12 mm to inches

Formula: inches = millimeters ÷ 25.4 (exact). Or multiply by 0.0393701 for a quick estimate of the same definition.

1. Start with 12 mm.
2. Divide by 25.4: 12 ÷ 25.4 = 0.4724 in.
3. Reverse check: 0.4724 × 25.4 = 12 — the conversion round-trips cleanly.

Dividing by 25.4 is exact: 12 ÷ 25.4 = 0.47244094 in, shown as 0.4724 in. 15/32 in is the nearest 1/64, not an equal. 1/2 in is a different size, 0.7 mm larger.

The decimal column is exact (shown to four places). The fraction is the nearest 1/64 approximation used on rulers and bit charts — so the two can disagree. Here, 12 mm = 0.4724 in exactly, while 15/32 in differs by -0.094 mm. The converter disclaimer (“rounded to the nearest 1/64 fraction”) exists so that difference is never mistaken for a data error.

No. 1/2 in equals 12.7 mm, so 12 mm is 0.7 mm smaller. The exact decimal is 0.4724 in. The nearest 1/64 is 15/32 in (11.90625 mm), which is 0.09375 mm smaller than 12 mm. Plywood, tube, and drill bits marked 12 mm are neither 15/32 in nor 1/2 in.

Compared with 1/2 in (12.70 mm): 12 mm is -0.700 mm (metric size is smaller).

This page is for specification checks — drill bits, sockets, tubing, and stock — not body measurements. For shop picks across many metric diameters, see the drill bit & socket mm to inches chart.

Metric plywood and birch ply are commonly stocked at 12 mm, which is 0.4724 in. That is 0.09375 mm thicker than 15/32 in (11.90625 mm) and 0.7 mm thinner than a true 1/2 in (12.7 mm). A dado or groove cut for one will be loose or tight for the other. 12 mm outside-diameter tube — furniture frames, metric brake line, small copper — is the same 0.4724 in OD, not 1/2 in pipe. A 12 mm drill bit cuts 0.4724 in; a 1/2 in bit cuts 12.7 mm and leaves a 0.7 mm larger hole.