The following Halibut lenght/weight chart comes from the Pacific Halibut Commission.

Net Weight column is lbs, dressed out, head off, slime and ice deducted

Round Weight is whole fish, as caught

Length (inches) Net wt (lbs) Round wt (lbs)   Length (inches) Net wt (lbs) Round wt (lbs)
20 2.3 3.1 59 77.5 103.1
21 2.7 3.6 60 81.8 108.9
22 3.2 4.2 61 86.5 114.8
23 3.7 4.9 62 91 121.1
24 4.2 5.6   63 95.9 127.5
25 4.8 6.4 64 100.9 134.2
26 5.4 7.2 65 106.1 141.1
27 6.2 8.2 66 111.5 148.2
28 6.9 9.2 67 117 155.6
29 7.8 10.3   68 122.8 163.3
30 8.7 11.5 69 128.7 171.2
31 9.6 12.8 70 134.9 179.4
32 10.7 14.2 71 141.2 187.8
33 11.8 15.7 72 147.7 196.5
34 13 17.3   73 154.5 205.5
35 14.3 19 74 161.5 214.7
36 15.6 20.8 75 168.6 224.3
37 17.1 22.7 76 176 234.1
38 18.6 24.8 77 183.7 244.3
39 20.3 27   78 191.5 254.7
40 22 29.3 79 199.6 265.4
41 23.8 31.7 80 207.9 276.5
42 25.8 34.3 81 216.4 287.8
43 27.8 37 82 225.2 299.5
44 30 39.8   83 234.2 311.5
45 32.2 42.9 84 243.5 323.8
46 34.6 46 85 253 336.5
47 37.1 49.3 86 262.7 349.5
48 39.7 52.8 87 272.8 362.8
49 42.5 56.5   88 283.1 376.5
50 45.3 60.3 89 293.6 390.5
51 48.3 64.3 90 304.4 404.9
52 51.5 68.5 91 315.5 419.7
53 54.8 72.8 92 326.9 434.8
54 58.2 77.4   93 338.6 450.3
55 61.7 82.1 94 350.5 466.2
56 65.4 87 95 362.7 482.4
57 69.3 92.2 96 375.3 499.1
58 73.3 97.5 97 383.2 508.7