How to Use a Slide Caliper

The word caliper is an abbreviation of caliper compass.  Calipers are used for several measurements and consist of a precision beam with an integral scale.

They also have two sets of jaws, fixed and sliding.  Center measuring, gear tooth, machine travel, nib jaws, pocket or rolling mill, slide caliper, and spring or firm-joint or some of the popular types of calipers.

Slide calipers typically use a precise slide movement for inside, outside, depth, or step measurements.  There are three types of slide calipers: vernier, dial, and electronic.  Here are instructions for using a vernier caliper.

Things you will need

  • Vernier caliper
  • Object to measure


  1. Know how to read the scale on a caliper – On the bottom of the scale is a row of numbers with a zero mark. To determine millimeters count the number of full marks that occur above and to the left of the zero mark. To determine tenths of millimeters, peruse the bottom scale marks and identify a bottom mark that aligns perfectly with a top mark.  The number of tenths is the number written below the mark on the bottom scale.
  2. Check to ensure the scale works properly by loosening the locking screw and moving the slider.  Ensure the caliper has a zero reading when fully closed.
  3. Fit the caliper onto the object to be measured and close the jaws lightly.
  4. When measuring an object with a round cross-section, ensure its axis is perpendicular to the caliper to ensure you are measuring the full diameter.
  5. Ignore the top scale, which is calibrated in inches.   Use the bottom scale, which is in metric units.
  6. Note the fixed scale and sliding scale.   The boldface numbers on the fixed scale are centimeters.   The tick marks on the fixed scale between the boldface numbers are millimeters.
  7. There are ten tick marks on the sliding scale. The left-most tick mark on the sliding scale will let you read from the fixed scale the number of whole millimeters that the jaws are opened.
  8. Read the centimeter mark on the fixed scale to the left of the 0-mark on the vernier scale.  Find the millimeter mark on the fixed scale that is just to the left of the 0-mark on the vernier scale
  9. Identify the tenths of millimeters as outlined in step one and add the number to the previous reading.