How much does a brown trout weigh?
Upload a photo of your catch, or use the tools below, to estimate its weight.
About the brown trout
Typical adult length: 10–22 in (about 0.6–5.9 lb)
- Lifespan
- Typically lives 8 to 12 years, longer than most other trout species.
- Habitat
- Prefers cool, clean streams and rivers, often holding in deeper pools or undercut banks.
- Diet
- Feeds on aquatic insects, small fish, and crustaceans, becoming more predatory as it grows.
- Baits & techniques
- Streamers, nymphs, and small crankbaits fished naturally through likely holding water are effective.
- Best season
- Fall is notable for the spawning run, while spring and early summer also fish well.
- Best time of day
- Low light periods, dawn and dusk, often produce the biggest, most cautious fish.
- Brown trout are native to Europe and western Asia but were introduced to North America in the late 1800s.
- They're generally more wary and harder to catch than rainbow trout, especially as they grow larger.
- Large brown trout become increasingly predatory, feeding heavily on smaller fish.
Brown Trout length-to-weight chart
10 inches up to record size (44 in), using the standard length-to-weight formula for this species.
| Length (in) | Estimated weight (lb) |
|---|---|
| 10 | 0.6 |
| 12 | 1.0 |
| 14 | 1.5 |
| 16 | 2.3 |
| 18 | 3.2 |
| 20 | 4.4 |
| 22 | 5.9 |
| 24 | 7.7 |
| 26 | 9.8 |
| 28 | 12.2 |
| 30 | 15.0 |
| 32 | 18.2 |
| 34 | 21.8 |
| 36 | 25.9 |
| 38 | 30.5 |
| 40 | 35.6 |
| 42 | 41.2 |
| 44 | 47.3 |
Estimating weight without a scale
Length-to-weight formulas like the one above assume a typical brown 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.