Choosing the right anchor isn’t just about boat length—it’s about understanding how your vessel behaves in real-world conditions and ensuring your anchoring system is ready for anything. Rocna’s anchor sizing approach is based on conservative, experience-driven principles—designed to give you confidence even in the harshest environments.
Here’s everything you need to know about selecting and setting up the correct Rocna anchor for your boat.
Rocna’s Sizing Philosophy #
Rocna anchor sizing is more conservative than most manufacturers. Our recommendations are based on a realistic worst-case scenario: 50 knots of wind, moderate holding seabeds, and adequate scope. These are the kinds of conditions experienced in high-latitude cruising zones like Patagonia, Greenland, or the Southern Ocean—places where failure isn’t an option.
This approach means a Rocna anchor sized for your vessel will often be larger than those recommended by other brands, and for good reason: it’s designed to hold, not just in ideal conditions, but when it really counts.
How to Use the Rocna Sizing Charts #
Rocna sizing charts match two key variables:
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LOA (Length Overall) of your vessel
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Loaded displacement (weight)
To choose the correct anchor:
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Find your boat’s LOA in the left column.
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Move across to the right until you reach the cell that matches or exceeds your vessel’s fully loaded displacement.
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The anchor size in that cell is your recommended Rocna model.
Note: Always select the heavier displacement range if your vessel falls between categories.
The Rocna MK-II maintains the same sizing and vessel compatibility as the Rocna Original and Vulcan anchors. In some cases, improved holding performance allows for increased displacement capacity at the same anchor size.
You can also use our anchor selector tool which will recommend the anchor options for you based on your inputs into the tool.
Multihulls and Special Cases #
The sizing chart is based on monohull designs. For multihulls, we recommend increasing anchor size by up to 50% (typically one model up) to account for higher windage and reduced yaw damping.
For boats heavier or larger than the Rocna 110 can accommodate, classification rules may apply (see below).
What About Secondary Anchors? #
Secondary or stern anchors are often needed for specific maneuvers or redundancy. These don’t always need to be the same size as your primary anchor. We typically recommend choosing one size down from your primary anchor, unless you plan to rely on it frequently or in heavy conditions.
Should I Oversize My Anchor? #
You can—but in most cases, you don’t need to. Rocna anchors already offer a substantial performance margin. Many customers choose to size up when switching from older anchors, but our standard recommendations already account for difficult conditions.
Exceptions where oversizing may help:
Short-scope anchoring (e.g., 2:1 scope in tight anchorages)
Poor-holding seabeds like hardpan, coral, or solid rock
Dead-weight anchoring where the anchor cannot penetrate (friction-only scenarios)
Keep in mind: oversizing too much can introduce practical problems like retrieval difficulty or bow roller incompatibility.
Matching to Your Anchoring System #
Upgrading to a Rocna may reveal weaknesses in your existing anchoring setup. Because Rocna holds so effectively, ensure your:
Chain and rode are appropriately rated
Windlass and bow roller can handle the anchor’s weight and shank profile
Deck hardware is reinforced to manage higher loads
This could be a great opportunity to review your full ground tackle for safety and performance.
Sizing for Classification Standards #
Some vessels—particularly larger commercial or offshore yachts—may require classified anchoring systems that meet specific regulatory standards (such as ABS, RINA, or MCA). These requirements typically use an Equipment Number (EN) formula that considers factors like vessel length, beam, displacement, and windage.
Rocna anchors are designed and manufactured to exceed the performance expectations of Super High Holding Power (SHHP) anchors. While not all sizes currently carry active classification certificates, Rocna anchors:
Have historically been certified by RINA for models from 10 kg through 110 kg. Our manufacturing process and materials remain unchanged, and as such consider these anchors to still meet RINA standards.
Have been ABS-certified on select anchor models, confirming compliance with key classification benchmarks.
Consistently outperform competitors in real-world holding power and reliability—delivering Working Load Limits (WLL) and Breaking Load Limits (BLL) similar or higher relative to other anchor types in the same weight class..
Customers continue to choose Rocna for its proven design, robust manufacturing, and holding strength—even in challenging conditions.
For vessels requiring classified anchors beyond the Rocna 110, we recommend consulting the relevant authority or your naval architect.
Key Takeaways #
Rocna anchors are sized for the poorest of conditions compared to industry norms to give peace of mind in all conditions.
Use LOA and full displacement to select your anchor from our sizing chart.
Consider sizing up for multihulls, short scopes, or difficult bottoms—but in most cases, our recommended size is more than enough.
Review your entire ground tackle system when upgrading to Rocna to ensure it can handle the loads your new anchor delivers.
Still unsure about sizing? Contact us with your vessel specs—we’re happy to help.