What is a goniometer?

A goniometer also known as a universal protractor is an instrument that is used to measure angles.

Parts of a goniometer

This instrument is mainly composed of a semi-circle that graduated with 180º or a circle with 360º. There is a great variety of goniometers, some only have the graduated circle, others have a graduated ruler to measure distances, they can also have a rotary dial in which a vernier is inserted to take measurements with greater precision.


Main parts

  • Graduated Disc
  • Amplified lens
  • Squad
  • Squad expansion
  • Interchangeable strips
  • Fixing screws
  • Fine adjustment screw


Types of goniometers

There are different types since they have a variety of applications in industry and science.


It is the best-known type since it is the most common of its type.


With vernier scale

This type is characterized by having 1 smaller-scale integrated into the rotating disk, this goniometer is used to make measurements with greater precision.


Universal bracket

It is characterized by being a graduated ruler with an extra set of heads (angle head, centering head and a conveyor). When the ruler is used together with the protractor it acts as a goniometer.



This goniometer, being digital, does not omit parts, it has the same characteristics fixing screws, strip, bracket. The only element that changes is the scale graduated by a small screen that indicates the measurement.


Multifunctional digital

This instrument is characterized by having different functions included. Like those of a level and a goniometer.



It is used when precision tightening of screws is required. Some manufacturers, such as automotive or machinery manufacturers, specify the tightening of screws at angles.


With torque meter

It is used to make an angular tightening to adjust the engine head bolts.


For fingers

This goniometer is used for the branch of medicine but I put them on for you to know. It measures the range of motion of small joints.

goniometry for fingers

Goniometer reading

The reading is practically the same for all measuring instruments that use a vernier scale, zero indicates the value of the main scale and a line must be found that coincides with the main scale for the second value. In this case, we have to know that the main scale is in degrees and the vernier scale is in minutes.

Image measurement 50 degrees 20 minutes.


Why are the minutes used?

Regarding angular measurements, we always hear that they say 40 degrees and 25 minutes. Which can lead us to confusion, about what the minutes indicate in that measure?

It is only a matter of technique, a degree is divided into 60 equal parts which we call minutes, instead of saying this angle measures 0.45 degrees this angle is said to measure 0 degrees 45 minutes.

Don’t forget that being divided into 60 parts, 60 minutes equals 1 degree.