There’s a Rocna 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 vessel, follow the chart and instructions below the chart.
1 t (metric tonne) = 1,000 kg
ROCNA OR VULCAN MODEL  
4  6  9  10  12  15  20  25  33  40  55  70  110  
Vessel Length  Vulcan only  Rocna only  Vulcan only  Rocna only  Rocna only  
4 m  ≤ 2 t  
5 m  ≤ 1 t  ≤ 5 t  
6 m  ≤ ½ t  ≤ 3.5 t  ≤ 7 t  
7 m  ≤ ½ t  ≤ 2 t  ≤ 6 t  ≤ 7 t  ≤ 9 t  
8 m  ≤ 1 t  ≤ 5 t  ≤ 6 t  ≤ 8 t  ≤ 12 t  
9 m  ≤ ½ t  ≤ 4 t  ≤ 5 t  ≤ 7 t  ≤ 10 t  ≤ 16 t  
10 m  ≤ 3 t  ≤ 4 t  ≤ 6 t  ≤ 8.5 t  ≤ 14 t  ≤ 22 t  
11 m  ≤ 3 t  ≤ 5 t  ≤ 7 t  ≤ 12 t  ≤ 20 t  
12 m  ≤ 4 t  ≤ 6 t  ≤ 10 t  ≤ 18 t  ≤ 30 t  
14 m  ≤ 4 t  ≤ 6 t  ≤ 13 t  ≤ 23 t  ≤ 40 t  
16 m  ≤ 3 t  ≤ 9 t  ≤ 18 t  ≤ 32 t  ≤ 60 t  
18 m  ≤ 5 t  ≤ 14 t  ≤ 25 t  ≤ 50 t  ≤ 85 t  
20 m  ≤ 10 t  ≤ 18 t  ≤ 40 t  ≤ 75 t  ≤ 165 t  
22 m  ≤ 6 t  ≤ 12 t  ≤ 33 t  ≤ 65 t  ≤ 150 t  
24 m  ≤ 7 t  ≤ 25 t  ≤ 55 t  ≤ 135 t  
26 m  ≤ 18 t  ≤ 45 t  ≤ 120 t  
28 m  ≤ 35 t  ≤ 105 t  
30 m  Use EN*  
35 m  Use EN*  
Anchor weight  4 kg  6 kg  6 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  13 lb  22 lb  27 lb  33 lb  44 lb  55 lb  73 lb  88 lb  121 lb  154 lb  243 lb  
Rocna fluke area  460 cm²  590 cm²    795 cm²    1030 cm²  1140 cm²  1415 cm²  1695 cm²  1945 cm²  2300 cm²  2690 cm²  3330 cm² 
Vulcan fluke area  420 cm²  560 cm²  730 cm²    880 cm²  1020 cm²  1240 cm²  1440 cm²  1730 cm²  1970 cm²  2430 cm²     
Rec. 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" 
1 short ton = 2,000 lb
ROCNA OR VULCAN MODEL  
4  6  9  10  12  15  20  25  33  40  55  70  110  
Vessel Length  Vulcan only  Rocna only  Vulcan only  Rocna only  Rocna only  
13 ft  ≤ 2.2 T  
16 ft  ≤ 1.1 T  ≤ 5.5 T  
20 ft  ≤ 0.55 T  ≤ 3.85 T  ≤ 7.7 T  
23 ft  ≤ 0.55 T  ≤ 2.2 T  ≤ 6.6 T  ≤ 7.7 T  ≤ 9.9 T  
26 ft  ≤ 1.1 T  ≤ 5.5 T  ≤ 6.6 T  ≤ 8.8 T  ≤ 13.2 T  
30 ft  ≤ 0.55 T  ≤ 4.4 T  ≤ 5.5 T  ≤ 7.7 T  ≤ 11 T  ≤ 17.6 T  
33 ft  ≤ 3.3 T  ≤ 4.4 T  ≤ 6.6 T  ≤ 9.4 T  ≤ 15.4 T  ≤ 24.3 T  
36 ft  ≤ 3.3 T  ≤ 5.5 T  ≤ 7.7 T  ≤ 13.2 T  ≤ 22.1 T  
39 ft  ≤ 4.4 T  ≤ 6.6 T  ≤ 11 T  ≤ 19.8 T  ≤ 33.1 T  
46 ft  ≤ 4.4 T  ≤ 6.6 T  ≤ 14.3 T  ≤ 25.4 T  ≤ 44.1 T  
52 ft  ≤ 3.3 T  ≤ 9.9 T  ≤ 19.8 T  ≤ 35.3 T  ≤ 66.1 T  
59 ft  ≤ 5.5 T  ≤ 15.4 T  ≤ 27.6 T  ≤ 55.1 T  ≤ 93.7 T  
66 ft  ≤ 11 T  ≤ 19.8 T  ≤ 44.1 T  ≤ 82.7 T  ≤ 181.9 T  
72 ft  ≤ 6.6 T  ≤ 13.2 T  ≤ 36.4 T  ≤ 71.7 T  ≤ 165.4 T  
79 ft  ≤ 7.7 T  ≤ 27.6 T  ≤ 60.6 T  ≤ 148.8 T  
85 ft  ≤ 19.8 T  ≤ 49.6 T  ≤ 132.3 T  
92 ft  ≤ 38.6 T  ≤ 115.7 T  
98 ft  Use EN*  
115 ft  Use EN*  
Anchor weight  4 kg  6 kg  6 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  13 lb  22 lb  27 lb  33 lb  44 lb  55 lb  73 lb  88 lb  121 lb  154 lb  243 lb  
Rocna fluke area  71 in²  91 in²    123 in²    160 in²  177 in²  219 in²  263 in²  301 in²  357 in²  417 in²  516 in² 
Vulcan fluke area  65 in²  87 in²  113 in²    136 in²  158 in²  192 in²  223 in²  268 in²  305 in²  377 in²     
Rec. G40 chain  6mm  6mm  7mm  7mm  8mm  8mm  9mm  10mm  10mm  11mm  12mm  14mm  16mm 
1/4"  1/4"  1/4"  1/4"  1/4"  5/16"  5/16"  3/8"  3/8"  7/16"  7/16"  1/2"  5/8" 
ROCNA OR VULCAN MODEL  
4  6  9  10  12  15  20  25  33  40  55  70  110  
Vessel Length  Vulcan only  Rocna only  Vulcan only  Rocna only  Rocna only  
13 ft  ≤4,400  
16 ft  ≤2,200  ≤11,020  
20 ft  ≤1,100  ≤7,720  ≤15,430  
23 ft  ≤1,100  ≤4,410  ≤13,230  ≤15,430  ≤19,840  
26 ft  ≤2,210  ≤11,020  ≤13,230  ≤17,640  ≤26,460  
30 ft  ≤1,100  ≤8,820  ≤11,020  ≤15,430  ≤22,050  ≤35,270  
33 ft  ≤6,610  ≤8,820  ≤13,230  ≤18,740  ≤30,860  ≤48,500  
36 ft  ≤6,610  ≤11,020  ≤15,430  ≤26,460  ≤44,090  
39 ft  ≤8,820  ≤13,230  ≤22,050  ≤39,680  ≤66,140  
46 ft  ≤8,820  ≤13,230  ≤28,660  ≤50,710  ≤88,180  
52 ft  ≤6,610  ≤19,840  ≤39,680  ≤70,550  ≤132,300  
59 ft  ≤11,020  ≤30,860  ≤55,120  ≤110,230  ≤187,400  
66 ft  ≤22,050  ≤39,680  ≤88,180  ≤165,300  ≤363,000  
72 ft  ≤13,230  ≤26,460  ≤72,750  ≤143,300  ≤330,000  
79 ft  ≤15,430  ≤55,120  ≤121,300  ≤297,000  
85 ft  ≤39,680  ≤99,200  ≤265,000  
92 ft  ≤77,200  ≤231,000  
98 ft  Use EN*  
115 ft  Use EN*  
Anchor weight  4 kg  6 kg  6 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  13 lb  22 lb  27 lb  33 lb  44 lb  55 lb  73 lb  88 lb  121 lb  154 lb  243 lb  
Rocna fluke area  71 in²  91 in²    123 in²    160 in²  177 in²  219 in²  263 in²  301 in²  357 in²  417 in²  516 in² 
Vulcan fluke area  65 in²  87 in²  113 in²    136 in²  158 in²  192 in²  223 in²  268 in²  305 in²  377 in²     
Rec. 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" 
To choose the correctly sized Rocna or Vulcan anchor, find your vessel’s length from column on the left, then track across that row until you find the first column with a displacement (in tonnes) the same or larger than the displacement of your vessel. The top of the column with the selected displacement indicates the recommended Rocna or Vulcan anchor.
For multihulls: use the chart as instructed, then select the model one size larger.
Our sizing is conservative
Unlike other manufacturers, our 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.
(*) Classification Rules sizing
Rocna anchors from sized 110 kg (243 lb) and above may be sized based on classification society Rules for Ships for SHHP anchors. Modern rules permit a mass 33% lighter than HHP types, or 50% lighter than “standard stockless” types. Anchor sizing is based on a vessel’s separately calculated Equipment Number (EN). For more information, please consult the Rocna Knowledge Base articles on our sizing recommendations and Classification and Certification.
Equipment Number (EN) range (applies to Lloyd's, RINA)  
50–70  70–110  110–130  130–175  > 175  
ROCNA MODEL  110  150  200  275  Please enquire 

Anchor weight  110 kg  150 kg  200 kg  275 kg  
243 lb  331 lb  441 lb  606 lb  
Fluke surface area  2300 cm²  4470 cm²  5560 cm²  6510 cm² 