Wrench Size Chart & Calculator (Across Flats / SW)
Metric Thread & SW Reference
| Thread Size (Nominal Diameter) |
SW Width (Width Across Flats) |
Head Height (k) |
|---|---|---|
| M5 | 8 | 3.5 |
| M6 | 10 | 4 |
| M8 | 13 | 5.3 |
| M10 | 17 | 6.4 |
| M12 | 19 | 7.5 |
| M14* | 22 | 8.8 |
| M16 | 24 | 10 |
| M18* | 27 | 11.5 |
| M20 | 30 | 12.5 |
| M22* | 32 | 14 |
| M24 | 36 | 15 |
| M27* | 41 | 17 |
| M30 | 46 | 18.7 |
| M33* | 50 | 21 |
| M36 | 55 | 22.5 |
| M39* | 60 | 24 |
| M42 | 65 | 26 |
| M45* | 70 | 28 |
| M48 | 75 | 30 |
| M52* | 80 | 33 |
| M56 | 85 | 35 |
| M60* | 90 | 38 |
| M64 | 95 | 40 |
* Second-choice (less preferred) metric sizes per ISO 3 preferred number series.
Data referenced from ISO 4017 (DIN 933) — Hexagon head screws — Product grades A and B.
Wrench Size Calculator
Find across flats dimensions (AF / SW:Schlüsselweite) for hex fasteners.
Shaft & Hexagon Fit Diagram:
Double-Headed Open-Ended Wrench:
Shaft Diameter Samples:
ISO 10102:2018 Assembly tools for screws and nuts - Double-headed open-ended engineers' wrenches.
ISO 3318:2016 Assembly tools for screws and nuts - Open-ended wrenches, box wrenches and combination wrenches - Maximum widths of heads.
ISO 1085:2016 Assembly tools for screws and nuts - Double-ended wrenches - Size pairing.
ISO 691:2005 Assembly Tools for Screws and Nuts - Wrench and Socket Openings - Tolerances for General Use
ISO 272:1979 Hexagon products — Widths across flats (the defining standard for SW/AF dimensions on bolts and nuts).
ISO 4014:2011 Hexagon head bolts — Product grades A and B (full thread length variant).
ISO 4032:2012 Hexagon nuts, style 1 — Product grades A and B.
DIN 3110:1987 Engineers wrenches, double head, open end, with unequal jaw widths; test torques series c.
DIN 475-2:1982 Wrench and socket openings.
Frequently Asked Questions
What does Wrench Size Chart & Calculator do?
Wrench size chart and calculator: find width across flats (SW/AF) for metric and imperial bolts and nuts.
How do I use Wrench Size Chart & Calculator?
Enter a bolt or shaft diameter in mm. The chart shows the standard width across flats (SW/AF) for metric hex fasteners, with ISO 272 reference values.
Is Wrench Size Chart & Calculator free to use?
Yes. The wrench size chart and SW calculator are free and browser-based with no installation needed.