How to Test Calipers


You can find calipers in the toolboxes of machinists, wood workers and home remodeling enthusiasts around the world. A versatile tool, basic calipers offer three primary methods of measurement: inside jaws to measure holes or bores, outside jaws to measure external lengths, and a depth probe to measure steps and thicknesses the jaws cannot reach. While most basic calipers have an accuracy of +/- .001-inch, each measurement tool on the caliper can read slightly differently. Test the calipers against calibrated standards to ensure accurate measurements.

Things You'll Need

  • Clean cloth
  • Gauge blocks
  • Outside micrometer
  • Clean the caliper. Wipe the flat faces on the inside and outside jaws with a clean cloth to remove debris or residue.

  • Select a calibrated gauge block. Note the exact size of the block.

  • Set the block on a flat surface, then open the outside jaws of the micrometer wider than the length of the block. Close the outside jaws of the caliper so that the flat edges of the jaws are flush against the edges of the gauge block. Compare the caliper's reading against the known dimension of the gauge block.

  • Stand the gauge block upright on a flat surface, such as a granite block. Open the caliper wider than the dimension of the block. The caliper's depth probe will exit the right side of the caliper. Set the end of the depth probe against the block on the flat surface, then slowly lower the main body of the caliper until its flat right end lays flush against the top of the gauge block. Compare the measured value against the known value of the gauge block.

  • Close the anvil and spindle of an outside micrometer around the gauge block. Lock the micrometer spindle securely in place and wiggle the gauge block free from the micrometer. Measure the distance between the faces of the locked anvil and spindle with the inside jaws of the caliper. Ensure the flat edges of the jaws lie flush with the flat faces of the anvil and spindle. Compare the caliper's measurement with the known value of the gauge block.

  • Repeat with gauge blocks of differing sizes if any of the initial caliper measurements are questionable.

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  • Photo Credit caliper image by laviniaparscuta from
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