BenchReference

Wrench & Socket Size Charts

Hex-head dimensions for standard bolts and nuts, and which wrench or socket fits them. Basic (nominal) dimensions per the cited standards; click a size for its full thread reference.

Head — top view Bolt — side view Nut — side view width across flats = wrench / socket size head height thickness
The wrench size is the width across flats (WAF) — measured flat-to-flat, not corner-to-corner.

Inch hex cap screws & finished hex nuts

Size Bolt wrench (WAF) Nut wrench (WAF) Head height Nut thickness Threads
1/4″ 7/16″ 7/16″ 5/32″ 7/32″ 1/4-20 · 1/4-28
5/16″ 1/2″ 1/2″ 13/64″ 17/64″ 5/16-18 · 5/16-24
3/8″ 9/16″ 9/16″ 15/64″ 21/64″ 3/8-16 · 3/8-24
7/16″ 5/8″ 11/16″ ≠ bolt 9/32″ 3/8″ 7/16-14 · 7/16-20
1/2″ 3/4″ 3/4″ 5/16″ 7/16″ 1/2-13 · 1/2-20
9/16″ 13/16″ 7/8″ ≠ bolt 23/64″ 31/64″ 9/16-12 · 9/16-18
5/8″ 15/16″ 15/16″ 25/64″ 35/64″ 5/8-11 · 5/8-18
3/4″ 1-1/8″ 1-1/8″ 15/32″ 41/64″ 3/4-10 · 3/4-16
7/8″ 1-5/16″ 1-5/16″ 35/64″ 3/4″ 7/8-9 · 7/8-14
1″ 1-1/2″ 1-1/2″ 39/64″ 55/64″ 1-8 · 1-12

Note the finished hex nut takes a larger wrench than the bolt head at 7/16″ (11/16 vs 5/8) and 9/16″ (7/8 vs 13/16) — that is per the standards, not an error.

Metric hex bolts & nuts (ISO)

Size Wrench (WAF) Legacy DIN wrench Head height (k) Nut height (m) Threads
M3 5.5 mm — 2 mm 2.4 mm M3 × 0.5
M3.5 6 mm — 2.4 mm 2.8 mm M3.5 × 0.6
M4 7 mm — 2.8 mm 3.2 mm M4 × 0.7
M5 8 mm — 3.5 mm 4.7 mm M5 × 0.8
M6 10 mm — 4 mm 5.2 mm M6 × 1
M8 13 mm — 5.3 mm 6.8 mm M8 × 1.25 · M8 × 1
M10 16 mm 17 mm 6.4 mm 8.4 mm M10 × 1.5 · M10 × 1 · M10 × 1.25
M12 18 mm 19 mm 7.5 mm 10.8 mm M12 × 1.75 · M12 × 1.25 · M12 × 1.5
M14 21 mm 22 mm 8.8 mm 12.8 mm M14 × 2 · M14 × 1.5
M16 24 mm — 10 mm 14.8 mm M16 × 2 · M16 × 1.5
M18 27 mm — 11.5 mm 15.8 mm M18 × 2.5 · M18 × 1.5
M20 30 mm — 12.5 mm 18 mm M20 × 2.5 · M20 × 1.5
M22 34 mm 32 mm 14 mm 19.4 mm M22 × 2.5
M24 36 mm — 15 mm 21.5 mm M24 × 3

ISO and legacy DIN wrench sizes differ at M10, M12, M14, and M22 — older equipment often uses the DIN size. Bolts and nuts share the same WAF in the metric series.

Metric ↔ SAE socket comparison

The nearest SAE socket for every metric size, with the exact difference. Sockets within ≈0.15 mm are generally interchangeable in practice; larger gaps risk rounding the fastener. The bar shows each difference against that band: dot left of center = SAE is smaller (binds or won't seat), right = larger (loose); inside the shaded band = close.

Metric socket Nearest SAE SAE in mm Difference Fit
4 mm 5/32″ 3.969 −0.031 mm close — usually interchangeable
4.5 mm 3/16″ 4.762 +0.262 mm loose/tight — use with care
5 mm 3/16″ 4.762 −0.238 mm loose/tight — use with care
5.5 mm 7/32″ 5.556 +0.056 mm close — usually interchangeable
6 mm 1/4″ 6.35 +0.350 mm loose/tight — use with care
7 mm 9/32″ 7.144 +0.144 mm close — usually interchangeable
8 mm 5/16″ 7.938 −0.063 mm close — usually interchangeable
9 mm 11/32″ 8.731 −0.269 mm loose/tight — use with care
10 mm 13/32″ 10.319 +0.319 mm loose/tight — use with care
11 mm 7/16″ 11.112 +0.112 mm close — usually interchangeable
12 mm 15/32″ 11.906 −0.094 mm close — usually interchangeable
13 mm 1/2″ 12.7 −0.300 mm loose/tight — use with care
14 mm 9/16″ 14.287 +0.287 mm loose/tight — use with care
15 mm 19/32″ 15.081 +0.081 mm close — usually interchangeable
16 mm 5/8″ 15.875 −0.125 mm close — usually interchangeable
17 mm 21/32″ 16.669 −0.331 mm loose/tight — use with care
18 mm 11/16″ 17.462 −0.538 mm loose/tight — use with care
19 mm 3/4″ 19.05 +0.050 mm close — usually interchangeable
20 mm 25/32″ 19.844 −0.156 mm loose/tight — use with care
21 mm 13/16″ 20.637 −0.363 mm loose/tight — use with care
22 mm 7/8″ 22.225 +0.225 mm loose/tight — use with care
23 mm 7/8″ 22.225 −0.775 mm loose/tight — use with care
24 mm 15/16″ 23.813 −0.188 mm loose/tight — use with care
25 mm 1″ 25.4 +0.400 mm loose/tight — use with care
26 mm 1″ 25.4 −0.600 mm loose/tight — use with care
27 mm 1-1/16″ 26.987 −0.013 mm close — usually interchangeable
28 mm 1-1/8″ 28.575 +0.575 mm loose/tight — use with care
29 mm 1-1/8″ 28.575 −0.425 mm loose/tight — use with care
30 mm 1-3/16″ 30.162 +0.162 mm loose/tight — use with care
32 mm 1-1/4″ 31.75 −0.250 mm loose/tight — use with care
33 mm 1-5/16″ 33.337 +0.337 mm loose/tight — use with care
34 mm 1-5/16″ 33.337 −0.663 mm loose/tight — use with care
35 mm 1-3/8″ 34.925 −0.075 mm close — usually interchangeable
36 mm 1-7/16″ 36.512 +0.512 mm loose/tight — use with care
Data provenance. ASME B18.2.1, Hex Cap Screws (head dimensions) (ASME). ASME B18.2.2, Finished Hex Nuts (ASME). ISO 4014 / ISO 4017, Hexagon head bolts and screws (ISO). ISO 4032, Hexagon regular nuts, style 1 (ISO). Socket comparison is computed from nominal wrench sizes (1 in = 25.4 mm exactly); actual fit also depends on socket tolerance and fastener condition. See all data sources.