The Vernier Caliper

The vernier caliper, also called a caliper, is a measuring instrument that provides greater precision than a millimeter ruler.

The caliper has several jaws and a depth probe that make it easy to measure external diameters, internal diameters, and depths.

The vernier scale is an auxiliary scale that allows distance measurements with a precision ranging from 0.1 millimeters to 0.02 millimeters. This precision is ten times greater, or more, than that of a millimeter ruler.

Parts of the Vernier Caliper

A vernier caliper is made up of the following parts:

Calibre de medida con sus partes señaladas por números.

Parts of a vernier caliper.

  1. External measuring jaws.
  2. Internal measuring jaws.
  3. Depth probe.
  4. Main millimeter scale.
  5. Vernier scale for reading fractions of a millimeter.
  6. Sliding thumbwheel.
  7. Locking screw.
  8. Slider (moving part of the caliper).
  9. Beam (fixed part of the caliper).
Corredera de un calibre moviéndose sobre la regla.

The slider of a caliper moving along the beam.

Measuring with a Vernier Caliper

The following images show how to measure the external dimensions, internal dimensions, and depth of a part.

Measuring external dimensions
  • Open the external measuring jaws (1) and place the object between them.
  • Slide the jaws closed until they touch the object without applying excessive force.
  • Read the main scale (the mark immediately before the zero on the vernier scale).
  • Read the vernier scale (the number whose line aligns with a line on the main scale).
  • Add both readings to obtain the final measurement.
Calibre tomando una medida exterior.

A caliper taking an external measurement.

Measuring internal dimensions
  • Close the internal measuring jaws (2) and place them inside the gap or hole to be measured.
  • Slide the jaws open until they touch the object without applying excessive force.
  • Read the main scale (the mark immediately before the zero on the vernier scale).
  • Read the vernier scale (the number whose line aligns with a line on the main scale).
  • Add both readings to obtain the final measurement.
Calibre tomando una medida interior.

A caliper taking an internal measurement.

Measuring Depth
  • Close the caliper and place its rear face against the opening to be measured, as shown in the figure below.
  • Slide the depth rod outward until it touches the bottom of the object without applying excessive force.
  • Read the main scale (the mark immediately before the zero on the vernier scale).
  • Read the vernier scale (the number whose line aligns with a line on the main scale).
  • Add both readings to obtain the final measurement.
Calibre tomando una medida de profundidad.

A caliper taking a depth measurement.

Reading the Vernier Scale

The whole-millimeter measurement can be read on the main scale at the position of the zero mark on the vernier scale.

The tenths-of-a-millimeter measurement can be read at the point where one of the lines on the vernier scale aligns exactly with a line on the main scale.

Medición de una distancia de 16,6 milímetros con un calibre.

Measurement of a distance of 16.6 millimeters.

The zero mark is past 16 millimeters but has not yet reached 17 millimeters on the upper scale.

The 6 mark on the vernier scale aligns with a mark on the upper scale.

Medición de una distancia de 24,0 milímetros con un calibre.

Measurement of a distance of 24.0 millimeters.

The zero mark aligns with 24 millimeters on the upper scale.

The only mark on the vernier scale that aligns with a mark on the main scale is the zero mark.

Medición de una distancia de 9,9 milímetros con un calibre.

Measurement of a distance of 9.9 millimeters.

The zero mark is past 9 millimeters but has not yet reached 10 millimeters on the upper scale.

The 9 mark on the vernier scale aligns with a mark on the upper scale.

Virtual Vernier Caliper

Simulation of a caliper with a precision of 0.05 millimeters.

Measurement exercises

Worksheet with exercises for reading measurements using a vernier caliper.

Vernier Caliper Measurement Exercises. PDF format.