The Complete Anchor Rope & Chain Sizing Guide
The 30-second answer
Boat length sets your rope diameter, rope diameter sets the chain size that goes with it, and water depth sets how much of both you carry. For boats from 30 to 45 ft we stock ready-made kits in both finishes. Above that we build the rode to length instead.
Boats 30 to 38 ft1/2 in rope, 1/4 in chainFrom $166.09
Our deepest range, in galvanized and 316 stainless, from 100 ft up to 300 ft of rode. The 200 ft kit suits most mid-size cruisers.
Boats 38 to 45 ft9/16 in rope, 5/16 in chainFrom $250.58
A step up in both rope and chain for heavier cruisers and boats carrying more windage. Stocked from 150 ft through 300 ft.
Boats 45 ft and over5/8 in rope, 3/8 in chainMade to length
Above 9/16 in we build the rode to your boat rather than stocking it. Tell us the length and the depth you anchor in.
Anchor rope and chain size chart
Find your boat length on the left and read across. Rope and chain diameter follow from the load your boat puts on the rode. Length is a separate question, and it depends on how deep you anchor, at seven times that depth.
| Boat length | Rope diameter | Chain diameter | Chain length | Total rode at 7:1 |
|---|---|---|---|---|
| Up to 25 ft (7.6 m) | 3/8 in | 1/4 in | 15 to 20 ft | 150 ft |
| 25 to 30 ft (7.6 to 9 m) | 3/8 to 1/2 in | 1/4 in | 20 to 25 ft | 150 to 200 ft |
| 30 to 38 ft (9 to 11.6 m) | 1/2 in | 1/4 in | 25 to 30 ft | 200 ft |
| 38 to 45 ft (11.6 to 13.7 m) | 9/16 in | 5/16 in | 35 to 40 ft | 200 to 250 ft |
| 45 to 55 ft (13.7 to 16.8 m) | 5/8 in | 3/8 in | 45 to 50 ft | 250 to 300 ft |
| 55 ft and over (16.8 m+) | 3/4 in | 3/8 to 1/2 in | 55 ft and over | 300 ft and over |
Highlighted rows are sizes we carry as ready-made kits, listed with prices further down. Heavier displacement and high-windage boats such as flybridges and deep-draft cruisers should size up one row from their length bracket.
What scope is, and why it decides the length
Scope is the ratio between how much rode you let out and how deep the water is. The depth that counts is measured from your bow roller to the seabed, not from the waterline, so add your freeboard. Anchoring in 10 ft of water with 3 ft of bow height means your true depth is 13 ft.
The reason it matters is angle. Pull straight up on an anchor and it breaks out almost at once. Pull it sideways, low and close to the seabed, and it digs in harder the more you pull. A longer rode flattens that angle, which is the whole job.
For a rope and chain rode, work to at least 7:1. That is seven feet of rode for every foot of true depth, which is where the 200 ft and 250 ft kits come from for boats anchoring in 25 to 35 ft of water. All-chain rodes get away with 4:1 or 5:1 because the weight of the chain itself sags into a curve, called the catenary, that keeps the pull low without needing the extra length.
Why every rode has a length of chain on the end
The chain nearest the anchor does two jobs that rope cannot. It puts weight exactly where you need the pull to stay horizontal, and it takes the abrasion from rock, coral and shell that would chafe through nylon in a season.
Rope does the rest of the job better than chain would. It is lighter on the bow, it is easier to handle, and nylon stretches under load, which absorbs the snatch loads that would otherwise come straight through to your cleats and your anchor.
1/2 in rope with 1/4 in chain, for boats 30 to 38 ft
This is the most common combination on the water and the one we carry in the most depth. Every kit below pairs 1/2 in three-strand nylon with 15 ft of 1/4 in G4 chain unless noted.
| Rode length | Galvanized chain | 316 stainless chain |
|---|---|---|
| 100 ft | $166.09 | $252.79 |
| 150 ft | $191.93 | $285.34 |
| 200 ft | $221.17 | $309.00 |
| 250 ft | — | $333.37 |
| 300 ft | — | $391.93 |
There is also a 100 ft kit with a shorter 10 ft stainless chain at $158.60, which suits shallow-water anchoring where you want the stainless finish without paying for chain you will not use.
9/16 in rope with 5/16 in chain, for boats 38 to 45 ft
Stepping up to 9/16 in rope adds strength and stretch for heavier cruisers, paired with 5/16 in chain for the extra margin at the anchor end. Every kit here carries 20 ft of chain unless noted.
| Rode length | Galvanized chain | 316 stainless chain |
|---|---|---|
| 150 ft | $250.58 | $415.73 |
| 200 ft | $275.57 | $485.86 |
| 250 ft | $324.02 | $502.94 |
| 300 ft | $373.15 | $519.26 |
If you anchor over rough ground and want more chain in the water, the 250 ft kit with 25 ft of stainless chain is $580.38.
Galvanized or 316 stainless
Hot-dip galvanized chain is the practical choice and it is what most cruisers run. The zinc coating corrodes in place of the steel underneath, which buys years of service. When it finally wears through, you regalvanize or replace it at a fraction of the stainless price.
316 stainless costs more and buys you two things. It does not stain the topsides or leave rust marks down the bow, and it matches the rest of your stainless deck hardware. On boats where the bow is on show, that matters enough to justify the difference.
Whichever finish you pick, the number that has to be right is the chain diameter. A windlass gypsy is cut to one chain size and one pitch, and chain that is even slightly off spec will ride up the teeth and jump under load. Check your windlass spec sheet before you order, and if you are still choosing the machine itself, our guide to how to choose the right windlass works through gypsy matching in detail.
Outside these sizes?
For 3/8″ or 5/8″+ rope-chain combinations, get in touch and we’ll quote a custom-length rode. Tell us your boat length and the depth you usually anchor in and we will come back with a price.
If your boat has no usable anchor locker, the rode question changes completely, because a drum winch carries the whole rode on itself. That comparison is in drum winch vs windlass.
Frequently asked questions
What size anchor rope do I need for a 35 ft boat?
A 35 ft boat sits in the 30 to 38 ft bracket, which takes 1/2 in three-strand nylon with 1/4 in chain. Carry around 200 ft of total rode, which covers anchoring in about 28 ft of water at 7:1 scope.
How much chain should I have on a rope rode?
Between one and one and a half boat lengths is the common rule, and our kits follow it: 15 ft of chain on the 1/2 in kits and 20 ft on the 9/16 in kits. The chain keeps the pull horizontal and takes the abrasion on the bottom, so more of it helps on rough ground.
What does 7:1 scope actually mean?
Seven feet of rode let out for every foot of depth, measured from your bow roller down to the seabed rather than from the waterline. In 20 ft of water with 3 ft of freeboard you would let out 161 ft, so a 200 ft rode gives you working room.
Should I choose galvanized or stainless chain?
Galvanized for value and service life, stainless for appearance and no rust staining on the topsides. Both are G4 grade and both hold the same load. The difference is finish and price, not strength.
Does the chain size have to match my windlass?
Yes, and this is the one thing you cannot approximate. The gypsy is machined for a single chain diameter and pitch. Chain that is close but not correct will slip, ride up the teeth or jam under load, so check the spec sheet for your machine before ordering.
Can I use eight-plait rope instead of three-strand?
Eight-plait stows flatter in a shallow locker and runs well over a gypsy, and three-strand is easier to splice and cheaper. Our kits are three-strand nylon. If your locker is tight enough that stowage is the binding problem, a drum winch may suit the boat better than either rope.
Why is the rope spliced to the chain rather than shackled?
A shackle will not pass over a bow roller or through a windlass gypsy without catching. A tapered splice keeps the diameter even through the join so the rode runs continuously, which is why every kit we sell comes spliced.
How long does anchor rope last?
Nylon loses strength to ultraviolet and to the repeated stretching that makes it useful in the first place. On a boat anchoring regularly, five to seven years is a fair working life. Inspect the first 30 ft nearest the chain most closely, since that section takes the most load and the most abrasion.
Not sure which kit fits your boatSend us your boat length, the depth you usually anchor in and the chain size your windlass takes. We will tell you which rode to run and which kit to buy.
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