Bolt Length Chart — Standard Length Range by Size, M3 to M36
Every bolt standard lists a shortest and a longest standard length for each size, and the ranges differ by type: an M10 hex screw threaded to the head (ISO 4017) runs from 20 to 100 mm, an M10 hex bolt with a plain shank (ISO 4014) from 45 to 100 mm, and an M10 socket head cap screw (ISO 4762) from 16 to 100 mm. EKINSUN LTD is a custom parts manufacturer that turns bolts and cap screws from bar in lengths from 6 to 400 mm, fully or partly threaded, from 1 piece.
| Size | Hex screw, full thread (ISO 4017) | Hex bolt, plain shank (ISO 4014) | Socket head cap screw (ISO 4762) | Cap screw threaded to the head up to |
|---|---|---|---|---|
| M3 | 6–30 | 20–30 | 5–30 | 20 |
| M4 | 8–40 | 25–40 | 6–40 | 25 |
| M5 | 10–50 | 25–50 | 8–50 | 25 |
| M6 | 12–60 | 30–60 | 10–60 | 30 |
| M8 | 16–80 | 40–80 | 12–80 | 35 |
| M10 | 20–100 | 45–100 | 16–100 | 40 |
| M12 | 25–120 | 50–120 | 20–120 | 50 |
| M14 | 30–1401 | 55–1403 | 25–140 | 55 |
| M16 | 30–1602 | 65–160 | 25–160 | 60 |
| M20 | 40–200 | 80–200 | 30–200 | 70 |
| M24 | 50–200 | 90–240 | 40–200 | 80 |
| M30 | 60–200 | 110–300 | 45–200 | 100 |
| M36 | 70–200 | 140–3604 | 55–200 | 110 |
¹ M14 in ISO 4017: the upper limit is from the 2022 edition; older tables do not list M14. ² M16 in ISO 4017: 160 mm in the 2022 edition (above 150 mm as product grade B); the 1999 edition ran to 200 mm, and many catalogues still do. ³ M14 in ISO 4014: 55 mm in the 2022 edition, 60 mm in the 2011 edition. ⁴ M36 in ISO 4014: range per the 2011 edition. The ranges are the standards' ranges, not what a given shop keeps on the shelf. ISO 4017 and ISO 4014 replaced DIN 933 and DIN 931; ISO 4762 replaced DIN 912.
Buying bolts in these lengths? Standard lengths in 8.8 steel and A2 stainless can also be supplied from stock; lengths between two steps, longer than the range, threaded to the head where the standard has a shank, or in A4 stainless, titanium or brass are made to order from 1 piece. The more pieces you order, the lower the unit price. Send the size, the length, the head type, the material and the quantity; quote in 12 hours.
Standard Length Steps — ISO 888
Bolt lengths come from one series (ISO 888): irregular steps up to 20 mm, 5 mm steps to 70 mm, 10 mm steps to 160 mm and 20 mm steps up to 500 mm. The product standards use the lengths of this list; a length such as 14, 22 or 75 mm is in the series but marked to be avoided.
| Length range | Standard lengths | Step |
|---|---|---|
| 2 to 20 mm | 2, 3, 4, 5, 6, 8, 10, 12, 16, 20 | irregular |
| 20 to 70 mm | 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70 | 5 mm |
| 70 to 160 mm | 70, 80, 90, 100, 110, 120, 130, 140, 150, 160 | 10 mm |
| 160 to 500 mm | 160, 180, 200, 220 … 480, 500 | 20 mm |
| In the list but to be avoided | 2.5, 7, 9, 11, 14, 18, 22, 28, 32, 38, 75, 85, 95, 105, 115, 125, 170, 190 | — |
How Bolt Length Is Measured
The nominal length l of a bolt or cap screw is measured from the bearing face under the head to the end of the thread; only screws whose head sits in a countersink are measured overall.
| Head type | Length l is measured | Example |
|---|---|---|
| Hex bolt and hex screw (ISO 4014, ISO 4017) | from under the head to the end | M8 × 40: 40 mm below the head |
| Socket head cap screw (ISO 4762), button head (ISO 7380) | from under the head to the end | M6 × 20: 20 mm below the head |
| Countersunk / flat head (ISO 10642, ISO 2009) | overall, head included | M5 × 16: 16 mm including the head |
| Set screw (ISO 4026 to ISO 4029), threaded rod | end to end | M8 × 10 set screw: 10 mm overall |
Thread Length on a Long Bolt
A partly threaded hex bolt (ISO 4014) has a thread length b set by the standard: b = 2d + 6 mm up to 125 mm long, 2d + 12 mm up to 200 mm and 2d + 25 mm above. A socket head cap screw is threaded to the head up to the length in the last column of the chart and has b = 2d + 12 mm above it. How the plain shank sets the grip, and how to order a different one, is on partially threaded bolts.
| Size | b for l ≤ 125 | b for 125 < l ≤ 200 | b for l > 200 |
|---|---|---|---|
| M3 | 12 | — | — |
| M4 | 14 | — | — |
| M5 | 16 | — | — |
| M6 | 18 | — | — |
| M8 | 22 | — | — |
| M10 | 26 | — | — |
| M12 | 30 | — | — |
| M14 | 34 | 40 | — |
| M16 | 38 | 44 | — |
| M20 | 46 | 52 | — |
| M24 | 54 | 60 | 73 |
| M30 | 66 | 72 | 85 |
| M36 | — | 84 | 97 |
Why Two Catalogues Give Different Longest Lengths
Most differences between catalogues come from the edition of the standard they were printed from. ISO 4017 ran M16 to 200 mm in its 1999 edition and to 160 mm in the 2022 edition; ISO 4014 moved the shortest M14 bolt from 60 mm (2011) to 55 mm (2022). ISO 4762 lists masses in its Annex A for M24 up to 240 mm and for M30 and M36 up to 300 mm, beyond the range of its main table, and catalogues copied from that annex show those lengths. A shop may also stock only part of a range, so the chart tells you what the standard allows, and the shop tells you what it has.
Longer Than the Longest Standard Length — What to Do
Past the end of a range there are two routes: a threaded rod with nuts, or a bolt made to the length. We make the second, from 1 piece. The same applies to lengths between two steps, full threads where the standard has a plain shank, and long bolts in stainless, titanium or brass.
| What you need | On the shelf? | What we do |
|---|---|---|
| A standard length inside the range in the chart, in 8.8 steel or A2 stainless (304, 1.4301) | Yes — hardware and industrial supply stores | Buy it from stock — from us (standard lengths can be supplied from stock; the more pieces, the lower the unit price) or, for one piece today, at a local hardware or industrial supply store. |
| A length between two standard lengths: M8 × 37, M10 × 58 | No | Cut from the next length and chamfered again, or made to the exact length from 1 piece. |
| Longer than the longest standard length: an M8 socket head cap screw 120 mm long, an M10 hex screw fully threaded to 150 mm | No | Made to order from 1 piece, fully or partly threaded; a threaded rod with nuts is the other route. |
| Threaded to the head in a length where the standard has a plain shank: M10 × 60 socket head cap screw | Partly | Made fully threaded to the length you need. |
| More thread than the standard b on a partly threaded bolt, or a set grip length | No | Made with the thread and grip on your drawing; see partially threaded bolts. |
| A long bolt in A4 stainless (316L, 1.4404), titanium or brass | Partly | Made to order in 316L, titanium grade 5 or brass CW614N. |
| An inch bolt (UNC or UNF) in a length the shelf skips | Partly | Made in the thread and length you name. |
Price for a long or special-length bolt: tap its row above, or send the size and the length. Made from 1 piece; the more pieces, the lower the unit price.
The pitch of every size is on the metric thread pitch chart, the tightening torque on the metric bolt torque chart and the hole for each size on the clearance hole chart.
Standard Bolt Lengths by Size — Quick Answers
What lengths do M4 bolts come in?
An M4 hex screw, fully threaded (ISO 4017), is standard from 8 to 40 mm; an M4 hex bolt with a plain shank (ISO 4014) from 25 to 40 mm; an M4 socket head cap screw (ISO 4762) from 6 to 40 mm, threaded to the head up to 25 mm. Longer M4 bolts are made to order.
What lengths do M5 bolts come in?
An M5 hex screw, fully threaded (ISO 4017), is standard from 10 to 50 mm; an M5 hex bolt with a plain shank (ISO 4014) from 25 to 50 mm; an M5 socket head cap screw (ISO 4762) from 8 to 50 mm, threaded to the head up to 25 mm. Longer M5 bolts are made to order.
What lengths do M6 bolts come in?
An M6 hex screw, fully threaded (ISO 4017), is standard from 12 to 60 mm; an M6 hex bolt with a plain shank (ISO 4014) from 30 to 60 mm; an M6 socket head cap screw (ISO 4762) from 10 to 60 mm, threaded to the head up to 30 mm. Longer M6 bolts are made to order.
What lengths do M8 bolts come in?
An M8 hex screw, fully threaded (ISO 4017), is standard from 16 to 80 mm; an M8 hex bolt with a plain shank (ISO 4014) from 40 to 80 mm; an M8 socket head cap screw (ISO 4762) from 12 to 80 mm, threaded to the head up to 35 mm. Longer M8 bolts are made to order.
What lengths do M10 bolts come in?
An M10 hex screw, fully threaded (ISO 4017), is standard from 20 to 100 mm; an M10 hex bolt with a plain shank (ISO 4014) from 45 to 100 mm; an M10 socket head cap screw (ISO 4762) from 16 to 100 mm, threaded to the head up to 40 mm. Longer M10 bolts are made to order.
What lengths do M12 bolts come in?
An M12 hex screw, fully threaded (ISO 4017), is standard from 25 to 120 mm; an M12 hex bolt with a plain shank (ISO 4014) from 50 to 120 mm; an M12 socket head cap screw (ISO 4762) from 20 to 120 mm, threaded to the head up to 50 mm. Longer M12 bolts are made to order.
What lengths do M16 bolts come in?
An M16 hex screw, fully threaded (ISO 4017), is standard from 30 to 160 mm (200 mm in the 1999 edition); an M16 hex bolt with a plain shank (ISO 4014) from 65 to 160 mm; an M16 socket head cap screw (ISO 4762) from 25 to 160 mm, threaded to the head up to 60 mm. Longer M16 bolts are made to order.
What lengths do M20 bolts come in?
An M20 hex screw, fully threaded (ISO 4017), is standard from 40 to 200 mm; an M20 hex bolt with a plain shank (ISO 4014) from 80 to 200 mm; an M20 socket head cap screw (ISO 4762) from 30 to 200 mm, threaded to the head up to 70 mm. Longer M20 bolts are made to order.
What lengths do M24 bolts come in?
An M24 hex screw, fully threaded (ISO 4017), is standard from 50 to 200 mm; an M24 hex bolt with a plain shank (ISO 4014) from 90 to 240 mm; an M24 socket head cap screw (ISO 4762) from 40 to 200 mm, threaded to the head up to 80 mm. Longer M24 bolts are made to order.
What lengths do M30 bolts come in?
An M30 hex screw, fully threaded (ISO 4017), is standard from 60 to 200 mm; an M30 hex bolt with a plain shank (ISO 4014) from 110 to 300 mm; an M30 socket head cap screw (ISO 4762) from 45 to 200 mm, threaded to the head up to 100 mm. Longer M30 bolts are made to order.
What to Send for a Quote
The thread (size and pitch, or inch size and threads per inch), the length under the head (or overall for a countersunk screw), the thread length or grip if it matters, the head type, the property class or material, and the quantity. For a replacement, a photo of the bolt beside a rule is enough. Any length from 6 to 400 mm, from 1 piece; quote in 12 hours.
On a custom shoulder bolt the length that matters is the ground shoulder under the head, not the overall length; the thread below it is short and set by the shoulder diameter, so quote the shoulder length and diameter rather than a length from this chart.
Bolt Length FAQ
Metric bolts come in the ISO 888 lengths: 2, 3, 4, 5, 6, 8, 10, 12, 16 and 20 mm, then 5 mm steps to 70 mm, 10 mm steps to 160 mm and 20 mm steps above that, up to 500 mm. Lengths such as 14, 22, 75 or 125 mm are in the list but marked to be avoided. Each bolt standard uses the part of the series that suits the diameter.
80 mm for all three common types: an M8 hex screw, fully threaded (ISO 4017), runs from 16 to 80 mm, an M8 hex bolt with a plain shank (ISO 4014) from 40 to 80 mm, and an M8 socket head cap screw (ISO 4762) from 12 to 80 mm. A longer M8 bolt is a threaded rod with nuts or a part made to order.
From under the head to the end of the bolt for hex bolts, hex screws, socket head cap screws and button head screws; over the full length, head included, for countersunk (flat head) screws; and end to end for set screws and threaded rod.
Take the next longer standard length and cut it, then chamfer the end again; the cut face loses its coating, and on a partially threaded bolt the plain shank stays as long as it was, so check the grip. Or have the bolt made to the exact length, from 1 piece.
Because the standard fixes its thread length: ISO 4014 gives b = 2d + 6 mm for lengths up to 125 mm, 2d + 12 mm up to 200 mm and 2d + 25 mm above, so an M10 × 100 hex bolt has 26 mm of thread. A socket head cap screw is threaded to the head up to a length that depends on its size (40 mm for M10) and partly threaded above it. A fully threaded bolt in a longer length is an ISO 4017 screw within ten times the diameter (200 mm at most), or a part made to order.
EKINSUN — a custom parts manufacturer that turns bolts and cap screws from bar in lengths from 6 to 400 mm, fully or partly threaded, in 8.8, 10.9 and 12.9 steel, A2 or A4 stainless, brass or titanium, from 1 piece. Send the thread, length, head type and material; quote in 12 hours.