Lakers are the giants of cold, deep water, and their length tells you a lot about their weight. This lake trout length-to-weight chart estimates weight from length for a fish in average condition, so you can size up a laker before a quick release.
Lake trout length-to-weight chart
| Length | Average weight |
|---|---|
| 18″ | 2.16 lb |
| 20″ | 2.96 lb |
| 22″ | 3.94 lb |
| 24″ | 5.12 lb |
| 26″ | 6.51 lb |
| 28″ | 8.13 lb |
| 30″ | 10.0 lb |
| 32″ | 12.1 lb |
| 34″ | 14.6 lb |
| 36″ | 17.3 lb |
| 38″ | 20.3 lb |
| 40″ | 23.7 lb |
These figures use weight (lb) = length³ ÷ 2,700 (length in inches), set to average-condition fish. Big lakers from rich, forage-heavy waters run heavier — and the largest fish get proportionally stouter than the chart shows.
What’s an average lake trout — and what’s a trophy?
Lake trout size varies enormously by water. In smaller inland and stocked lakes, a typical catch is 18–26 inches and 2–6 pounds; in big Canadian lakes and the Great Lakes, the average runs much larger. Anglers widely treat 20 pounds, or 30+ inches, as a trophy laker (a convention, not an official mark). The IGFA all-tackle rod-and-reel record is 72 pounds, from Great Bear Lake, Northwest Territories, in 1995 — and even larger lake trout have turned up in commercial nets.
Put a number on your exact fish (worked example)
Weight (lb) = Length × Girth² ÷ 800
A 30-inch laker with an 18-inch girth works out to 30 × 18 × 18 ÷ 800 = 12.1 lb, above the 10.0 lb length-only average — a well-fed fish. Measure both and use our free fish weight calculator; see how to estimate a fish’s weight.
Why two lakers of the same length weigh differently
Lake trout grow slowly and stay lean where forage is limited, and get deep and heavy where ciscoes, whitefish, and smelt are abundant. Fall pre-spawn females carry extra weight, and the biggest fish get proportionally heavier per inch — which is why a chart is a starting point.
Where and when to find bigger lake trout
Lakers live in large, deep, cold, well-oxygenated lakes and are locked to cold water — roughly 40–55°F. In summer they drop below the thermocline into deep, cold strata, so anglers reach them with downriggers, lead-core line, or vertical jigging over deep rock structure, humps, and drop-offs. Right after ice-out and again in late fall, the same fish move shallow and can be caught on casting gear.
Lake trout weight FAQ
How much does a 30-inch lake trout weigh? About 10 pounds in average condition; a heavy fish can top 12.
What’s a trophy lake trout? Roughly 20 pounds or 30+ inches.
Where are lake trout in summer? Deep, below the thermocline — you’ll need downriggers, lead core, or vertical jigging to reach them.
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