Match a measurement

The gap this site exists to close: on one side an exact measurement, on the other the fractions a rule actually has marks for. These four tools cross it, deterministically, with the error always stated.

Metric → fractional inches 6.7 mm → 17/64″ (+0.047 mm), with the candidates around it. Nearest fraction The closest mark on each rule: 16ths, 32nds, 64ths, 128ths. Simplest fraction within tolerance 10 mm ± 0.5 mm → 3/8″. The simplest fraction that truly fits. Fractions in a range Every standard fraction between two limits — stock, spacers, tolerances.

Where this comes from. Exact rational arithmetic on the values shown — fractions are pairs of integers until display, and inch–metric conversion uses 25.4 mm to the inch, exact by definition since 1959. See the full methodology.