Minnesota's DNR published a chart in our fishing regulations which lays out some formulas you can use to weigh a fish without a scale, but you will need a tape measure and paper and pencil, or a calculator.
The basic measurement is to measure the fish you've caught, and on some species, measure the girth - the distance around the body at its widest point (don't spread the dorsal fin, that is cheating). All measurements should be in inches.
Then plug your numbers in to the appropriate formula as laid out below.
Book Example:
An 18" walleye weighs about 2.16 pounds (5832 [18 * 18 * 18] /
2700 = 2.16).
Real life examples: I am basing these numbers about what I know - the rough sizes of the fish, as compared to measurements I know about myself - for example - when spread apart, the distance from the tip of my thumb to the tip of my middle index finger is 8", etc.
Sooooo, just to play devils advocate, I am estimating the length of the LM Bass I caught in 1998 to be approximately 24", and the girth to be about 10".
Using the formula: 24 * 24 * 10 = 5760 / 1200 = 4.8 pounds.
For the Sunfish I caught in 1991, I am estimating the length at 9", so in our formula, it becomes: 9 * 9 * 9 = 729 / 1200 = .6075 pounds. A 8" sunfish would have weighed about .42 pounds, and a 8.5" fish would have weighed about .51 pounds.
Please remember, these weights are based on "guestimates" of the fish'es body size, not on lengths I measured with a tape. I didn't have a tape with me when I caught these fish.
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Copyright 2000© Jim Laumann.
