Fish Weight Calculators
Remember that no length/weight formula can ever replace an accurate scale. However, the following calculators should enable to you to get a fair estimate that's within about 10 percent of the actual weight.
Note: Be sure no matter what species of fish and measure from the lower jaw to the fork of the tail and measure the girth at the widest part around the body. Make sure that at no time should your tape measure or other measuring device go under the gill plate or into the gills!