Fish Weight Calculator

When you catch a fish and have no scales, you can get very close to the actual weight using this formula.

Fill in the Length and Girth,
then click on "Calculate".

Here is the formula to use if you aren't online .

(Length X  Length) X Girth then divide the answer by 1200.

ie: L 20 X L20 =400 X G 16

This gives an answer of 6400 to divide by 1200 which equals the weight of 5.333 pounds.

The general formula for all fish is:

WEIGHT = (length x girth2) / 800

Where:

length & girth are measured in inches,
Girth is the distance around the body of the fish at its largest point, and all answers are in pounds.
To measure your fish:

A = length and B = girth

This formulas is the generally accepted formula for all fish with a 5% error factor. Below you will see some formulas specific to species. Using these will reduce the error factor for these species. As a general rule, even for marlin and the like, the “trout weight” formula will do just fine.

Formulas
bass weight = (length x length x girth) / 1,200

pike weight = (length x length x length) / 3,500

trout weight = (length x girth x girth) / 800

For example, you catch a 16 inch trout with an 11 inch girth. Using the formula for trout above: (16 x11 x 11) / 800 = 2.42 pounds. Your trout weighs approximately 2.42 pounds.

 Or here is the PDF form you can print out.. This form uses the 800 number since it is for overall species.