which one the aligned line is. This is the core thing when you read vernier caliper. It requires good eyesight. If you fail to do that, your measurement will be incorrect.
In many cases, you can see our list of recommended vernier calipers, a single vernier caliper commonly provides inch and mm graduation. That means you can get two versions of readout whether in mm or inch. But, some products can also come with either mm or inch graduation only.
If you see on the market, the inch reading models provide a resolution down to 0.001″ or 1/128″ (imperial unit). On the other hand, the metric models provide a resolution down to 0.02 mm, 0.05 mm, or 0.1 mm (metric unit). The variation of these resolutions leads to different graduation systems. Even further, among the same resolution, the graduation system can be different as well.
In this post, we will be discussing how to read vernier caliper that has those kinds of graduation systems. Whether it is in mm (millimeter) or inch, we will be covering it here. Through this post, you’ll know the graduation variation systems that we mean. Before you go further, you have to learn first what the general formula is and how to read the zero error.
The General Formula
Basically, the thumb rule in reading vernier caliper is similar both for the inch and mm scale.
Final Result = Main Scale Reading + Vernier Scale Reading – Zero Error
The main scale reading is the amount of the vernier scale divisions that are completely passed by the vernier scale’s zero line. While the vernier scale reading is the amount of vernier scale divisions from 0 to the aligned line.
You could see the following picture. The first (left) yellowed line shows how many divisions passed by the vernier 0 marking. In this case, it has passed 42 divisions. While the second (right) yellowed line shows the aligned line.
Therefore, the main scale reading depends on the vernier scale, while the vernier scale reading depends on the aligned line. What is the aligned line? Whenever you slide the vernier scale, there must be two lines (one from the main scale and one from the vernier scale) that completely shape a united straight line.
The vernier scale functions to divide the smallest division of the main scale into a particular amount of divisions so that it generates the desired resolution.
If the main scale has 40 divisions per inch, it means each smallest division on the main scale has a value of 0.025″.
Smallest main scale division’s value = 1″ : 40 divisions = 0.025″
To generate a 0.001″ resolution, the vernier scale has to provide 25 divisions. That’s because the smallest main scale division divided by 25 is 0.001″.
Smallest vernier scale division’s value = 0.025″ : 25 divisions = 0.001″
Further, the calculation of the main and vernier reading takes zero error into account although in most cases, the zero error is “0” and you can avoid it.
What is Zero Error?
Prior to reading the vernier caliper, you need to check whether the zero error exists or not. If it appears, you have to figure it out when calculating/reading the final measurement. Keep measuring without taking the zero error into calculation, you are measuring in an incorrect way.
Zero error is the condition where the zero markings of both scales (main scale and vernier scale) don’t shape an aligned line. It happens when you close both the two jaws (fixed and movable jaw) properly.
There are 3 possibilities that may happen: no zero error, negative zero error, and positive zero error.
- Negative zero error is when the vernier scale’s zero marking lies at the left side of the main scale’s zero markings.
- Positive zero error is when the vernier scale’s zero marking lies at the right side of the main scale’s zero marking.
- No zero error means it’s completely an aligned line.
If you find a misalignment (either positive or negative zero error), you have to include it in the calculation of the final measurement.
How to Read Vernier Caliper’s Zero Error
Basically, to read the zero error is the same as to read the vernier caliper as usual. It takes both the main and vernier scales to measure. However, it can be confusing when you are facing a negative zero error. Fortunately, by creating an imaginary additional scale like the following image, you can start putting the measurement in a fixed formula.
The first step that you have to do is to define the value of each smallest division for both the main and vernier scale. Decide whether the scale is imperial (inches) or metric (mm). In this case, the above scale is inches. By looking at the graduation, we know that the main scale has 20 divisions per inch and the vernier scale has 50 divisions. Then,
Main scale value / division = 1 inch : 20 divisions = 0.05″/division
Vernier scale value / division = 0.05″ : 50 divisions = 0.001″/division
The second step is to count the main and the vernier scale, then add them altogether.
Main scale = −1 × 0.05″/division = −0.05″
Vernier scale = 47 × 0.001″/division = 0.047″
Negative zero error = −0.050″ + 0.047″ = −0.003″
Actually, there is a shorter way of reading the zero error. But we just want to make sure that you know this basic measurement before jumping into the shortcut method.
The shorter way is by reading in reverse. If you find the vernier scale graduated from left to right. You can imagine that the increment ( 0 to 50) is graduated from right to left. Just directly measure zero error from the 0 markings of the vernier scale, and you will get the answer. But, this method works only when the zero error is less than the smallest main scale division value.
How to Read Vernier Caliper in mm (Metric)
When it comes to metric vernier caliper, there are several resolutions available: 0.02 mm, 0.05 mm, and 0.1 mm. Different resolution has different graduation model. Soon, you will know the graduation models that we mean and how to read them.
We name them as model 1 (0.02 mm resolution), model 2 (0.05 resolution), and model 3 (0.1 mm resolution). Among these models, model 1 is the most used and easily found on the market.
1. Reading Vernier Caliper Model 1 (0.02 mm Resolution)
This model has 10 divisions per cm on its main scale and 50 divisions on its vernier scale. Example of vernier caliper that comes with this graduation model is Mitutoyo 532-119 vernier caliper.
See the following image when this graduation model shows no zero error.
Therefore, the smallest reading on the main scale:
1 cm : 10 divisions = 1 mm
And the smallest reading on the vernier scale:
1 mm : 50 divisions = 0.02 mm
Reading Metric Vernier Caliper Model 1 Case 1 (With No Zero Error)
Main scale = 10 × 1 mm = 10 mm
Vernier scale = 3 × 0.02 mm = 0.06 mm
Zero error = 0 mm
Final reading = 10 mm + 0.06 mm − 0 mm = 10.06 mm
Reading Metric Vernier Caliper Model 1 Case 2 (With Negative Zero Error)
Main scale = −1 × 1 mm = −1 mm
Vernier Scale = 47 × 0.02 mm = 0.94 mm
Zero error = −1 mm + 0.94 mm = −0.06 mm
Main scale = 12 × 1 mm = 12 mm
Vernier scale = 13 × 0.02 mm = 0.26 mm
Zero error = −0.06 mm
Final reading = 12 mm + 0.26 mm − (−0.06 mm) = 12.32 mm
Reading Metric Vernier Caliper Model 1 Case 3 (With Positive Zero Error)
Main scale = 0 × 1 mm = 0 mm
Vernier scale = 3 × 0.02 mm = 0.06
Zero error = 0 mm + 0.06 mm = 0.06 mm
Main scale = 18 × 1 mm = 18 mm
Vernier scale = 37 × 0.02 mm = 0.74 mm
Zero error = 0.06 mm
Final reading = 18 mm + 0.74 mm − 0.06 mm = 18.68 mm
Reading Metric Vernier Caliper Model 1 Case 4 (With No Zero Error)
Main scale = 18 × 1 mm = 18 mm
Vernier scale = 45 × 0.02 mm = 0.9 mm
Zero error = 0 mm
Final reading = 18 mm + 0.9 mm − 0 mm = 18.9 mm
2. Reading Vernier Caliper Model 2 (0.05 mm Resolution)
This model has 10 divisions per cm on its main scale and 20 divisions on its vernier scale. Example of vernier caliper that comes with this graduation model is Mitutoyo 531-128.
See the following image when this graduation model shows no zero error.
The smallest reading on the main scale is
1 cm : 10 divisions = 1 mm
The smallest reading on the vernier scale is
1 mm : 20 divisions = 0.05 mm
Reading Metric Vernier Caliper Model 2 Case 1 (With No Zero Error)
Main scale = 10 × 1 mm = 10 mm
Vernier scale = 3 × 0.05 mm = 0.15 mm
Zero error = 0 mm
Final reading = 10 mm + 0.15 mm − 0 mm = 10.15 mm
Reading Metric Vernier Caliper Model 2 Case 2 (With Negative Zero Error)
Main scale = −1 × 1 mm = −1 mm
Vernier Scale = 17 × 0.05 mm = 0.85 mm
Zero error = −1 mm + 0.85 mm = −0.15 mm
Main scale = 13 × 1 mm = 13 mm
Vernier scale = 7 × 0.05 mm = 0.35 mm
Zero error = −0.15 mm
Final reading = 13 mm + 0.35 mm − (−0.15 mm) = 13.35 mm + 0.15 mm = 13.50 mm
Reading Metric Vernier Caliper Model 2 Case 3 (With Positive Zero Error)
Main scale = 0 × 1 mm = 0 mm
Vernier Scale = 3 × 0.05 mm = 0.15 mm
Zero error = 0 mm + 0.15 mm = 0.15 mm
Main scale = 18 × 1 mm = 18 mm
Vernier scale = 19 × 0.05 mm = 0.95 mm
Zero error = 0.15 mm
Final reading = 18 mm + 0.95 mm − 0.15 mm = 18.80 mm
3. Reading Vernier Caliper Model 3 (0.1 mm Resolution)
This model has 10 divisions per cm on its main scale and 10 divisions on its vernier scale. Examples of vernier caliper that come with this graduation model are EISCO PH0078B and Vikye.
See the following image when this graduation model shows no zero error.
The smallest reading of the main scale is:
1 cm : 10 divisions = 1 mm
The smallest reading of the vernier scale is
1 mm : 10 divisions = 0.1 mm
Reading Metric Vernier Caliper Model 3 Case 1 (With No Zero Error)
Main scale = 12 × 1 mm = 12 mm
Vernier scale = 5 × 0.1 mm = 0.5 mm
Zero error = 0 mm
Final reading = 12 mm + 0.5 mm − 0 mm = 12.5 mm
Reading Metric Vernier Caliper Model 3 Case 2 (With Negative Zero Error)
Main scale = −1 × 1 mm = −1 mm
Vernier Scale = 7 × 0.1 mm = 0.7 mm
Zero error = −1 mm + 0.7 mm = −0.3 mm
Main scale = 19 × 1 mm = 19 mm
Vernier scale = 9 × 0.1 = 0.9 mm
Zero error = −0.3 mm
Final reading = 19 mm + 0.9 mm − (−0.3 mm) = 20.2 mm
Reading Metric Vernier Caliper Model 3 Case 3 (With Positive Zero Error)
Main scale = 0 × 1 mm = 0 mm
Vernier Scale = 3 × 0.1 mm = 0.3 mm
Zero error = 0 mm + 0.3 mm = 0.3 mm
Main scale = 10 × 1 mm = 10 mm
Vernier scale = 3 × 0.1 mm = 0.3 mm
Zero error = 0.3 mm
Final reading = 10 mm + 0.3 mm − 0.3 mm = 10 mm
How to Read Vernier Caliper in inches (Imperial)
The imperial (inch) vernier calipers may come in decimal or fractional resolution. The decimal resolution is commonly 0.001″, while the fractional resolution is commonly 1/128″.
However, the decimal resolution models vary in terms of graduation models. Some of them have the main scale graduated with 50 divisions per inch, and the vernier scale graduated with 20 divisions. Another model has the main scale graduated with 40 divisions per inch while the vernier scale graduated with 25 divisions. And another decimal model has the main scale graduated with 20 divisions per inch while the vernier scale graduated with 50 divisions.
1. Reading Imperial Vernier Caliper Model 1 (0.001″ Resolution)
This model has 50 divisions per inch on its main scale and 20 divisions on its vernier scale. Example of vernier caliper that comes with this graduation model is Starrett 456AZ.
See the following image when this graduation model shows no zero error.
The smallest reading of the main scale is
1″ : 50 divisions = 0.02″
The smallest reading of the vernier scale is
0.02″ : 20 divisions = 0.001″
Reading Imperial Vernier Caliper Model 1 Case 1 (With No Zero Error)
Main scale = 50 × 0.02″ = 1″
Vernier scale = 3 × 0.001″ = 0.003″
Zero error = 0″
Final reading = 1″ + 0.003″ − 0″ = 1.003″
Reading Imperial Vernier Caliper Model 1 Case 2 (With Negative Zero Error)
Main scale = −1 × 0.02″ = −0.02″
Vernier scale = 17 × 0.001″ = 0.017″
Zero error = −0.020″ + 0.017″ = −0.003″
Main scale = 56 × 0.02″ = 1.12″
Vernier scale = 17 × 0.001″ = 0.017″
Zero error = −0.003″
Final reading = 1.12″ + 0.017″ − (−0.003″) = 1.137″ + 0.003″ = 1.140″
Reading Imperial Vernier Caliper Model 1 Case 3 (With Positive Zero Error)
Main scale = 0 × 0.02″ = 0″
Vernier scale = 3 × 0.001″ = 0.003″
Zero error = 0″ + 0.003″ = 0.003″
Main scale = 56 × 0.02″ = 1.12″
Vernier scale = 5 × 0.001″ = 0.005″
Zero error = 0.003″
Final reading = 1.12″ + 0.005″ − 0.003″ = 1.122″
2. Reading Imperial Vernier Caliper Model 2 (0.001″ Resolution)
This model has 40 divisions per inch on its main scale and 25 divisions on its vernier scale. Example of vernier caliper that comes with this graduation model is Mitutoyo 532-119.
See the following image when this graduation model shows no zero error.
The smallest reading of the main scale is
1″ : 40 divisions = 0.025″
The smallest reading of the vernier scale is
0.025″ : 25 divisions = 0.001″
Reading Imperial Vernier Caliper Model 2 Case 1 (With No Zero Error)
Main scale = 40 × 0.025″ = 1″
Vernier scale = 3 × 0.001″ = 0.003″
Zero error = 0″
Final reading = 1″ + 0.003″ − 0″ = 1.003″
Reading Imperial Vernier Caliper Model 2 Case 2 (With Negative Zero Error)
Main scale = −1 × 0.025″ = −0.025″
Vernier scale = 22 × 0.001″ = 0.022″
Zero error = −0.025″ + 0.022″ = −0.003″
Main scale = 51 × 0.025″ = 1.275″
Vernier scale = 0 × 0.001″ = 0″
Zero error = −0.003″
Final reading = 1.275″ + 0″ − (−0.003″) = 1.275″ + 0.003″ = 1.278″
Reading Imperial Vernier Caliper Model 2 Case 3 (With Positive Zero Error)
Main scale = 0 × 0.025″ = 0″
Vernie scale = 3 × 0.001″ = 0.003″
Zero error = 0″ + 0.003″ = 0.003″
Main scale = (17 × 4) × 0.025″ = 1.7″
Vernier scale = 10 × 0.001″ = 0.010″
Zero error = 0.003″
Final reading = 1.7″ + 0.010″ − 0.003″ = 1.710″ − 0.003″ = 1.707″
Reading Imperial Vernier Caliper Model 2 Case 4 (With No Zero Error)
Main scale = (19 × 4) × 0.025″ = 1.9″
Vernier scale = 10 × 0.001″ = 0.010″
Zero error = 0″
Final reading = 1.9″ + 0.010″ − 0″ = 1.910″
3. Reading Imperial Vernier Caliper Model 3 (0.001″ Resolution)
This model has 20 divisions per inch on its main scale and 50 divisions on its vernier scale. Example of vernier caliper that comes with this graduation model is Mitutoyo 534-117.
See the following image when this graduation model shows no zero error.
The smallest reading of the main scale is
1″ : 20 divisions = 0.05″
The smallest reading of the vernier scale is
0.05″ : 50 divisions = 0.001″
Reading Imperial Vernier Caliper Model 3 Case 1 (With No Zero Error)
Main scale = 20 × 0.05″ = 1″
Vernier scale = 3 × 0.001″ = 0.003″
Zero error = 0″
Final reading = 1″ + 0.003″ − 0″ = 1.003″
Reading Imperial Vernier Caliper Model 3 Case 2 (With Negative Zero Error)
Main scale = −1 × 0.05″ = −0.05″
Vernier scale = 47 × 0.001″ = 0.047″
Zero error = −0.050″ + 0.047″ = −0.003″
Main scale = 19 × 0.05″ = 0.95″
Vernier scale = 49 × 0.001″ = 0.049″
Zero error = −0.003″
Final reading = 0.95″ + 0.049″ − (−0.003″) = 0.999″ + 0.003″ = 1.002″
Reading Imperial Vernier Caliper Model 3 Case 3 (With Positive Zero Error)
Main scale = −0 × 0.05″ = 0″
Vernier scale = 3 × 0.001″ = 0.003″
Zero error = 0″ + 0.003″ = 0.003″
Main scale = 18 × 0.05″ = 0.9″
Vernier scale = 39 × 0.001″ = 0.039″
Zero error = 0.003″
Final reading = 0.9″ + 0.039″ − 0.003″ = 0.939″ − 0.003″ = 0.936″
4. Reading Imperial Vernier Caliper Model 4 (1/128″ Resolution)
This model has 16 divisions per inch on its main scale and 8 divisions on its vernier scale. Example of vernier caliper that comes with this graduation model is Mitutoyo 531-128.
See the following image when this graduation model shows no zero error.
The smallest reading of the main scale is
1″ : 16 divisions = 1/16″
The smallest reading of the vernier scale is
1/16″ : 8 divisions = 1/128″
Reading Imperial Vernier Caliper Model 4 Case 1 (With No Zero Error)
Main scale = 16 × 1/16″ = 1″
Vernier scale = 3 × 1/128″ = 3/128″
Zero error = 0″
Final reading = 1″ + 3/128″ − 0″ = 1 3/128″
Reading Imperial Vernier Caliper Model 4 Case 2 (With Negative Zero Error)
Main scale = −1 × 1/16″ = −1/16″
Vernier scale = 7 × 1/128″ = 7/128″
Zero error = −8/128 + 7/128″ = −1/128″
Main scale = 14 × 1/16″ = 14/16″ (7/8″)
Vernier scale = 7 × 1/128″ = 7/128″
Zero error = −1/128″
Final reading = 14/16″ + 7/128″ − (−1/128″) = 112/128″ + 7/128″ + 1/128″ = 120/128″ (15/16″)
Reading Imperial Vernier Caliper Model 4 Case 3 (With Positive Zero Error)
Main scale = 0 × 1/16″ = 0″
Vernier scale = 1 × 1/128″ = 1/128″
Zero error = 0″ + 1/128″ = 1/128″
Main scale = 8 × 1/16″ = 8/16″ (1/2″)
Vernier scale = 2 × 1/128″ = 2/128″
Zero error = 1/128″
Final reading = 8/16″ + 2/128″ − 1/128″ = 64/128″ + 2/128″ − 1/128″ = 65/128″
Reading Imperial Vernier Caliper Model 4 Case 4 (With No Zero Error)
Main scale = 30 × 1/16″ = 30/16″ = 1 14/16″
Vernier scale = 3 × 1/128″ = 3/128″
Zero error = 0″
Final reading = 1 14/16″ + 3/128″ − 0″ = 1 112/128″ + 3/128″ = 1 115/128″
Conclusion
Learning how to read vernier caliper benefits you to accomplish before using it. Unlike digital caliper or dial caliper that is relatively easier to read, reading vernier caliper takes more effort to be familiar with.
Aside from that benefit, learning how to read the vernier caliper means you are learning to read the vernier scale. This scale can be found in several linear measuring instruments such as vernier micrometer, vernier depth gauge, etc.
In short, the opening step that you have to do is to ensure the value of the smallest division of the main scale and the vernier scale. Then, you have to check the zero error. If the zero marking is not aligned, you have to measure the value. Then, read the main and vernier scale. Finally, add the reading of the main scale, vernier scale, and zero error altogether. The result of these three readings is the final reading.
Actually, when you calibrate the vernier caliper, you are doing measurement and calculation surely, you have to add the uncertainty value. However, since this topic only covers how to read vernier caliper as a general method (not for calibration), we don’t take uncertainty into the calculation.
