Screw size converter

M1.2 (1.20 mm / 0.0472 in)

#0-80 UNF (1.52 mm) is the closest imperial screw, but it is bigger — not a substitute

M1.4 (1.40 mm / 0.0551 in)

#0-80 UNF (1.52 mm) — close in diameter, different pitch, do not mix

M1.6 (1.60 mm / 0.0630 in)

#1-72 UNF (1.85 mm) is larger; there is no true imperial equivalent

M2 (2.00 mm / 0.0787 in)

#2-56 UNC (2.18 mm) is close but not interchangeable

M2.5 (2.50 mm / 0.0984 in)

#3-48 / #4-40 (2.51 / 2.84 mm) — #4-40 is the common US stand-in and it will NOT thread in

M3 (3.00 mm / 0.1181 in)

#5-40 (3.18 mm) or #4-40 — neither interchanges with M3

M4 (4.00 mm / 0.1575 in)

#8-32 (4.17 mm) — the standard US PC/rack screw, close but not the same

M5 (5.00 mm / 0.1969 in)

#10-32 (4.83 mm) — the other common rack thread; check before mixing

M6 (6.00 mm / 0.2362 in)

1/4in-20 (6.35 mm) — the tripod/camera thread; visibly larger than M6