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Fractional inch to mm converter

Convert fractions like 3/8" or 1 1/4" to mm and decimal inches.

e.g. 3/8, 1 1/4, 0.625

Calculating…

How it's calculated

mm = inches × 25.4

Common sizes: 1/8" = 3.175 mm, 1/4" = 6.35 mm, 3/8" = 9.525 mm, 1/2" = 12.7 mm, 3/4" = 19.05 mm. Handy for imperial fasteners, BSP fittings, sockets and drills.