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!