Anchor and Chain Sizing Guide
Don't know your chain size yet?
This table works backwards from a chain diameter you already have. If you are starting from the vessel instead, our Anchor & Chain Sizing Calculator works out the Equipment Number from its displacement, breadth and profile area, then returns the anchor mass, chain length and diameter the IACS tables require — and the chain and Kenters that match.
Use this table to match anchor mass, chain diameter and chain length. The figures are taken from the IACS equipment number tables — the same standard your classification society applies — so a chain and anchor selected from one row will be consistent with each other.
How To Use This Table
Find your chain diameter in the first column. That row gives the bower anchor mass your vessel should carry, the chain breaking load, and the chain length normally specified.
Don't know your chain size? Measure one link. Link length is approximately 6 × the chain diameter and link width approximately 3.6 × the diameter — so an 80mm long link is 80 ÷ 6 = 13.3mm chain, or 1/2". Send us measurements and photographs and we will identify it.
Chain Size, Anchor Mass and Chain Length
| Chain dia. | Imperial | Kenter | Grade 1 breaking load | Grade 2 breaking load | Grade 3 breaking load | Stockless anchor | HHP anchor | Chain per anchor | Chain weight per shot |
|---|---|---|---|---|---|---|---|---|---|
| 20.5mm | 13/16" | 20.5mm Kenter | 175 kN / 18 t | 244 kN / 25 t | 349 kN / 36 t | 660 kg | 495 kg | 5.5 shots (495 ft) | 265 kg |
| 22mm | 7/8" | 22mm Kenter | 200 kN / 20 t | 280 kN / 29 t | 401 kN / 41 t | 780 kg | 585 kg | 6.0 shots (540 ft) | 300 kg |
| 24mm | 15/16" | 24mm Kenter | 237 kN / 24 t | 332 kN / 34 t | 476 kN / 49 t | 900–1,020 kg | 675–765 kg | 6.5 shots (585 ft) | 360 kg |
| 26mm | 1" | 26mm Kenter | 278 kN / 28 t | 389 kN / 40 t | 556 kN / 57 t | 1,140 kg | 855 kg | 7.0 shots (630 ft) | 420 kg |
| 28mm | 1-1/8" | 28mm Kenter | 321 kN / 33 t | 449 kN / 46 t | 642 kN / 65 t | 1,290 kg | 970 kg | 7.0 shots (630 ft) | 490 kg |
| 30mm | 1-3/16" | 30mm Kenter | 368 kN / 38 t | 514 kN / 52 t | 735 kN / 75 t | 1,440–1,590 kg | 1,080–1,193 kg | 7.5 shots (675 ft) | 565 kg |
| 32mm | 1-1/4" | 32mm Kenter | 417 kN / 43 t | 583 kN / 59 t | 833 kN / 85 t | 1,740 kg | 1,305 kg | 8.0 shots (720 ft) | 635 kg |
| 34mm | 1-3/8" | 34mm Kenter | 468 kN / 48 t | 655 kN / 67 t | 937 kN / 96 t | 1,920 kg | 1,440 kg | 8.0 shots (720 ft) | 720 kg |
| 36mm | 1-7/16" | 36mm Kenter | 523 kN / 53 t | 732 kN / 75 t | 1,050 kN / 107 t | 2,100–2,280 kg | 1,575–1,710 kg | 8.5 shots (765 ft) | 800 kg |
| 38mm | 1-1/2" | 38mm Kenter | 581 kN / 59 t | 812 kN / 83 t | 1,160 kN / 118 t | 2,460 kg | 1,845 kg | 8.5 shots (765 ft) | 895 kg |
| 40mm | 1-9/16" | 40mm Kenter | 640 kN / 65 t | 896 kN / 91 t | 1,280 kN / 131 t | 2,640 kg | 1,980 kg | 8.5 shots (765 ft) | 1,000 kg |
| 42mm | 1-5/8" | 42mm Kenter | 703 kN / 72 t | 981 kN / 100 t | 1,400 kN / 143 t | 2,850 kg | 2,140 kg | 9.0 shots (810 ft) | 1,100 kg |
| 44mm | 1-3/4" | 44mm Kenter | 769 kN / 78 t | 1,080 kN / 110 t | 1,540 kN / 157 t | 3,060 kg | 2,295 kg | 9.0 shots (810 ft) | 1,200 kg |
| 46mm | 1-13/16" | 46mm Kenter | 837 kN / 85 t | 1,170 kN / 119 t | 1,680 kN / 171 t | 3,300 kg | 2,475 kg | 9.0 shots (810 ft) | 1,300 kg |
| 48mm | 1-7/8" | 48mm Kenter | 908 kN / 93 t | 1,270 kN / 130 t | 1,810 kN / 185 t | 3,780 kg | 2,835 kg | 9.5 shots (855 ft) | 1,440 kg |
What Is the Equipment Number (EN)?
The table above and the one below both key off a vessel's Equipment Number — a single figure classification societies calculate from a ship's displacement, breadth, and the height and area of its hull and superstructure above the waterline:
EN = Δ2/3 + 2.0(hB + Sfun) + A/10
where Δ is moulded displacement (t), B is moulded breadth (m), h is the effective height from the waterline to the top of the uppermost house, Sfun is the funnel's effective projected area, and A is the side projected area of the hull and superstructure above the waterline. A bigger, taller, more heavily built vessel gets a bigger EN, which is why anchor mass and chain diameter scale directly off it rather than off length alone.
You don't need to calculate this yourself — tell us your vessel's equipment number (it's usually on the ship's certificate or stability book) or its principal dimensions and we'll work it out.
Smaller Vessels — Equipment Number Below 205
The table above (IACS UR A1) starts at EN 205 / 20.5mm chain. Smaller vessels — EN 50 to 205 — are covered by a separate document, IACS Recommendation No. 10 ("Anchoring, Mooring and Towing Equipment"), which is where our 16mm and 19mm sizes come from. One row per equipment-number band — the same chain diameter can serve two adjacent bands (the anchor gets heavier before the chain needs to get thicker), and Grade 1 needs a larger diameter than Grade 2 or 3 for the same band, shown separately.
| Equipment No. | Chain dia. (Gr. 2/3) | Imperial | Kenter | Grade 1 (larger dia.) | Grade 2 breaking load | Grade 3 breaking load | Stockless anchor | Chain length |
|---|---|---|---|---|---|---|---|---|
| EN 50–70 | 12.5mm | 1/2" | — | 14mm — 82 kN / 8.4 t | 92 kN / 9.4 t | 132 kN / 13.5 t | 180 kg | 220 m total |
| EN 70–90 | 14mm | 9/16" | — | 16mm — 107 kN / 10.9 t | 116 kN / 11.8 t | 165 kN / 16.8 t | 240 kg | 220 m total |
| EN 90–110 | 16mm | 5/8" | 16mm Kenter | 17.5mm — 127 kN / 13 t | 150 kN / 15.3 t | 216 kN / 22 t | 300 kg | 247.5 m total |
| EN 110–130 | 17.5mm | 11/16" | — | 19mm — 150 kN / 15.3 t | 179 kN / 18.3 t | 256 kN / 26.1 t | 360 kg | 247.5 m total |
| EN 130–150 | 17.5mm | 11/16" | — | 20.5mm — 175 kN / 17.8 t | 179 kN / 18.3 t | 256 kN / 26.1 t | 420 kg | 275 m total |
| EN 150–175 | 19mm | 3/4" | 19mm Kenter | 22mm — 200 kN / 20.4 t | 211 kN / 21.5 t | 301 kN / 30.7 t | 480 kg | 275 m total |
| EN 175–205 | 20.5mm | 13/16" | 20.5mm Kenter | 24mm — 237 kN / 24.2 t | 244 kN / 24.9 t | 349 kN / 35.6 t | 570 kg | 302.5 m total |
Figures from IACS Recommendation No. 10, Rev.4 2020, Table 1 and Table 2. Supplied for guidance — confirm requirements with your classification society or surveyor.
Notes On The Figures
- A shot is a standard length of anchor chain: 27.5 m (90 ft). Chain is supplied in shots and joined with Kenter shackles.
- Chain per anchor is half the total chain length specified, since a vessel carries two bower anchors.
- Stockless vs HHP. A high holding power anchor achieves the same holding at roughly 75% of the mass of a stockless anchor, so it is lighter to handle and cheaper to ship.
- All three grades are shown for reference. Grade 3 is our working standard for anchor and mooring chain and what we stock Kenters for. Joining shackles must always match the grade of the chain.
- Chain under 20.5mm is not normally supplied in Grade 3 — smaller sizes run Grade 1 or Grade 2.
What You Need For A Chain Replacement
A complete chain outfit for one anchor needs more than the chain itself:
- Chain — the number of shots from the table above
- Kenter joining shackles — one per shot
- Lead plugs — one per Kenter, mandatory, single use
- Drive pin punch — sized to the chain, for future disassembly
- End shackle — chain to anchor
We supply all of these, and Kenter shackles are held in stock in Montreal for immediate despatch.
Matching Anchors
We supply stockless and high holding power bower anchors to the masses shown above, certified to ABS or Lloyd's Register. Anchors are quoted to order — tell us your chain size or equipment number and we will quote the matching anchor.
Need Help Sizing?
Send us your chain measurements, your vessel's equipment number, or photographs of the existing chain and anchor, and we will tell you what you need. We answer technical questions whether or not you order from us.
Figures derived from IACS equipment number tables and IACS UR A1. Supplied for guidance — confirm requirements with your classification society or surveyor.
Dibblee Industries Ltd. / Les Industries Dibblee Ltée, Montreal, Quebec.