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


		4	6	9	10	12	15	20	25	33	40	55	70	110
Vessel	Length			Vulcan only	Rocna Orig. only	Vulcan only							Rocna Orig. only	Rocna Orig. only
4 m	13 ft	≤ 2 t
5 m	16 ft	≤ 1 t	≤ 5 t
6 m	20 ft	≤ ½ t	≤ 3.5t	≤ 7 t
7 m	23 ft	≤ ½ t	≤ 2 t	≤ 6 t	≤ 7 t	≤ 9 t
8 m	26 ft		≤ 1 t	≤ 5 t	≤ 6 t	≤ 8 t	≤ 12 t
9 m	30 ft		≤ ½ t	≤ 4 t	≤ 5 t	≤ 7 t	≤ 10 t	≤ 16 t
10 m	33 ft			≤ 3 t	≤ 4 t	≤ 6 t	≤ 8.5 t	≤ 14 t	≤ 22 t
11 m	36 ft			≤ 2 t	≤ 3 t	≤ 5 t	≤ 7 t	≤ 12 t	≤ 20 t
12 m	39 ft					≤ 4 t	≤ 6 t	≤ 10 t	≤ 18 t	≤ 30 t
14 m	46 ft						≤ 4 t	≤ 6 t	≤ 13 t	≤ 23 t	≤ 40 t
16 m	52 ft							≤ 3 t	≤ 9 t	≤ 18 t	≤ 32 t	≤ 60 t
18 m	59 ft								≤ 5 t	≤ 14 t	≤ 25 t	≤ 50 t	≤ 85 t
20 m	66 ft									≤ 10 t	≤ 18 t	≤ 40 t	≤ 75 t	≤ 165 t
22 m	72 ft									≤ 6 t	≤ 12 t	≤ 33 t	≤ 65 t	≤ 150 t
24 m	79 ft										≤ 7 t	≤ 25 t	≤ 55 t	≤ 135 t
26 m	85 ft											≤ 18 t	≤ 45 t	≤ 120 t
28 m	92 ft												≤ 35 t	≤ 105 t
30 m	98 ft													Use EN*
Anchor	Weight	4 kg	6 kg	9 kg	10 kg	12 kg	15 kg	20 kg	25 kg	33 kg	40 kg	55 kg	70 kg	110 kg
		9 lb	13 lb	20 lb	22 lb	27 lb	33 lb	44 lb	55 lb	73 lb	88 lb	121 lb	154 lb	243 lb
Suggested	G40 chain	6mm	6mm	7mm	7mm	8mm	8mm	9mm	10mm	10mm	11mm	12mm	14mm	16mm
		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″


		4	6	9	10	12	15	20	25	33	40	55	70	110
Vessel	Length			Vulcan only	Rocna Orig. only	Vulcan only							Rocna Orig. only	Rocna Orig. only
4 m	13 ft	≤ 2.2 tn
5 m	16 ft	≤ 1.1 tn	≤ 5.5 tn
6 m	20 ft	≤ ½ tn	≤ 3.9 tn	≤ 7.7 tn
7 m	23 ft	≤ ½ tn	≤ 2.2 tn	≤ 6.6 tn	≤ 7.7 tn	≤ 9.9 tn
8 m	26 ft		≤ 1.1 tn	≤ 5.5 tn	≤ 6.6 tn	≤ 8.8 tn	≤ 13.2 tn
9 m	30 ft		≤ ½ tn	≤ 4.4 tn	≤ 5.5 tn	≤ 7.7 tn	≤ 11.0 tn	≤ 17.6 tn
10 m	33 ft			≤ 3.3 tn	≤ 4.4 tn	≤ 6.6 tn	≤ 9.4 tn	≤ 15.4 tn	≤ 24.3 tn
11 m	36 ft			≤ 2.2 tn	≤ 3.3 tn	≤ 5.5 tn	≤ 7.7 tn	≤ 13.2 tn	≤ 22.0 tn
12 m	39 ft					≤ 4.4 tn	≤ 6.6 tn	≤ 11.0 tn	≤ 19.8 tn	≤ 33.1 tn
14 m	46 ft						≤ 4.4 tn	≤ 6.6 tn	≤ 14.3 tn	≤ 25.4 tn	≤ 44.1 tn
16 m	52 ft							≤ 3.3 tn	≤ 9.9 tn	≤ 19.8 tn	≤ 35.3 tn	≤ 66.1 tn
18 m	59 ft								≤ 5.5 tn	≤ 15.4 tn	≤ 27.6 tn	≤ 55.1 tn	≤ 93.7 tn
20 m	66 ft									≤ 11.0 tn	≤ 19.8 tn	≤ 44.1 tn	≤ 82.7 tn	≤ 182 tn
22 m	72 ft									≤ 6.6 tn	≤ 13.2 tn	≤ 36.4 tn	≤ 71.7 tn	≤ 165 tn
24 m	79 ft										≤ 7.7 tn	≤ 27.6 tn	≤ 60.6 tn	≤ 149 tn
26 m	85 ft											≤ 19.8 tn	≤ 49.6 tn	≤ 132 tn
28 m	92 ft												≤ 38.6 tn	≤ 116 tn
30 m	98 ft													Use EN*
Anchor	weight	4 kg	6 kg	9 kg	10 kg	12 kg	15 kg	20 kg	25 kg	33 kg	40 kg	55 kg	70 kg	110 kg
		9 lb	13 lb	20 lb	22 lb	27 lb	33 lb	44 lb	55 lb	73 lb	88 lb	121 lb	154 lb	243 lb
Suggested	G40 chain	6 mm	6 mm	7 mm	7 mm	8 mm	8 mm	9 mm	10 mm	10 mm	11 mm	12 mm	14 mm	16 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


		4	6	9	10	12	15	20	25	33	40	55	70	110
Vessel	Length			Vulcan only	Rocna Orig. only	Vulcan only							Rocna Orig. only	Rocna Orig. only
4 m	13 ft	≤ 4400 lb
5 m	16 ft	≤ 2200 lb	≤ 11000 lb
6 m	20 ft	≤ 1100 lb	≤ 7700 lb	≤ 15400 lb
7 m	23 ft	≤ 1100 lb	≤ 4400 lb	≤ 13200 lb	≤ 15400 lb	≤ 19800 lb
8 m	26 ft		≤ 2200 lb	≤ 11000 lb	≤ 13200 lb	≤ 17600 lb	≤ 26500 lb
9 m	30 ft		≤ 1100 lb	≤ 8800 lb	≤ 11000 lb	≤ 15400 lb	≤ 22000 lb	≤ 35300 lb
10 m	33 ft			≤ 6600 lb	≤ 8800 lb	≤ 13200 lb	≤ 18700 lb	≤ 30900 lb	≤ 48500 lb
11 m	36 ft			≤ 4400 lb	≤ 6600 lb	≤ 11000 lb	≤ 15400 lb	≤ 26500 lb	≤ 44100 lb
12 m	39 ft					≤ 8800 lb	≤ 13200 lb	≤ 22000 lb	≤ 39700 lb	≤ 66100 lb
14 m	46 ft						≤ 8800 lb	≤ 13200 lb	≤ 28700 lb	≤ 50700 lb	≤ 88200 lb
16 m	52 ft							≤ 6600 lb	≤ 19800 lb	≤ 39700 lb	≤ 70500 lb	≤ 132300 lb
18 m	59 ft								≤ 11000 lb	≤ 30900 lb	≤ 55100 lb	≤ 110200 lb	≤ 187400 lb
20 m	66 ft									≤ 22000 lb	≤ 39700 lb	≤ 88200 lb	≤ 165300 lb	≤ 363800 lb
22 m	72 ft									≤ 13200 lb	≤ 26500 lb	≤ 72800 lb	≤ 143300 lb	≤ 330700 lb
24 m	79 ft										≤ 15400 lb	≤ 55100 lb	≤ 121300 lb	≤ 297600 lb
26 m	85 ft											≤ 39700 lb	≤ 99200 lb	≤ 264600 lb
28 m	92 ft												≤ 77200 lb	≤ 231500 lb
30 m	98 ft													Use EN*
Anchor	weight	4 kg	6 kg	9 kg	10 kg	12 kg	15 kg	20 kg	25 kg	33 kg	40 kg	55 kg	70 kg	110 kg
		9 lb	13 lb	20 lb	22 lb	27 lb	33 lb	44 lb	55 lb	73 lb	88 lb	121 lb	154 lb	243 lb
Suggested	G40 chain	6 mm	6 mm	7 mm	7 mm	8 mm	8 mm	9 mm	10 mm	10 mm	11 mm	12 mm	14 mm	16 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


		4	6	9	12	15	20	25	33	40	50	60	80	100
Vessel	Length
4 m	13 ft	≤ 2 t
5 m	16 ft	≤ 1 t	≤ 5 t
6 m	20 ft	≤ ½ t	≤ 3.5 t	≤ 8 t
7 m	23 ft	≤ ½ t	≤ 2 t	≤ 7 t	≤ 10 t
8 m	26 ft		≤ 1 t	≤ 6 t	≤ 8.5 t	≤ 13 t
9 m	30 ft		≤ ½ t	≤ 5 t	≤ 7.5 t	≤ 11 t	≤ 18 t
10 m	33 ft			≤ 4 t	≤ 6.5 t	≤ 9.5 t	≤ 16 t	≤ 25 t
11 m	36 ft			≤ 3 t	≤ 5.5 t	≤ 8 t	≤ 14 t	≤ 23 t
12 m	39 ft				≤ 4.5 t	≤ 6.5 t	≤ 11 t	≤ 21 t	≤ 34 t
14 m	46 ft					≤ 4.5 t	≤ 7 t	≤ 15 t	≤ 26 t	≤ 45 t
16 m	52 ft						≤ 4 t	≤ 10 t	≤ 20 t	≤ 36 t	≤ 60 t
18 m	59 ft							≤ 6 t	≤ 16 t	≤ 28 t	≤ 50 t	≤ 85 t
20 m	66 ft								≤ 11 t	≤ 20 t	≤ 40 t	≤ 75 t	≤ 120 t	≤ 175 t
22 m	72 ft								≤ 7 t	≤ 13 t	≤ 33 t	≤ 65 t	≤ 110 t	≤ 160 t
24 m	79 ft									≤ 8 t	≤ 25 t	≤ 55 t	≤ 100 t	≤ 145 t
26 m	85 ft										≤ 18 t	≤ 45 t	≤ 85 t	≤ 130 t
28 m	92 ft											≤ 35 t	≤ 70 t	≤ 115 t
30 m	98 ft												Use EN*	Use EN*
Anchor	Weight	4 kg	6 kg	9 kg	12 kg	15 kg	20 kg	25 kg	33 kg	40 kg	50 kg	60 kg	80 kg	100 kg
		9 lb	13 lb	20 lb	27 lb	33 lb	44 lb	55 lb	73 lb	88 lb	110 lb	132 lb	176 lb	220 lb
Suggested	G40 chain	6mm	6mm	7mm	8mm	8mm	9mm	10mm	10mm	11mm	12mm	14mm	16mm	16mm
		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″


		4	6	9	12	15	20	25	33	40	50	60	80	100
Vessel	Length
4 m	13 ft	≤ 2.2 tn
5 m	16 ft	≤ 1.1 tn	≤ 5.5 tn
6 m	20 ft	≤ ½ tn	≤ 3.9 tn	≤ 8.8 tn
7 m	23 ft	≤ ½ tn	≤ 2.2 tn	≤ 7.7 tn	≤ 11.0 tn
8 m	26 ft		≤ 1.1 tn	≤ 6.6 tn	≤ 9.4 tn	≤ 14.3 tn
9 m	30 ft		≤ ½ tn	≤ 5.5 tn	≤ 8.3 tn	≤ 12.1 tn	≤ 19.8 tn
10 m	33 ft			≤ 4.4 tn	≤ 7.2 tn	≤ 10.5 tn	≤ 17.6 tn	≤ 27.6 tn
11 m	36 ft			≤ 3.3 tn	≤ 6.1 tn	≤ 8.8 tn	≤ 15.4 tn	≤ 25.4 tn
12 m	39 ft				≤ 5.0 tn	≤ 7.2 tn	≤ 12.1 tn	≤ 23.1 tn	≤ 37.5 tn
14 m	46 ft					≤ 5.0 tn	≤ 7.7 tn	≤ 16.5 tn	≤ 28.7 tn	≤ 49.6 tn
16 m	52 ft						≤ 4.4 tn	≤ 11.0 tn	≤ 22.0 tn	≤ 39.7 tn	≤ 66.1 tn
18 m	59 ft							≤ 6.6 tn	≤ 17.6 tn	≤ 30.9 tn	≤ 55.1 tn	≤ 93.7 tn
20 m	66 ft								≤ 12.1 tn	≤ 22.0 tn	≤ 44.1 tn	≤ 82.7 tn	≤ 132.3 tn	≤ 192.9 tn
22 m	72 ft								≤ 7.7 tn	≤ 14.3 tn	≤ 36.4 tn	≤ 71.7 tn	≤ 121.3 tn	≤ 176.4 tn
24 m	79 ft									≤ 8.8 tn	≤ 27.6 tn	≤ 60.6 tn	≤ 110.2 tn	≤ 159.8 tn
26 m	85 ft										≤ 19.8 tn	≤ 49.6 tn	≤ 93.7 tn	≤ 143.3 tn
28 m	92 ft											≤ 38.6 tn	≤ 77.2 tn	≤ 126.8 tn
30 m	98 ft												Use EN*	Use EN*
Anchor	weight	4 kg	6 kg	9 kg	12 kg	15 kg	20 kg	25 kg	33 kg	40 kg	50 kg	60 kg	80 kg	100 kg
		9 lb	13 lb	20 lb	27 lb	33 lb	44 lb	55 lb	73 lb	88 lb	110 lb	132 lb	176 lb	220 lb
Suggested	chain G40	6 mm	6 mm	7 mm	8 mm	8 mm	9 mm	10 mm	10 mm	11 mm	12 mm	14 mm	16 mm	16 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″


		4	6	9	12	15	20	25	33	40	50	60	80	100
Vessel	Length
4 m	13 ft	≤ 4400 lb
5 m	16 ft	≤ 2200 lb	≤ 11000 lb
6 m	20 ft	≤ 1100 lb	≤ 7700 lb	≤ 17600 lb
7 m	23 ft	≤ 1100 lb	≤ 4400 lb	≤ 15400 lb	≤ 22000 lb
8 m	26 ft		≤ 2200 lb	≤ 13200 lb	≤ 18700 lb	≤ 28700 lb
9 m	30 ft		≤ 1100 lb	≤ 11000 lb	≤ 16500 lb	≤ 24300 lb	≤ 39700 lb
10 m	33 ft			≤ 8800 lb	≤ 14300 lb	≤ 20900 lb	≤ 35300 lb	≤ 55100 lb
11 m	36 ft			≤ 6600 lb	≤ 12100 lb	≤ 17600 lb	≤ 30900 lb	≤ 50700 lb
12 m	39 ft				≤ 9900 lb	≤ 14300 lb	≤ 24300 lb	≤ 46300 lb	≤ 75000 lb
14 m	46 ft					≤ 9900 lb	≤ 15400 lb	≤ 33100 lb	≤ 57300 lb	≤ 99200 lb
16 m	52 ft						≤ 8800 lb	≤ 22000 lb	≤ 44100 lb	≤ 79400 lb	≤ 132300 lb
18 m	59 ft							≤ 13200 lb	≤ 35300 lb	≤ 61700 lb	≤ 110200 lb	≤ 187400 lb
20 m	66 ft								≤ 24300 lb	≤ 44100 lb	≤ 88200 lb	≤ 165300 lb	≤ 264600 lb	≤ 385800 lb
22 m	72 ft								≤ 15400 lb	≤ 28700 lb	≤ 72800 lb	≤ 143300 lb	≤ 242500 lb	≤ 352700 lb
24 m	79 ft									≤ 17600 lb	≤ 55100 lb	≤ 121300 lb	≤ 220500 lb	≤ 319700 lb
26 m	85 ft										≤ 39700 lb	≤ 99200 lb	≤ 187400 lb	≤ 286600 lb
28 m	92 ft											≤ 77200 lb	≤ 154300 lb	≤ 253500 lb
30 m	98 ft												Use EN*	Use EN*
Anchor	weight	4 kg	6 kg	9 kg	12 kg	15 kg	20 kg	25 kg	33 kg	40 kg	50 kg	60 kg	80 kg	100 kg
		9 lb	13 lb	20 lb	27 lb	33 lb	44 lb	55 lb	73 lb	88 lb	110 lb	132 lb	176 lb	220 lb
Suggested	G40 chain	6 mm	6 mm	7 mm	8 mm	8 mm	9 mm	10 mm	10 mm	11 mm	12 mm	14 mm	16 mm	16 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:

2023 Rocna Anchors Sizing

1 file(s) 103.97 KB

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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.