Anchor Chain: Grades, Sizing, and Length

Anchor Gear · Ground Tackle

The choice between all-chain and rope-chain combinations is one of those debates that splits cruising sailors by experience level. New cruisers often choose rope-chain because it is lighter and easier to handle by hand. Experienced offshore sailors almost universally use all-chain. The difference in opinion is not random — it reflects a difference in the kind of sailing being done and the conditions being prepared for.

All-Chain vs. Rope-Chain Rodes

An all-chain rode has four advantages over rope-chain that compound in rough weather. First, chain's weight creates catenary — the sag in the rode that absorbs the shock loads of a boat jerking at anchor in a seaway. A rope rode under load straightens out and transmits every wave-induced snatch directly to the anchor; chain hangs in a curve that must be pulled straight before maximum load reaches the anchor shank, giving the boat time to absorb the energy. Second, chain is abrasion-resistant in a way that rope is not. Dragging across coral, barnacled rock, or a rough sandy bottom that rope cannot survive, chain handles without damage. Third, chain sets the anchor more reliably — its weight keeps the shank flat on the bottom, maintaining the correct load angle for the anchor to dig rather than pull free. Fourth, chain requires no leader splice, no chain-to-rope connection fitting, and no worries about the transition zone working loose at the worst possible moment.

The case for rope-chain is weight and cost. Two hundred feet of 3/8-inch G43 chain weighs approximately 175 pounds. Two hundred feet of nylon rope-with-chain-leader weighs a fraction of that. For a smaller coastal boat with no windlass, that weight on the bow — placed as far forward as possible from the boat's pitching axis — has real consequences for motion comfort and sailing performance. For day-sailing and weekend cruising with a kedge in protected anchorages, a 30-foot chain leader on a nylon rode is genuinely adequate. For extended offshore sailing or liveaboard use, the all-chain rode's advantages in storm conditions and abrasion resistance make it the standard choice, and the weight penalty gets managed through careful locker placement rather than eliminated.

Chain Grades Explained

Chain is sold in grades that reflect its yield strength relative to its cross-sectional area. The grades commonly found in marine chandleries are G30, G40 BBB, G43 high-test, and occasionally G70 transport.

G30 Proof Coil is the baseline. It is inexpensive, widely available at hardware stores, and adequate for mooring pennants and light kedge applications. Its working load limit per given diameter is the lowest of the commonly available grades. Using G30 as a primary anchor rode is not wrong, but it means accepting more weight for equivalent strength compared to higher-grade options.

G40 BBB (short-link chain, also called triple BBB) was the traditional offshore anchoring standard for much of the twentieth century. It is stronger per diameter than G30, links are shorter and more consistent in pitch than proof coil, and it feeds through windlass gypsies reliably. Many older boats and windlasses were sized for BBB chain specifically.

G43 High-Test is the current offshore standard and the grade most recommended by experienced cruising sailors who have evaluated the options. G43 chain is approximately 40% stronger per pound than G30 proof coil of the same diameter — which means you can carry a smaller/lighter chain for the same working load limit, or carry the same weight and gain a substantial strength margin. A 5/16-inch G43 has a working load limit roughly equivalent to 3/8-inch G30. For most boats, this means one step down in chain diameter, which translates directly to a lighter anchor locker and better sailing performance. G43 is manufactured to tighter tolerances than proof coil, which also means more consistent gypsy fit on calibrated windlasses.

G70 Transport Chain is the yellow-chromate-coated chain commonly seen on flatbed trailers and in farm supply stores. It is very strong — stronger per weight than G43 — but it is brittle under cyclic fatigue loading. Anchoring subjects chain to exactly the kind of repeated load cycles that exploit this brittleness. G70 has failed in anchoring applications with enough regularity that it is broadly advised against by the cruising community, regardless of its impressive static strength figures.

Sizing by Boat LOA

The standard guidance from windlass manufacturers, anchor manufacturers, and cruising publications converges on a straightforward table by boat length overall, assuming G43 high-test chain:

Boats under 35 feet: 5/16-inch G43. This is a light, manageable chain that provides more than adequate holding power for boats in this size range. At coastal use weights, the 5/16 rode is hand-haul-able in a pinch if the windlass fails.

Boats 35–45 feet: 3/8-inch G43. The standard offshore choice for the majority of blue-water cruising boats. The weight is significant — 175 lbs for 200 feet — but manageable with a properly sized electric windlass and a well-placed anchor locker.

Boats 45 feet and larger: 7/16-inch G43. Heavier displacement at this length means higher windage and more load on the anchor system in storm conditions. The step up to 7/16 provides the working load margin that larger boats require.

Displacement should adjust these numbers. A heavy, full-keel 38-footer at 28,000 pounds carries more windage and scope-load than a lightweight 42-footer at 14,000 pounds. When boat displacement is substantially above the median for its length, move up a chain size.

How Much Chain to Carry

The minimum for coastal sailing — weekend trips, known anchorages, modest weather expectations — is 200 feet of chain. This allows a 7:1 scope (the minimum for serious holding in 25-foot depth) with enough reserve to deal with rising tide. Two hundred feet disappears quickly: 25 feet of depth at high water plus 5 feet of freeboard means 30 feet of height — at 7:1 scope, that consumes 210 feet. In anything over 30 feet of water, 200 feet becomes a constraint.

For liveaboard use or any offshore passage-making: 300 feet minimum. Many experienced offshore sailors carry 400 feet, accepting the weight penalty for the ability to anchor in 40–50 feet of water with proper scope, or to deploy extra chain in severe weather. The World ARC and ocean rally guidance for participating boats typically calls for 300 feet of chain as a minimum; boats with 400 feet are considered better-prepared.

The Windlass Gypsy Compatibility Problem

Windlass gypsies — the sprocket that drives chain — are machined to a specific chain pitch (the center-to-center distance between links) and wire diameter. A gypsy designed for BBB chain will not reliably feed G43 chain of the same diameter, because the link geometry differs. G43 links are longer in proportion to their diameter than BBB links, and the gypsy pockets are machined to match. Feeding the wrong chain through a gypsy causes jamming, skipping, and in serious cases, damage to the gypsy or chain.

Before buying chain, confirm the chain specification (DIN 766 is the most common standard for marine anchor chain) and pitch against your windlass manufacturer's specification. If replacing an older windlass that was matched to BBB chain, either replace the gypsy or replace the windlass. This is not a detail that can be ignored — a jammed gypsy in a deteriorating anchorage at night is a crisis.

Swivel or No Swivel

The debate about whether to use a swivel between chain and anchor shank has been running in cruising forums for decades without resolution, which is itself informative. The argument for a swivel: as the boat swings through multiple tidal and wind cycles, the chain twists; a swivel allows it to unwind without transmitting torque to the anchor. The argument against: swivels are the weakest link in the ground tackle system unless rated to exceed the working load limit of the chain, and most of the swivels sold in chandleries are not.

The practical consensus among experienced offshore sailors leans toward no swivel, or a rated swivel with a working load limit clearly documented to exceed the chain's WLL. Many sailors connect anchor shank directly to chain with a galvanized shackle with the pin moused (secured with wire or seizing wire through the hole in the pin) — simple, strong, and free of failure modes. If you choose a swivel, buy a rated one from a reputable manufacturer, verify the load rating against your chain's WLL, and inspect it every season.

Connecting Links and Shackles

The chain-to-anchor connection deserves the same attention as chain grade selection. A galvanized screw-pin anchor shackle rated to exceed the chain's WLL, with the pin moused with seizing wire, is the most reliable and universally understood option. Mouse the pin — thread seizing wire through the hole in the pin and around the bow of the shackle — so that vibration cannot back the pin out. A 3/8-inch anchor shackle rated at 2 tons working load costs a few dollars; an unmoused pin backing out at 0300 in an anchorage costs much more.

Connecting links (the pear-shaped connecting links sometimes used to join chain runs) are adequate if rated correctly, but they are harder to inspect quickly and easier to forget. Many offshore sailors prefer shackles for visibility — you can see at a glance whether the pin is moused and whether the fitting shows signs of wear or corrosion.

The Weight Penalty and Locker Placement

Two hundred feet of 3/8-inch G43 chain weighs approximately 175 pounds. Three hundred feet weighs around 265 pounds. This weight, concentrated in the anchor locker at the bow, is at the worst possible location for pitching motion — as far as possible from the center of the boat's pitching axis. In a seaway, bow-heavy boats hobby-horse: they pitch more than necessary, which wears the crew, reduces speed, and increases green-water risk.

The mitigation is locker placement. The ideal anchor locker is as close to amidships as possible while still allowing the chain to run cleanly to the bow roller — which usually means as far aft in the bow section as the deck layout permits. Chain should pile in the locker as centrally as possible, not jammed into the very tip of the bow. Some production boats have anchor lockers positioned for appearance (symmetrical with the deck) rather than for weight distribution; on these boats, it is worth considering whether a portion of the chain rode can be stowed farther aft in a secondary bag or locker.

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Frequently Asked Questions

What size G43 high-test chain should a 40-foot cruising boat carry? A 40-foot boat in the 35–45 ft range should use 3/8-inch G43 high-test chain as its standard. G43 high-test is the offshore standard because it offers roughly twice the working load limit of Grade 30 proof coil at the same diameter, meaning you can carry less weight for the same strength.

How much anchor chain is needed for coastal versus offshore cruising? The minimum for coastal cruising is 200 feet of chain, while offshore cruisers should carry at least 300 feet. The additional 100 feet provides the deeper-water scope and emergency reserve needed when anchoring in unfamiliar or deep anchorages far from assistance.

Why does chain diameter need to match the windlass gypsy? The gypsy (windlass drum) is machined for a specific chain diameter and link profile — typically the DIN 766 standard for most European windlasses. Using mismatched chain causes the links to skip, jam, or load the gypsy unevenly, which can damage both the windlass and the chain under load.

How heavy is 200 feet of 3/8-inch G43 chain? 200 feet of 3/8-inch G43 chain weighs approximately 175 pounds. This weight is significant in bow trim and sail balance, which is why offshore cruisers should stow the majority of their chain as far aft as possible in the chain locker to minimize the weight's effect on pitching.

What is the main advantage of G43 high-test over Grade 30 proof coil for offshore use? G43 high-test chain offers approximately twice the working load limit of Grade 30 proof coil of the same diameter, allowing sailors to use lighter, smaller-diameter chain for equal strength. The weight savings on 300 feet of chain are meaningful, directly reducing bow-down trim and improving sailing performance.