How much does a brook trout weigh?
Upload a photo of your catch, or use the tools below, to estimate its weight.
About the brook trout
Typical adult length: 8–16 in (about 0.3–2 lb)
- Lifespan
- Typically lives 4 to 6 years.
- Habitat
- Prefers cold, clean, well-oxygenated streams and lakes, often in headwaters.
- Diet
- Feeds on aquatic insects, small crustaceans, and occasionally small fish.
- Baits & techniques
- Small spinners, flies, and worms fished in clear, cold water work well.
- Best season
- Spring through early fall, before water temperatures get too warm.
- Best time of day
- Morning and evening tend to be most productive.
- Brook trout are actually a char, not a true trout, closely related to lake trout.
- They're highly sensitive to water temperature and pollution, making them an indicator of stream health.
- Brook trout are the state fish of several eastern US states.
Brook Trout length-to-weight chart
10 inches up to record size (34 in), using the standard length-to-weight formula for this species.
| Length (in) | Estimated weight (lb) |
|---|---|
| 10 | 0.5 |
| 12 | 0.9 |
| 14 | 1.4 |
| 16 | 2.0 |
| 18 | 2.9 |
| 20 | 4.0 |
| 22 | 5.3 |
| 24 | 6.9 |
| 26 | 8.8 |
| 28 | 11.0 |
| 30 | 13.5 |
| 32 | 16.4 |
| 34 | 19.7 |
Estimating weight without a scale
Length-to-weight formulas like the one above assume a typical brook trout shape for a given length - fisheries biologists call this the cube law. Real fish vary: a well-fed fish ahead of spawning season can weigh noticeably more than a lean fish of the same length, and body shape varies fish to fish.
Adding girth (the distance around the fish at its widest point) meaningfully improves the estimate, because it captures how deep-bodied this particular fish actually is instead of assuming average proportions for the species - use the calculator above and fill in girth if you can measure it.
Either way, treat the result as a solid estimate, not a certified weight - see our terms for why these numbers shouldn't be used for tournaments, regulations, or sales.