To match an anchor chain to your windlass, measure three link dimensions — D (wire diameter), P (inside link pitch) and W (inside link width) — and match all three to a chain standard such as DIN 766, ISO 4565 or ACCO G4; diameter alone is not enough. This guide explains how to take those measurements and includes MAURIPRO's full D, P & W chart so you can identify your chain and find the exact replacement.
Anchor chain standards at a glance
| Standard | Sizing | Typical range | Notes |
|---|---|---|---|
| DIN 766 | Metric (mm) | 6–16 mm | Calibrated short-link chain; the most common fit for European metric windlass gypsies. |
| ISO 4565 | Metric (mm) | 6–10 mm | Metric calibrated chain with slightly different pitch/width than DIN 766 of the same nominal size. |
| ACCO ISO G43 (G4) | Imperial (in) | 1/4"–1/2" | High-test grade with longer link pitch; standard on many US-market windlasses. |
| ACCO BBB (3B) | Imperial (in) | 1/4" and up | Short-pitch imperial chain found on many older US windlass gypsies. |
What do D, P and W mean on an anchor chain?
Chain is matched to a windlass by its calibrated link geometry, not just its nominal size. Measure three things on your existing chain:
- D — link diameter: the thickness of the wire the link is made from.
- P — link pitch: the inside length of a single link.
- W — link width: the inside width of a single link.
Two chains with the same nominal size (say 8 mm) can have different P and W depending on the standard (DIN, ISO, ACCO, G4). Those small differences are what determine whether the chain seats correctly in your windlass gypsy — so always match all three dimensions, not just the diameter.
Which chain matches my measurements? The full D, P & W chart
Measure D, P and W on a single link of your chain (in mm or inches) and match the numbers to the chain model below:
| Chain model | D (mm) | D (in) | P (mm) | P (in) | W (mm) | W (in) |
|---|---|---|---|---|---|---|
| 6 mm DIN 766 | 6.00 | 0.24 | 18.50 | 0.73 | 20.40 | 0.80 |
| 6 mm ISO 4565 | 6.00 | 0.24 | 18.00 | 0.71 | 21.60 | 0.85 |
| 1/4" ACCO ISO G43 (G4) | 7.00 | 0.28 | 21.30 | 0.84 | 24.40 | 0.96 |
| 7 mm DIN 766 | 7.00 | 0.28 | 22.00 | 0.87 | 23.80 | 0.94 |
| 1/4" ACCO BBB (3B) | 7.14 | 0.28 | 22.10 | 0.87 | 25.20 | 0.99 |
| 8 mm DIN 766 | 8.00 | 0.32 | 24.00 | 0.95 | 27.20 | 1.07 |
| 8 mm ISO 4565 | 8.00 | 0.32 | 24.00 | 0.95 | 28.80 | 1.13 |
| 5/16" ACCO ISO G43 (G4) | 8.40 | 0.33 | 26.20 | 1.03 | 29.70 | 1.17 |
| Lewmar 9.5 mm G40 | 9.50 | 0.37 | 31.50 | 1.24 | 31.60 | 1.24 |
| 3/8" Campbell S4 | 10.00 | 0.39 | 29.00 | 1.15 | 35.00 | 1.30 |
| 10 mm ISO 4565 | 10.00 | 0.39 | 30.00 | 1.18 | 36.00 | 1.42 |
| 3/8" Campbell S3 | 10.00 | 0.37 | 35.00 | 1.36 | 34.00 | 1.31 |
| 10 mm DIN 766 | 10.00 | 0.39 | 28.00 | 1.10 | 36.00 | 1.42 |
| 3/8" ACCO ISO G43 (G4) | 10.00 | 0.39 | 31.00 | 1.22 | 35.00 | 1.38 |
| 11 mm Short Link | 11.00 | 0.43 | 33.00 | 1.30 | 39.00 | 1.54 |
| 11 mm DIN 766 | 11.00 | 0.43 | 31.00 | 1.22 | 40.00 | 1.58 |
| 7/16" ACCO ISO G43 (G4) | 11.80 | 0.45 | 35.50 | 1.40 | 40.10 | 1.58 |
| Lewmar 12 mm G30 / G40 12 mm Short Link (G4) | 12.00 | 0.47 | 36.00 | 1.42 | 40.50 | 1.59 |
| 13 mm DIN 766 | 13.00 | 0.51 | 36.00 | 1.42 | 47.00 | 1.85 |
| 1/2" ACCO ISO G43 (G4) | 13.20 | 0.52 | 40.40 | 1.59 | 45.70 | 1.80 |
| Lewmar 14 mm G30 / G40 14 mm Short Link | 14.00 | 0.55 | 42.00 | 1.65 | 49.00 | 1.93 |
| 14 mm DIN 766 | 14.00 | 0.55 | 41.00 | 1.61 | 50.00 | 1.97 |
| 14 mm Studlink | 14.00 | 0.55 | 56.00 | 2.21 | 50.40 | 1.98 |
| 16 mm Short Link | 16.00 | 0.63 | 48.00 | 1.89 | 56.00 | 2.21 |
| 16 mm DIN 766 | 16.00 | 0.63 | 45.00 | 1.77 | 58.00 | 2.28 |
How does chain match to a windlass gypsy?
Your windlass gypsy (chainwheel) is cut for a specific chain standard and size. Using a chain whose P or W is off — even by a millimeter — causes skipping, jamming or slipping under load. When replacing chain, either match the exact standard your gypsy was cut for, or confirm the gypsy that suits your new chain. Also match the chain's working load to your anchor and boat size so the rode is balanced end to end.
Which chain material and grade should I choose?
Hot-dip galvanized chain is the workhorse choice: economical, tough and easy to re-galvanize when the coating wears. High-test grades such as G40/G43 (G4) offer a higher working load than standard-grade chain of the same diameter, which lets some boats carry a lighter rode without giving up strength. Stainless steel chain costs more but resists corrosion, runs cleanly through the gypsy and stays presentable on deck — a popular upgrade for cruisers who anchor often.
Whatever the material, the rule is the same: the link geometry (D, P and W) must match your gypsy, and the chain's working load must suit your anchor and boat.
What if I can't identify my chain?
MAURIPRO carries calibrated anchor chain in DIN, ISO, ACCO and G4 standards, plus matching gypsies and rode hardware. Not sure which chain fits your windlass? Send us your D, P and W measurements — or simply your windlass model — and our team will confirm the correct chain before you order.
Frequently asked questions
How do I know which anchor chain fits my windlass?
Measure the link diameter (D), inside pitch (P) and inside width (W) of your chain and match all three to a chain standard (DIN, ISO, ACCO or G4). Two chains of the same nominal size can differ in P and W, and those differences determine whether the chain seats correctly in the gypsy.
What do D, P and W mean on a chain dimensions chart?
D is the link (wire) diameter, P is the link pitch (inside length of one link) and W is the inside link width. Windlass gypsies are cut to specific D, P and W values, so all three must match for the chain to feed correctly.
Can I use a different chain standard than my windlass was made for?
Only if the link geometry matches. A gypsy cut for one standard (for example DIN 766) may skip or jam on a chain of the same nominal size but different pitch or width — either match the exact standard or fit a gypsy that suits your new chain.
Is chain diameter enough to choose the right chain?
No. Chains of the same diameter can have different pitch (P) and width (W) depending on the standard, so you must match all three dimensions for the chain to seat and feed correctly in your windlass gypsy.
What is the difference between DIN 766 and ISO 4565 chain?
Both are metric calibrated standards, but pitch and width differ at some sizes — for example 6 mm DIN 766 has an 18.5 mm pitch while 6 mm ISO 4565 has an 18.0 mm pitch and a wider link. A gypsy cut for one will not necessarily accept the other.
What if I can't identify my existing chain?
Measure the D, P and W of a single link and compare them to the chart above, or send those three measurements (and your windlass model) to MAURIPRO and we'll identify the standard and confirm a compatible replacement chain and gypsy.
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