Choosing the right size of anchor chain is very important for the safe use of ships and the smooth progress of engineering projects. Many buyers get confused by the complex parameters when purchasing anchor chains or doing early research for a project. The wrong size of anchor chain can cause unstable anchoring, shorten its service life, and increase project cost and risk.
Based on many years of experience in anchor chain production, Tuohai has prepared a practical guide with detailed tables and a free sizing calculator to help you quickly find the right size of anchor chain.
Basic Concept of Anchor Chain Size
The size of an anchor chain has three primary parameters: bar diameter (d), pitch (P), and inside width (B).
- Bar diameter (d): The diameter of the steel wire used to make the anchor chain, which decides the strength and WLL of the chain.
- Pitch (P): The distance between the links. For stud link chains, it is about 6 × d; for studless chains, it is a bit longer, about 6.05 × d.
- Inside width (B): This parameter decides if the chain matches the chain wheel or windlass. For stud link chains, it is about 3.6 × d; for studless chains, it is a bit wider, about 3.8 × d.
Please note that the stud and the studless links are two different anchor chains. Their differences are as follows:
- Stud Link Chain: There is a stud in the middle of each link, which makes the link stronger and less prone to deformation. It is used for large ships, deep-water work, and heavy load environments, such as bulk carriers, tankers, or offshore platforms.
- Studless Link Chain: There is no stud in the middle of the link, and it looks similar to a normal welded steel link chain. It is lighter and more flexible, suitable for small ships, buoys, temporary mooring, or places with limited space.
How to Choose the Size of an Anchor Chain
When choosing a suitable size anchor chain, many factors must be considered. This will help your anchor chain system stay stable and reduce unnecessary wear.
Before choosing the size of the anchor chain, you need to check the following key factors first:
- Vessel Displacement: Also called tonnage. The larger the tonnage, the larger the size and the higher the strength of the anchor chain needed.
- Vessel Type: Different vessel designs and working environments have different needs for anchor chain strength and size, such as bulk carriers, container ships, tankers, yachts, and construction vessels.
| Vessel Type | Typical Displacement | Recommended Chain Diameter (mm) | Notes |
| Bulk Carrier | 10,000 – 50,000 DWT | 52 – 76 mm | Standard Grade 2 or 3 chains, durable and economical |
| Tanker | 50,000 – 150,000 DWT | 68 – 92 mm | High safety margin, consider Grade 3 or R3 |
| Container Ship | 1,000 – 15,000 TEU | 52 – 114 mm | Larger ships require higher diameter and strength |
| Construction Vessel | 3,000 – 15,000 DWT | 52 – 90 mm | Often needs customized sizing for offshore conditions |
| Tugboat | 500 – 3,000 DWT | 26 – 52 mm | Short and heavy-duty chains for frequent operations |
| Ferry / Cruise Ship | 2,000 – 80,000 GT | 36 – 84 mm | Focus on stability and noise reduction |
| Fishing Vessel | < 1,000 DWT | 16 – 36 mm | Lightweight chains, easy to handle |
| Yacht / Pleasure Boat | < 500 GT | 8 – 26 mm | Stainless or galvanized chains preferred |
| Offshore Platform / Mooring Buoy | Project-based | 76 – 162 mm | Heavy-duty chains for extreme durability |
| LNG Carrier / Heavy Lift Vessel | 80,000 – 200,000 DWT | 76 – 122 mm | Must meet highest safety standards |
Note: This table is for general reference only. Actual sizes should be confirmed based on vessel displacement, environmental conditions, and safety margins. For accurate selection, use the Anchor Chain Size Chart and Anchor Chain Sizing Calculator.
- Anchoring Environment: You need to check the water depth, seabed type, wind direction, and prevailing wind of the anchoring environment, as these factors will affect the load on the chain during use.
| Operating Condition | Typical Recommended Diameter(mm) | Notes |
| Port Mooring | 28 – 76 mm | Standard sizes are sufficient for calm and protected waters. |
| Coastal Anchoring | 52 – 84 mm | Slightly larger chains for moderate winds and tidal changes. |
| Offshore Platform Mooring | 76 – 162 mm | Heavy-duty chains for deep water, strong currents, or harsh weather. |
| Buoy Mooring | 16 – 52 mm | Lightweight, flexible chains for easy handling and frequent adjustments. |
| Deepwater Anchoring | 84 – 162 mm | Large diameter chains to handle high tension and long lengths. |
| Temporary Mooring or Standby Operations | 36 – 68 mm | Balanced size for easy handling and adequate holding strength. |
Tip: Always validate the exact size with engineering calculations or use the Anchor Chain Size Chart and Anchor Chain Sizing Calculator for precise matching.
- Weight and Design of Fittings: The anchor chain is used together with other fittings, such as anchors and connecting links. The size and other parameters of the anchor chain need to match these fittings.
In general, for calm waters or ports, the 28–76 mm anchor chains are usually enough. For deep water or rough weather conditions, you should choose larger sizes(84–162 mm) to ensure safety.
In addition, Tuohai has prepared a detailed Anchor Chain Size Chart, which includes diameter, weight, breaking strength, and other key parameters. You can use this chart to quickly match the anchor chain you need.
Download for Free: Anchor Chain Size Chart
How to Choose the Length of Anchor Chain
In addition to the size parameters above, the length of the anchor chain is also a very important factor. In general, the length of the chain is calculated by water depth×scope ratio.
The scope ratio is the proportion of the length of the anchor chain released to the water depth.
The length of the anchor chain is not only related to water depth but also depends on the anchoring environment, wave and wind conditions, seabed type, as well as the size and displacement of the vessel. In general, the deeper the water and the harsher the environment, the longer the chain you need, which can provide stronger holding power.
Here are the recommended anchor chain scope ratios for different conditions for your reference:
| Condition | Recommended Scope Ratio | Notes |
| Port Mooring (Calm Waters) | 3:1 – 5:1 | Suitable for protected waters or sheltered anchorages, shorter chains are usually sufficient. |
| General Anchorage | 5:1 – 7:1 | Standard range for daily anchoring in moderate conditions. |
| Rough Weather or Heavy Seas | 7:1 – 10:1 | Longer chain lengths to ensure safety during strong winds, currents, or prolonged anchoring. |
| Deepwater Anchoring | 8:1 – 12:1 | For deep water or complex seabed conditions, an extra chain length is required. |
| Temporary Mooring or Standby Operations | 4:1 – 6:1 | Balanced length for flexible and short-term mooring operations. |
For Example:
For port anchoring, if the scope ratio is 4 and the total water depth is 10 meters, the required length of anchor chain is:
10×4=40 meters
In rough weather, with the same 10 meters total water depth, the scope ratio may need to be 8, so the required length of anchor chain will be:
10×8=80 meters
Detailed Steps for Anchor Chain Length Calculation
Step 1: Confirm the Water Depth
Check the water depth at the anchoring position, and take into account tidal changes and the vessel’s draft. This ensures the length of the anchor chain is still enough at high tide.
For Example:
If the water depth is 12 meters, the water level rises 2 meters during high tide, and the vessel draft is 3 meters, then the total depth (also called anchoring depth) is:
12+2+3=17 meters
Step 2: Check the Environment and Choose the Right Scope Ratio
Assess the anchoring environment:
- Calm port or sheltered waters
- Moderate waves
- Rough weather or strong currents
- Deep water or pelagic environment
You can select an appropriate ratio by referring to the scope ratio table above.
Step 3: Calculate the Required Anchor Chain Length
The formula is: Chain length = Total water depth × Scope ratio
For example:
If the total water depth is 15 meters, and the scope ratio is 6:1, then the required chain length is
15 × 6 = 90 meters
Step 4: Add a Safety Margin
Depending on the different environments, it is recommended to increase the calculated anchor chain length by 10% to 20% as a safety margin. This helps handle sudden conditions, such as strong currents, frequent swinging, or big tidal changes.
That is:
90 × 1.2 = 108 meters
We have prepared an Anchor Chain Sizing Calculator.
You only need to enter the vessel’s displacement, type, water depth, and anchoring environment. The system will automatically calculate the most suitable chain size and length for your project, greatly reducing errors and time costs caused by manual calculations
Click to Download the Anchor Chain Sizing Calculator for Free
For deep water areas or important engineering projects, it is recommended to consult the marine engineer or classification society, such as LR, DNV, or ABS, for professional advice and confirmation of the required anchor chain size.
FAQs
Common Mistakes When Choosing Anchor Chain Size
When choosing the size of an anchor chain, the following mistakes are very common:
- Only looking at vessel tonnage and water depth, and not thinking about the anchoring environment.
For example, a 50-ton vessel anchoring in a port and in the deep sea needs very different chain sizes and strengths. - The chain grade does not match other fittings.
The holding power of the anchor system depends on the weakest part of the system. The size and grade of the anchor chain must match the other fittings(Bow Shackle, D Shackle, Swivel Shackle, Shackle Pin, etc.), or even be higher, or there will be safety risks.
What are the International Standards and Certifications for Anchor Chains?
International standards:
- ISO 1704:2007 – Ship Anchor Chain
Defines the size and mechanical properties of Stud Link and Studless Link anchor chains and mooring chains. - IACS UR W18 – Unified Requirements
The basis used by classification societies (ABS, LR, DNV, CCS, etc.) when certifying anchor chains. - OCIMF – Technical reference for special conditions such as tankers and offshore platforms.
Class Certifications:
- LR (Lloyd’s Register)
- ABS (American Bureau of Shipping)
- DNV (Det Norske Veritas)
- BV (Bureau Veritas)
- CCS (China Classification Society)
Other national standards:
- China: GB/T 549
- USA: ASTM / ABS
- Japan: JIS F3303
These standards and certifications make sure the anchor chains from different countries and suppliers have the same size, strength, and safety.
What are the Anchor Chain Grades?
Anchor and Mooring Chain There are different grades of anchor chain/mooring chain that indicate strength and the most appropriate use:
Grade 1 (G1):
This is the smallest strength, for small open boats and fishing smacks. Cheaper but less durable.
Grade 2 (G2):
Medium strength, very common. One of its uses is mooring for merchant ships and general port operations. Fairly balanced in terms of cost and performance.
Grade 3 (G3):
High strength, approximately 20–30% stronger than Grade 2. Ideal for the big merchant ships, deeper water, and more complicated conditions.
R3 / R3S / R4:
Higher strength than G3. Applied areas: offshore platforms, deep sea projects, FPSOs, and mooring buoys. Meets very high safety standards and is more expensive.
Custom Grades:
Built for specialized engineering projects or very large platforms. Typically classed under LR, DNV, or ABS.
How to Quickly Calculate the Required Anchor Chain Size and Length?
Use our Anchor Chain Sizing Calculator. Enter the vessel’s displacement, water depth, and anchoring condition to quickly get the recommended size and length, avoiding the trouble and mistakes of manual calculation.
How Often Should Anchor Chains Be Checked or Replaced?
Daily Check: It is recommended to visually inspect the anchor chain before and after each anchoring. Check for wear, rust, or dimensional changes.
Regular Maintenance: A full check should usually be done every 6 months or during yearly maintenance.
Replacement Cycle: Depending on how often it is used and the sea conditions, a full inspection or replacement is usually needed every 5–7 years.
How to Make the Anchor Chain Last Longer?
- Choose the right size of anchor chain to avoid a mismatch with other equipment and reduce friction.
- Choose the right surface treatment, such as hot-dip galvanizing or professional anti-corrosion coating.
- In high-salt or strong-corrosion areas, wash the anchor chain often and apply protective grease.
- Check the chain links and fittings for wear regularly and replace old parts in time.
Can Anchor Chain Size be Customized for Engineering Projects?
Yes. We support custom anchor chains in full sizes from 12.5 mm to 162 mm. The material grade, length, surface treatment, and certification can also all be adjusted based on your project needs.
For related product details and practical comparisons, you can also read about G4 vs G43 Chain: Key Differences and Typical Applications, Your Trusted Stainless Steel Chain Supplier, and Marine Anchor Chain.
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