Fish weight calculator
Estimate weight from length, or length and girth, using species-specific equations. Release the fish, keep the number.
Standard weight at length
| Length | Standard weight |
|---|---|
| 16 in | 1.54 lb |
| 18 in | 2.24 lb |
| 20 in | 3.13 lb |
| 22 in | 4.23 lb |
| 24 in | 5.58 lb |
| 26 in | 7.2 lb |
| 28 in | 9.11 lb |
| 30 in | 11.35 lb |
| 32 in | 13.93 lb |
How this tool works
Length only: standard-weight (Ws) equations from the fisheries literature, log₁₀W = a + b·log₁₀L (W in grams, total length L in mm): largemouth bass (Henson 1991), smallmouth bass (Kolander et al. 1993), walleye (Murphy et al. 1990), northern pike (Willis 1989), rainbow trout (Simpkins and Hubert 1996), black crappie (Neumann and Murphy 1991), bluegill (Hillman 1982) and channel catfish (Brown et al. 1995). Length + girth: the angler's formula W (lb) = L × G² ÷ 800. Standard weight describes an average fish; yours may be heavier or lighter.
FAQ
How accurate is a fish weight calculator?
Usually within 10 to 15% for an average fish. Adding girth improves accuracy for unusually fat or thin fish.
What is relative weight (Wr)?
Actual weight ÷ standard weight × 100. Around 100 is normal; above 105 is a well-fed fish; below 90 is thin.