A caliper’s displayed increment is not the same as its accuracy. A digital model may show hundredths of a millimetre while its specified accuracy limit is several hundredths; a vernier model uses a graduation scale and has its own accuracy specification. This reference lists selected Mitutoyo models so the model number, range, accuracy and readout increment stay together. It covers these catalog entries only and does not define the tolerance of the part being measured.

Digital and vernier caliper tolerance reference

Separate accuracy from readout

For the listed digital models, the resolution is 0.01 mm. The catalog gives accuracy limits of ±0.03 mm for the 200 mm and 300 mm models, ±0.05 mm for the 450 mm and 600 mm models, and ±0.07 mm for the 1000 mm model. For the selected vernier models, graduations are 0.02 mm up to 1000 mm and 0.05 mm for the 1500 mm and 2000 mm models; their accuracy limits range from ±0.10 mm to ±0.28 mm.

A smaller display increment does not make a measurement accurate to that increment. Resolution describes the readout step; accuracy is a stated instrument performance limit. Calibration uncertainty, repeatability, operator technique, temperature and workpiece geometry add further considerations. A measurement decision should use the uncertainty and decision rules required by the quality system, not just the number of digits displayed.

Check range and measurement type

The catalog prints the minimum inside-diameter measurement in parentheses for the listed range. For example, a 0–200 mm digital model has a 10 mm minimum ID measurement, while several larger models list 20 mm. That parenthetical value matters when measuring a bore: the jaws may not reach the full zero point in the same way they do for outside measurements.

Choose a range that contains the feature and a caliper design intended for the measurement. Outside jaws, inside jaws, a depth bar and step faces do not necessarily produce identical error behavior. If a hole is smaller than the stated minimum ID range, a different instrument may be required. Do not extrapolate a manufacturer accuracy value to an unlisted size or special-purpose jaw geometry.

Compare the exact model

Model numbers distinguish digital and vernier versions as well as length. For example, the 160-131 is a 600 mm metric/metric dual-scale vernier caliper with a listed accuracy of ±0.10 mm and 0.02 mm graduation. The digital specifications use other order numbers and a 0.01 mm display resolution. Record the full number from the tool before using catalog data in an inspection plan.

For a nominal 100 mm dimension, the instrument’s overall range is not the only concern. Confirm that the tool is calibrated and appropriate for the required tolerance, and that the measurement method controls alignment, contact force and jaw condition. If a tolerance is close to the instrument’s accuracy limit, follow the applicable uncertainty and acceptance procedure rather than reporting extra decimal places as certainty.

Limits and calibration

These figures come from Mitutoyo’s caliper catalog section and apply to the specific models listed. The catalog does not turn them into calibration results for an individual instrument. Check the tool’s current calibration status, wear, zero setting, cleanliness and environmental conditions. A product catalog accuracy specification is not a certificate of traceability and is not automatically the uncertainty of a particular measurement.

Do not confuse instrument accuracy with a part tolerance. The engineering drawing or governing standard sets the allowable part size; the caliper specification describes the measuring tool. If the required decision is beyond the listed caliper capability, use a more suitable instrument and a measurement plan approved for the tolerance and feature geometry.

Source and scope

Data source: Mitutoyo caliper catalog, D section. Specifications are limited to the model numbers shown in the table.