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The calibrator, also known as vernier or vernier caliper, is one of the most used tools in workshops for the measurement of various objects, as well as to verify that the measurement is correct. There are different models and sizes of this tool, there are also vernier instruments with different resolutions for example 5 hundredths, 2 hundredths and with the advance of technology we can find digital vernier. The vernier consists of a pair of rules, a fixed and a mobile sliding, the common gauge allows measuring external dimensions, interior and depth of objects. The mobile rule or vernier has the marked divisions covering nine divisions for the fixed or main rule, so that this correspond to 9/10 of a division of the main rule.


Depending on the Vernier you can vary the parts you have, the fixed tip and moving tip correspond to the jaws for internal measurements, the fixed leg and movable leg corresponds to the jaws for external measurements.

  • Outside jaw: Corresponds to the clamp to measure the exterior of the desired piece.
  • Outside mobile jaw : It corresponds to the clamp to measure the exterior of the pieces, it allows to adjust the measuring surface due to the sliding that it has.
  • Inside jaw: Part of the clamp to internally measure the desired part.
  • Inside mobile jaw: Part of the clamp to measure the interior of the pieces, allows to adjust the measurement surface by means of the sliding that it has.
  • Retainer: It allows to support the thumb to move the cursor.
  • Locking screw: Screw located in the movable jaw, when being screwed allows to fix the obtained measurement acting on the blade of adjustment.
  • Vernier scale: Gauge scale that gives the precision of the tool according to its number of divisions.
  • Depth probe/rod: It is attached to the cursor and allows you to take measurements of depth.
Retainer Inside jaw Vernier scale Lockingscrew Insidemobile jaw Outside jawOutside mobile jaw Depth probe/rod


To know how to use the vernier and obtain a correct reading, two ways of using the instrument corresponding to the metric and English system are presented.

In the following example we can visually identify the measure:

Note: To better visualize you can zoom in on the search engine screen, the quality is not affected.

Vernier in millimeters

In the following image you can see the displaced moving jaw 2.4 cm (the 0 of the vernier is considered as reference), now we proceed to use the vernier to obtain the hundredths.

To know the hundredths, we will see which line corresponds to the vernier with the main rule. As a result, we obtain that the moving jaw was obtained displaced to 2.47 cm and this is how the result of the measurement is obtained.

Vernier in inches

For this case we have divided the main rule into 16 sections that complete an inch, taking as reference the number 0 of the vernier we can see that next figure corresponds to 0.9 in, but for the case of inches we will consider it as 15/16. Measurements with decimal number are considered in fraction, for example, if the moving jaw moves 3 inches plus a section between 3 and 4 inches, you should consider 3 in + (x) / 16, where x represents a number between 1 to 15 depending on the visions of the vernier.

15 / 16
= 0.9375

Now we proceed to use the vernier, for this case instead of considering 16 divisions, should be taken into account 128 divisions. Therefore we can observe that the line that coincides is approximately 5, then we should consider the value as 5/128 in.

5 / 128
= 0.0390625

Finally, we make the sum of the measures taken; 15/16 + 5/128 = 0.09375 + 0.0390625 = 0.9765625 in, converting it to centimeters 2.48cm.


We can different types of vernier calibers, such as:

  • M type vernier caliper with fine adjustment: Also known as vernier of depth bars, it is used to measure small interior dimensions, we can find ranges of 130, 180 and 280 mm, all with a resolution of 0.02mm.
  • CM type vernier caliper: This vernier has an open cursor and has a design in such a way that the external measuring tips are possible to be used in indoor measurement.
  • Caliper with dial indicator.
  • Digital vernier caliper: The advance of the technology allows to facilitate the task in the use of measuring instruments, that is why digital electronics is very applied for measuring tools. These calibrators employ a capacitance type displacement detection system, allows easy reading through a liquid crystal screen better known as LCD. Usually have a resolution of 0.01 mm but may vary according to the specifications of the company that makes it.
  • Vernier calipers with fine adjustment: Specially designed to measure external surfaces, or to allow only internal measurements with a range of 600 to 2000 mm and has a fine adjustment set screw.
  • Vernier caliper with adjustable probe with unequal tips: This type of vernier calibrator allows the measuring tip to be vertically adjusted on the head of the main boom, thus facilitating measurements in planes at different levels in staggered pieces.
  • Kafer caliper: Specially designed for the measurement of thickness in objects such as plastics, paper, cardboard, wires, threads and ropes. They can be found as analog or digital.
  • Double vernier caliper: Large size and precision, used for the measurement of gears.


Because it is a tool that is used in hostile environmental conditions and having a simple manufacturing structure tends to neglect the proper maintenance. For this reason, to obtain a better performance of these measuring instruments it is necessary to have standardized rules for a control of their maintenance.

For the storage of the vernier it is recommended that it is not exposed to dust, high humidity or extreme temperature fluctuations. It is advisable to apply antioxidant liquids to the cursor and to measuring faces if the tool is not going to be used for some time, it is also recommended to check once a month to verify if it is in good condition.

If working with chemical substances it is advisable to avoid the entry of vapors such as sulfuric acid of hydrochloric acid to the place where it is stored. The calibrators should be positioned so that the main boom does not flex and prevent the vernier from being damaged.