Rocna Anchors Sizing Guide

There’s a Rocna Original, Rocna Mk II, or Vulcan anchor to suit just about any vessel – including larger sizes not featured here. To choose the correctly sized Rocna or Vulcan anchor for your boat, follow the chart and instructions.

Anchor Sizing Guide

For Multihulls: use the chart as instructed, then select the model one size larger.

Use the tabs to navigate between Metric Tonnes (t), Short Tons (T), and Pounds (lb).

Rocna Original & Vulcan

469101215202533405570110
VesselLengthVulcan onlyRocna Orig. onlyVulcan onlyRocna Orig. onlyRocna Orig. only
4 m13 ft≤ 2 t
5 m16 ft≤ 1 t≤ 5 t
6 m20 ft≤ ½ t≤ 3.5t≤ 7 t
7 m23 ft≤ ½ t≤ 2 t≤ 6 t≤ 7 t≤ 9 t
8 m26 ft≤ 1 t≤ 5 t≤ 6 t≤ 8 t≤ 12 t
9 m30 ft≤ ½ t≤ 4 t≤ 5 t≤ 7 t≤ 10 t≤ 16 t
10 m33 ft≤ 3 t≤ 4 t≤ 6 t≤ 8.5 t≤ 14 t≤ 22 t
11 m36 ft≤ 2 t≤ 3 t≤ 5 t≤ 7 t≤ 12 t≤ 20 t
12 m39 ft≤ 4 t≤ 6 t≤ 10 t≤ 18 t≤ 30 t
14 m46 ft≤ 4 t≤ 6 t≤ 13 t≤ 23 t≤ 40 t
16 m52 ft≤ 3 t≤ 9 t≤ 18 t≤ 32 t≤ 60 t
18 m59 ft≤ 5 t≤ 14 t≤ 25 t≤ 50 t≤ 85 t
20 m66 ft≤ 10 t≤ 18 t≤ 40 t≤ 75 t≤ 165 t
22 m72 ft≤ 6 t≤ 12 t≤ 33 t≤ 65 t≤ 150 t
24 m79 ft≤ 7 t≤ 25 t≤ 55 t≤ 135 t
26 m85 ft≤ 18 t≤ 45 t≤ 120 t
28 m92 ft≤ 35 t≤ 105 t
30 m98 ftUse EN*
AnchorWeight4 kg6 kg9 kg10 kg12 kg15 kg20 kg25 kg33 kg40 kg55 kg70 kg110 kg
9 lb13 lb20 lb22 lb27 lb33 lb44 lb55 lb73 lb88 lb121 lb154 lb243 lb
SuggestedG40 chain6mm6mm7mm7mm8mm8mm9mm10mm10mm11mm12mm14mm16mm
1/4″1/4″1/4″1/4″5/16″5/16″5/16″3/8″3/8″7/16″7/16″1/2″5/8″
469101215202533405570110
VesselLengthVulcan onlyRocna Orig. onlyVulcan onlyRocna Orig. onlyRocna Orig. only
4 m13 ft≤ 2.2 tn
5 m16 ft≤ 1.1 tn≤ 5.5 tn
6 m20 ft≤ ½ tn≤ 3.9 tn≤ 7.7 tn
7 m23 ft≤ ½ tn≤ 2.2 tn≤ 6.6 tn≤ 7.7 tn≤ 9.9 tn
8 m26 ft≤ 1.1 tn≤ 5.5 tn≤ 6.6 tn≤ 8.8 tn≤ 13.2 tn
9 m30 ft≤ ½ tn≤ 4.4 tn≤ 5.5 tn≤ 7.7 tn≤ 11.0 tn≤ 17.6 tn
10 m33 ft≤ 3.3 tn≤ 4.4 tn≤ 6.6 tn≤ 9.4 tn≤ 15.4 tn≤ 24.3 tn
11 m36 ft≤ 2.2 tn≤ 3.3 tn≤ 5.5 tn≤ 7.7 tn≤ 13.2 tn≤ 22.0 tn
12 m39 ft≤ 4.4 tn≤ 6.6 tn≤ 11.0 tn≤ 19.8 tn≤ 33.1 tn
14 m46 ft≤ 4.4 tn≤ 6.6 tn≤ 14.3 tn≤ 25.4 tn≤ 44.1 tn
16 m52 ft≤ 3.3 tn≤ 9.9 tn≤ 19.8 tn≤ 35.3 tn≤ 66.1 tn
18 m59 ft≤ 5.5 tn≤ 15.4 tn≤ 27.6 tn≤ 55.1 tn≤ 93.7 tn
20 m66 ft≤ 11.0 tn≤ 19.8 tn≤ 44.1 tn≤ 82.7 tn≤ 182 tn
22 m72 ft≤ 6.6 tn≤ 13.2 tn≤ 36.4 tn≤ 71.7 tn≤ 165 tn
24 m79 ft≤ 7.7 tn≤ 27.6 tn≤ 60.6 tn≤ 149 tn
26 m85 ft≤ 19.8 tn≤ 49.6 tn≤ 132 tn
28 m92 ft≤ 38.6 tn≤ 116 tn
30 m98 ftUse EN*
Anchor weight4 kg6 kg9 kg10 kg12 kg15 kg20 kg25 kg33 kg40 kg55 kg70 kg110 kg
9 lb13 lb20 lb22 lb27 lb33 lb44 lb55 lb73 lb88 lb121 lb154 lb243 lb
SuggestedG40 chain6 mm6 mm7 mm7 mm8 mm8 mm9 mm10 mm10 mm11 mm12 mm14 mm16 mm
1/4″1/4″1/4″1/4″5/16″5/16″5/16″3/8″3/8″7/16″7/16″1/2″5/8″
Nb: weights and areas may vary slightly. Vessel displacement units: 1 tn (short ton) = 2,000 lb
469101215202533405570110
VesselLengthVulcan onlyRocna Orig. onlyVulcan onlyRocna Orig. onlyRocna Orig. only
4 m13 ft≤ 4400 lb
5 m16 ft≤ 2200 lb≤ 11000 lb
6 m20 ft≤ 1100 lb≤ 7700 lb≤ 15400 lb
7 m23 ft≤ 1100 lb≤ 4400 lb≤ 13200 lb≤ 15400 lb≤ 19800 lb
8 m26 ft≤ 2200 lb≤ 11000 lb≤ 13200 lb≤ 17600 lb≤ 26500 lb
9 m30 ft≤ 1100 lb≤ 8800 lb≤ 11000 lb≤ 15400 lb≤ 22000 lb≤ 35300 lb
10 m33 ft≤ 6600 lb≤ 8800 lb≤ 13200 lb≤ 18700 lb≤ 30900 lb≤ 48500 lb
11 m36 ft≤ 4400 lb≤ 6600 lb≤ 11000 lb≤ 15400 lb≤ 26500 lb≤ 44100 lb
12 m39 ft≤ 8800 lb≤ 13200 lb≤ 22000 lb≤ 39700 lb≤ 66100 lb
14 m46 ft≤ 8800 lb≤ 13200 lb≤ 28700 lb≤ 50700 lb≤ 88200 lb
16 m52 ft≤ 6600 lb≤ 19800 lb≤ 39700 lb≤ 70500 lb≤ 132300 lb
18 m59 ft≤ 11000 lb≤ 30900 lb≤ 55100 lb≤ 110200 lb≤ 187400 lb
20 m66 ft≤ 22000 lb≤ 39700 lb≤ 88200 lb≤ 165300 lb≤ 363800 lb
22 m72 ft≤ 13200 lb≤ 26500 lb≤ 72800 lb≤ 143300 lb≤ 330700 lb
24 m79 ft≤ 15400 lb≤ 55100 lb≤ 121300 lb≤ 297600 lb
26 m85 ft≤ 39700 lb≤ 99200 lb≤ 264600 lb
28 m92 ft≤ 77200 lb≤ 231500 lb
30 m98 ftUse EN*
Anchorweight4 kg6 kg9 kg10 kg12 kg15 kg20 kg25 kg33 kg40 kg55 kg70 kg110 kg
9 lb13 lb20 lb22 lb27 lb33 lb44 lb55 lb73 lb88 lb121 lb154 lb243 lb
SuggestedG40 chain6 mm6 mm7 mm7 mm8 mm8 mm9 mm10 mm10 mm11 mm12 mm14 mm16 mm
1/4″1/4″1/4″1/4″5/16″5/16″5/16″3/8″3/8″7/16″7/16″1/2″5/8″
Nb: weights and areas may vary slightly. Vessel displacement units: 1 tn (short ton) = 2,000 lb

Rocna MK II

469121520253340506080100
VesselLength
4 m13 ft≤ 2 t
5 m16 ft≤ 1 t≤ 5 t
6 m20 ft≤ ½ t≤ 3.5 t≤ 8 t
7 m23 ft≤ ½ t≤ 2 t≤ 7 t≤ 10 t
8 m26 ft≤ 1 t≤ 6 t≤ 8.5 t≤ 13 t
9 m30 ft≤ ½ t≤ 5 t≤ 7.5 t≤ 11 t≤ 18 t
10 m33 ft≤ 4 t≤ 6.5 t≤ 9.5 t≤ 16 t≤ 25 t
11 m36 ft≤ 3 t≤ 5.5 t≤ 8 t≤ 14 t≤ 23 t
12 m39 ft≤ 4.5 t≤ 6.5 t≤ 11 t≤ 21 t≤ 34 t
14 m46 ft≤ 4.5 t≤ 7 t≤ 15 t≤ 26 t≤ 45 t
16 m52 ft≤ 4 t≤ 10 t≤ 20 t≤ 36 t≤ 60 t
18 m59 ft≤ 6 t≤ 16 t≤ 28 t≤ 50 t≤ 85 t
20 m66 ft≤ 11 t≤ 20 t≤ 40 t≤ 75 t≤ 120 t≤ 175 t
22 m72 ft≤ 7 t≤ 13 t≤ 33 t≤ 65 t≤ 110 t≤ 160 t
24 m79 ft≤ 8 t≤ 25 t≤ 55 t≤ 100 t≤ 145 t
26 m85 ft≤ 18 t≤ 45 t≤ 85 t≤ 130 t
28 m92 ft≤ 35 t≤ 70 t≤ 115 t
30 m98 ftUse EN*Use EN*
AnchorWeight4 kg6 kg9 kg12 kg15 kg20 kg25 kg33 kg40 kg50 kg60 kg80 kg100 kg
9 lb13 lb20 lb27 lb33 lb44 lb55 lb73 lb88 lb110 lb132 lb176 lb220 lb
SuggestedG40 chain6mm6mm7mm8mm8mm9mm10mm10mm11mm12mm14mm16mm16mm
1/4″1/4″1/4″5/16″5/16″5/16″3/8″3/8″7/16″7/16″1/2″5/8″5/8″
469121520253340506080100
VesselLength
4 m13 ft≤ 2.2 tn
5 m16 ft≤ 1.1 tn≤ 5.5 tn
6 m20 ft≤ ½ tn≤ 3.9 tn≤ 8.8 tn
7 m23 ft≤ ½ tn≤ 2.2 tn≤ 7.7 tn≤ 11.0 tn
8 m26 ft≤ 1.1 tn≤ 6.6 tn≤ 9.4 tn≤ 14.3 tn
9 m30 ft≤ ½ tn≤ 5.5 tn≤ 8.3 tn≤ 12.1 tn≤ 19.8 tn
10 m33 ft≤ 4.4 tn≤ 7.2 tn≤ 10.5 tn≤ 17.6 tn≤ 27.6 tn
11 m36 ft≤ 3.3 tn≤ 6.1 tn≤ 8.8 tn≤ 15.4 tn≤ 25.4 tn
12 m39 ft≤ 5.0 tn≤ 7.2 tn≤ 12.1 tn≤ 23.1 tn≤ 37.5 tn
14 m46 ft≤ 5.0 tn≤ 7.7 tn≤ 16.5 tn≤ 28.7 tn≤ 49.6 tn
16 m52 ft≤ 4.4 tn≤ 11.0 tn≤ 22.0 tn≤ 39.7 tn≤ 66.1 tn
18 m59 ft≤ 6.6 tn≤ 17.6 tn≤ 30.9 tn≤ 55.1 tn≤ 93.7 tn
20 m66 ft≤ 12.1 tn≤ 22.0 tn≤ 44.1 tn≤ 82.7 tn≤ 132.3 tn≤ 192.9 tn
22 m72 ft≤ 7.7 tn≤ 14.3 tn≤ 36.4 tn≤ 71.7 tn≤ 121.3 tn≤ 176.4 tn
24 m79 ft≤ 8.8 tn≤ 27.6 tn≤ 60.6 tn≤ 110.2 tn≤ 159.8 tn
26 m85 ft≤ 19.8 tn≤ 49.6 tn≤ 93.7 tn≤ 143.3 tn
28 m92 ft≤ 38.6 tn≤ 77.2 tn≤ 126.8 tn
30 m98 ftUse EN*Use EN*
Anchorweight4 kg6 kg9 kg12 kg15 kg20 kg25 kg33 kg40 kg50 kg60 kg80 kg100 kg
9 lb13 lb20 lb27 lb33 lb44 lb55 lb73 lb88 lb110 lb132 lb176 lb220 lb
Suggestedchain G406 mm6 mm7 mm8 mm8 mm9 mm10 mm10 mm11 mm12 mm14 mm16 mm16 mm
1/4″1/4″1/4″5/16″5/16″5/16″3/8″3/8″7/16″7/16″1/2″5/8″5/8″
469121520253340506080100
VesselLength
4 m13 ft≤ 4400 lb
5 m16 ft≤ 2200 lb≤ 11000 lb
6 m20 ft≤ 1100 lb≤ 7700 lb≤ 17600 lb
7 m23 ft≤ 1100 lb≤ 4400 lb≤ 15400 lb≤ 22000 lb
8 m26 ft≤ 2200 lb≤ 13200 lb≤ 18700 lb≤ 28700 lb
9 m30 ft≤ 1100 lb≤ 11000 lb≤ 16500 lb≤ 24300 lb≤ 39700 lb
10 m33 ft≤ 8800 lb≤ 14300 lb≤ 20900 lb≤ 35300 lb≤ 55100 lb
11 m36 ft≤ 6600 lb≤ 12100 lb≤ 17600 lb≤ 30900 lb≤ 50700 lb
12 m39 ft≤ 9900 lb≤ 14300 lb≤ 24300 lb≤ 46300 lb≤ 75000 lb
14 m46 ft≤ 9900 lb≤ 15400 lb≤ 33100 lb≤ 57300 lb≤ 99200 lb
16 m52 ft≤ 8800 lb≤ 22000 lb≤ 44100 lb≤ 79400 lb≤ 132300 lb
18 m59 ft≤ 13200 lb≤ 35300 lb≤ 61700 lb≤ 110200 lb≤ 187400 lb
20 m66 ft≤ 24300 lb≤ 44100 lb≤ 88200 lb≤ 165300 lb≤ 264600 lb≤ 385800 lb
22 m72 ft≤ 15400 lb≤ 28700 lb≤ 72800 lb≤ 143300 lb≤ 242500 lb≤ 352700 lb
24 m79 ft≤ 17600 lb≤ 55100 lb≤ 121300 lb≤ 220500 lb≤ 319700 lb
26 m85 ft≤ 39700 lb≤ 99200 lb≤ 187400 lb≤ 286600 lb
28 m92 ft≤ 77200 lb≤ 154300 lb≤ 253500 lb
30 m98 ftUse EN*Use EN*
Anchorweight4 kg6 kg9 kg12 kg15 kg20 kg25 kg33 kg40 kg50 kg60 kg80 kg100 kg
9 lb13 lb20 lb27 lb33 lb44 lb55 lb73 lb88 lb110 lb132 lb176 lb220 lb
SuggestedG40 chain6 mm6 mm7 mm8 mm8 mm9 mm10 mm10 mm11 mm12 mm14 mm16 mm16 mm
1/4″1/4″1/4″5/16″5/16″5/16″3/8″3/8″7/16″7/16″1/2″5/8″5/8″

LARGER ROCNA ANCHORS

Our charts do not accommodate vessels requiring anchors larger than the Rocna Original 110 (243 lb) or Rocna Mk II 100 (220 lb). This is because of increasing complexities of the factors involved. Please enquire about larger Rocna anchor sizes.

Classification society rules and/or legal requirements may mandate anchor sizes for these vessels.

CLASSIFICATION RULES SIZING FOR LARGER ANCHORS

Rocna anchors may be sized by classification society rules for SHHP anchors. An SHHP type is usually permitted a mass 33% lighter than HHP types, or 50% lighter than “standard stockless” types. Classified sizing is based on a vessel’s type, purpose, and calculated Equipment Number (E.N.).

For more information, please consult the Rocna Knowledge Base articles on our sizing recommendations and classification and certification.

Our Anchor Sizing is Conservative

Unlike other manufacturers, our anchor sizing recommendations are intended to provide an anchor adequate for use in most all conditions. We base our calculations on 50 knots of wind, associated surge, and poor holding bottoms. For more on our philosophy and rationale, please consult our Knowledge Base article on our sizing recommendations.

This chart is a guideline only, so if you’d like further information please enquire with us for further advice.

The Rocna 150 (331 lb) and Larger

We do not provide standard recommendations for boats larger than those for which the Rocna 110 (243 lb) would be the recommended size. This is because of increasing complexities of the factors involved.

Furthermore, classification society rules and/or legal requirements are likely to dictate the anchor sizes mandated for these vessels.

Rocna and Vulcan Anchor Bow Compatibility

To confirm that which Rocna or Vulcan anchor will fit your vessel, there are a number of resources below to assist you.

Rocna Anchors Dimensions

Measurements important to the fitting of the anchor on a bow roller are reproduced on this sheet. Using these drawings and a tape measure, many boaters can easily determine that a Rocna or Vulcan will fit their boat.

Visit our Rocna Anchors Dimensions Page or Download as PDF here:

Rocna Knowledge Base

The Rocna Knowledge Base features a large and ever-growing collection of “boat fit cases”, with photos and other information, under Rocna bow compatibility. Popular production boats are covered, and examples of other owners of your boat type successfully fitting a Rocna or Vulcan will allow you to invest with confidence.

Also included are articles and recommendations on the topic of custom bow roller assembly design.

Which Will Fit Best, Rocna or Vulcan?

Rocna anchors are intended to fit well on most vessels. The Rocna Mk II offers improved clearance vs the Rocna Original at the shank-end and the roll-bar. The Vulcan is specifically designed to fit a wider range of vessels with the omission of a roll-bar to clear anchor platforms, bowsprits, or prods.

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