Anchor Chain Size Chart & Guide (mm and inch)
Use this anchor chain size chart to find the right chain diameter for your boat. Find your boat length and displacement, read across for the size in millimetres and inches, then check the Muir windlass built for it. Heavy or high-windage boats should go up one size.
Anchor chain size by boat length
Find your boat's length and displacement, then read across for the recommended chain size in millimetres and inches, and the Muir windlasses and drum winches built for it. If your boat is heavy, has high windage or sits at the top of a band, go up a size.
| Vessel Length Profile | Vessel Displacement | Chain Size (Metric) | Chain Size (Imperial) | Weight (DIN 766) | Compatible Muir System |
|---|---|---|---|---|---|
| Up to 6m (20ft) | Under 1,500 kg | 6 mm | 1/4 in | 0.8 kg/m | DW06Storm VR600 |
| 6m – 10m (20 – 33ft) | Under 4,000 kg | 8 mm | 5/16 in | 1.4 kg/m | DW08DW10Storm VR/VRC850 |
| 10m – 13m (33 – 43ft) | Under 8,000 kg | 10 mm | 3/8 in | 2.2 kg/m | DW12Storm VR/VRC1250HR1600 Cougar |
| 13m – 18m (43 – 60ft) | Under 15,000 kg | 13 mm | 1/2 in | 3.9 kg/m | Storm VR/VRC2500HR2500 CheetahHR3500 Jaguar |
| 18m – 24m (60 – 80ft) | Under 30,000 kg | 16 mm | 5/8 in | 5.8 kg/m | HR4000 ThorHR4200 Thor |
Chart revised September 2026. Weights are for DIN 766 calibrated chain. 7 mm and 12 mm chain also fit selected Muir gypsies: check yours with the Windlass Selection Tool.
How to measure anchor chain size
Anchor chain is sized by the diameter of the steel it is made from (the wire diameter), not by the size of the link.
- Clean a few links and measure the wire diameter with vernier calipers. That is the nominal size: 6 mm, 8 mm, 10 mm and so on.
- Measure the inside length (pitch) over three or more links and divide by the number of links. Pitch is what separates DIN 766, ISO 4565, BBB and High Test chain of the same size.
- Compare both figures with the standards, or measure your chain in the Chain Identifier.
How much anchor chain do I need?
Carry enough rode to anchor at a safe scope in the deepest water you normally use. Scope is the length of rode let out divided by the water depth plus the height of your bow roller. A common rule of thumb is at least 5:1 for an all-chain rode, more in strong wind, and around 7:1 for a rope-and-chain rode.
| Depth + bow height | All chain (5:1) | Rope and chain (7:1) |
|---|---|---|
| 5 m | 25 m | 35 m |
| 10 m | 50 m | 70 m |
| 15 m | 75 m | 105 m |
| 20 m | 100 m | 140 m |
Then check your windlass can lift it: the Windlass Selection Tool adds up your chain and anchor weight and checks each model against Muir’s 3× pull rule.
Scope guidance is a general rule of thumb. Allow more in poor holding ground or strong wind, and follow local seamanship advice.
Why Short Link Anchor Chain Matters
When running an automated windlass or drum winch, standard commercial chain will not suffice. Modern marine gypsies are machined to grip a precise link pitch and diameter, so only calibrated short link anchor chain seats correctly in the gypsy — the wrong profile will slip, jump, or jam under load.
Match your boat's length and displacement to a calibrated chain standard (DIN 766 or ISO 4565), then confirm gypsy compatibility before you buy. Use the size chart above to find your size.
Critical Matching Factors
1. Link Calibration: Ensure your chain is certified to DIN 766 or ISO 4565 before installation.
2. Material Grade: Grade 50 (High Tensile) provides exceptional strength-to-weight ratios for performance yachts.
3. Storage Depth: Deep lockers suit vertical windlasses; if the locker is shallow or there is none, a drum winch stores the rode instead.
4. Gypsy Compatibility: Confirm your chain's size and standard match the windlass gypsy designation exactly — the correct diameter in the wrong standard will still slip or jump under load.
DIN766 Standard
The most widely used calibrated short-link standard in Europe and Australia, with a shorter link pitch than ISO 4565.
ISO4565 Standard
An international calibrated short-link standard. Its link pitch and width differ slightly from DIN 766, so a gypsy cut for one may not suit the other. Check the stamp on your chain before you order a gypsy.
Grade 50 / G50
Grade 50 (G50) is a higher-strength calibrated chain than standard Grade 30, giving a higher working load for the same size. Most windlass chain is hot-dip galvanised for corrosion protection.
Anchor Chain Size FAQs
Quick answers to the most common questions about selecting, sizing and matching short link anchor chain for your vessel.
What size anchor chain do I need for my boat?
What is the difference between DIN766 and ISO4565 chain?
Can I use ordinary galvanised chain with a windlass?
How do I identify my existing chain?
Need Help Using This Anchor Chain Size Guide?
If your boat or chain isn't covered here, send us your boat length, displacement and current chain, and Muir's technical team will recommend the right chain and windlass.