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Circular Vernier made for
Picatinny Arsenal

How to read a vernier To read a vernier scale to 1/50 mm or 0.020 mm, the vernier scale must have 49 mm divided into 50 equal spaces for use with 1.0 mm graduations on the true (or main) scale ( click here to see our example of verniers in a pop up window) or go to the example page and print it out for your reference.

First, look at the metric example.
The vernier “0″ is between 30.4 cm (304mm) and 30.5 cm (305mm).  To determine the precise location, count across the vernier from “0″ to see which line exactly coincides with a line on the true (or main) scale.  It is the 33rd line.   Therefore, the correct reading to 1/50mm is 304.00mm + 33 x .02mm = 304.66 mm (or 30.466 cm).

Likewise, for the inch vernier, to read to 0.001″, one must have 50 graduations on the vernier over 49 spaces of 1/20″ (or 0.05″) graduations on the true (or main) scale (1/50 x 1/20 = .001″).

Now, look at the inch example.   “0″ on the vernier is between 12.000″ and 12.050″ on the true scale.  Count from “0″ to the first line that coincides exactly with a line on the true (or main) scale which is the 8th.  Therefore, the correct reading is 12.000″ + 8 x 0.001″ = 12.008″.

Other combinations of main scale graduations and vernier graduations are possible for both inch and metric reading for these or other resolutions.  For example, for 1/10 mm (0.1mm) resolution, one needs only 10 graduations on the vernier over 9 (1mm) graduations on the main scale (1/10 x 1 = 0.1mm resolution, etc…

For angular verniers, the same principle applies.  For 1/10º (0.1º), one may have the main or true scale divided into 360 x 1° increments; and the vernier divided into 10 graduations over 9° of the main scale.   The reading is the same as for linear scales.

Likewise, angular verniers can be used to accurately read degrees, minutes or military units.

A caliper is used in many fields such as metalworking, woodworking, and mechanical engineering.  It must be properly applied against the part being measured in order to take the desired measurement.  For example, when measuring the thickness of a plate a vernier caliper must be held at right angles to the piece.  Some practice may be needed to measure round or irregular objects correctly.  Accuracy of measurement when using a caliper is highly dependent on the skill of the operator. Regardless of the type, a caliper’s jaws must be forced into contact with the part being measured. As both the part and caliper are always to some extent elastic, the amount of force used affects the indication. A consistent, firm touch is correct.  Too much force results in an underindication as part and tool distort; too little force gives insufficient contact and an overindication.  This is a greater problem with a caliper incorporating a wheel, which lends mechanical advantage. This is especially the case with digital calipers, calipers out of adjustment, or calipers with a poor quality beam.

Simple calipers are uncalibrated; the measurement taken must be compared against a scale. Whether the scale is part of the caliper or not, all analog calipers—verniers and dials—require good eyesight in order to achieve the highest precision. Digital calipers have the greatest advantage in this area.

Calibrated calipers may be mishandled, leading to loss of zero. When a caliper’s jaws are fully closed, it should of course indicate zero. If it does not, it must be recalibrated or repaired. It might seem that a vernier caliper cannot get out of calibration but a drop or knock can be enough. Digital calipers have zero set buttons.

Vernier, dial and digital calipers can be used with accessories that extend their usefulness. Examples are a base that extends their usefulness as a depth gauge and a jaw attachment that allows measuring the center distance between holes. Since the 1970s a clever modification of the moveable jaw on the back side of any caliper allows for step or depth measurements in addition to external caliper measurements, in similar fashion to a universal micrometer.