Caught a nice largemouth and want to know what it weighs without a scale? This largemouth bass length-to-weight chart gives the average weight for a fish in typical condition — find the length, read across, and you’ve got a solid estimate for catch-and-release, tournament culling, or just settling a debate at the ramp.
Largemouth bass length-to-weight chart
| Length | Average weight |
|---|---|
| 10″ | 0.49 lb |
| 11″ | 0.66 lb |
| 12″ | 0.9 lb |
| 13″ | 1.15 lb |
| 14″ | 1.47 lb |
| 15″ | 1.83 lb |
| 16″ | 2.25 lb |
| 17″ | 2.73 lb |
| 18″ | 3.28 lb |
| 19″ | 3.89 lb |
| 20″ | 4.59 lb |
| 21″ | 5.36 lb |
| 22″ | 6.22 lb |
| 23″ | 7.17 lb |
| 24″ | 8.21 lb |
These figures follow widely published largemouth bass data (In-Fisherman and state fisheries agencies) for a fish in average condition. They’re length-only averages, so treat them as a starting point rather than an exact reading.
What’s an average bass — and what’s a trophy?
Most largemouth an average angler catches run 12–18 inches and about 1 to 4.5 pounds, with a 16-incher (around 2.25 lb) being a very typical “good” fish. A bass over 5 pounds is a big one in most of the country, and true trophies run 7 to 10+ pounds. Double-digit fish are largely a warm-water and Florida-strain phenomenon — the Florida subspecies simply grows bigger than the northern largemouth. Keep in mind “trophy” isn’t an official standard; it’s a regional convention, so a 5-lb fish that’s a giant up north is merely nice in Florida or Texas.
For perspective, the IGFA all-tackle world record is 22 lb 4 oz, caught by George Perry in Georgia back in 1932 — one of the most famous records in all of fishing. It was tied (not broken) by a 22 lb 5 oz fish from Japan in 2009, which didn’t exceed Perry’s mark by the required margin.
Put a number on your exact fish (worked example)
The chart is a length-only average, but girth — the distance around the fish at its fattest point — is what separates a skinny bass from a tank. The classic length-and-girth formula is:
Weight (lb) = Length × Girth² ÷ 800
Say you land a 19-inch largemouth with a 13-inch girth. The chart says a 19-incher averages 3.89 lb, but run the numbers: 19 × 13 × 13 ÷ 800 = 4.0 lb. That pot-bellied pre-spawn female is carrying a little extra over the length-only average — exactly the kind of fish the girth measurement catches.
Drop your own length and girth into our free fish weight calculator and it does this instantly, usually landing within 5–10% of the scale. New to measuring girth? Our guide on how to estimate a fish’s weight walks through it.
Why two bass of the same length weigh differently
A 19-inch bass in March and a 19-inch bass in August can differ by a pound or more. The biggest factor is the spawn: pre-spawn females in early spring are the heaviest of the year, gorging to build energy and loaded with eggs. Forage matters too — a bass fattened on a rich diet of bluegill and shad carries more weight than one scraping by. Genetics (Florida vs. northern strain) and simple body depth round it out.
Where and when to find bigger largemouth
Largemouth are warm-water, structure-oriented ambush predators. Look for them tight to cover — weed beds, sunken logs, brush, standing timber, docks — in clear, warm, vegetated lakes, ponds, and slow river backwaters, most active when water sits roughly in the 65–85°F range. Adults key on sunfish and crayfish, so areas holding bluegill are prime. The trophy window is pre-spawn, early spring, when the year’s biggest females push shallow to feed.
Largemouth bass weight FAQ
How much does a 20-inch largemouth bass weigh? About 4.6 pounds in average condition, though a deep-bodied or pre-spawn fish can top 5.
What’s considered a trophy largemouth bass? Generally 7+ pounds, though anything over 5 lbs is a big fish in most northern and midwestern waters.
Is length or girth more accurate for weight? Girth. Two bass the same length can vary 20%+ in weight, and only girth captures that. Use the calculator for a fish-specific number.
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