How much does a rainbow trout weigh?
Upload a photo of your catch, or use the tools below, to estimate its weight.
About the rainbow trout
Typical adult length: 8–20 in (about 0.3–5.3 lb)
- Lifespan
- Typically lives 4 to 6 years in the wild, longer in some lake populations.
- Habitat
- Lives in cold, clean streams, rivers, and lakes with good oxygen levels.
- Diet
- Feeds on aquatic insects, small fish, and crustaceans.
- Baits & techniques
- Small spinners, flies, and PowerBait-style baits fished in current or near structure work well.
- Best season
- Spring and fall, when water temperatures are cooler, tend to be most productive.
- Best time of day
- Early morning and evening are often best, especially during insect hatches.
- Steelhead are simply rainbow trout that migrate to the ocean or large lakes before returning to rivers to spawn.
- Rainbow trout are native to the Pacific coast of North America but have been widely stocked worldwide.
- They're known for acrobatic jumps when hooked, making them popular with fly anglers.
Rainbow Trout length-to-weight chart
10 inches up to record size (45 in), using the standard length-to-weight formula for this species.
| Length (in) | Estimated weight (lb) |
|---|---|
| 10 | 0.7 |
| 12 | 1.2 |
| 14 | 1.8 |
| 16 | 2.7 |
| 18 | 3.9 |
| 20 | 5.3 |
| 22 | 7.1 |
| 24 | 9.2 |
| 26 | 11.7 |
| 28 | 14.6 |
| 30 | 18.0 |
| 32 | 21.8 |
| 34 | 26.2 |
| 36 | 31.1 |
| 38 | 36.6 |
| 40 | 42.7 |
| 42 | 49.4 |
| 44 | 56.8 |
| 45 | 60.8 |
Estimating weight without a scale
Length-to-weight formulas like the one above assume a typical rainbow 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.