Unit converter

The same conversion table the site's unit toggle reads, exposed directly. Every factor below is exact by definition rather than measured or rounded.

Quantity

1 mm = 0.039370 in

SI · mm This is what the database stores. Imperial is always computed. Imperial · in Shown to four decimal places; the factor itself is exact.

What this assumes

The inch is exactly 25.4 mm and the pound exactly 0.45359237 kg, by the international yard and pound agreement of 1959. The grain is exactly one seven-thousandth of a pound.
The pound-force follows from standard gravity, defined exactly as 9.80665 m/s², so the foot-pound-force and the psi are exact too.
One milliradian is a thousandth of a radian and one minute of angle is a sixtieth of a degree. The "1 MOA is about an inch at 100 yards" shorthand appears nowhere on this site: it is off by roughly 4.7%, which is a whole minute at 1000 yards.
SI is what ARMAG stores. Imperial is always computed on demand, never stored and never indexed — which is why this page converts rather than looks anything up.