Improved Fish Weight Formula - Figure out weight with length and girth

The generally accepted formula for figuring out a fishes weight based on length and girth is:

Weight = (Length X Girth²)/800

I recently saw data that showed a better formula is:

Weight = (Length X Girth²)/690

So, for the mathematically challenged (like my wife), here is how it works:

Lets say our fish is a 15" long rainbow that is 11" around at the widest point (girth).

Weight = (15 X 11²)/690
Do the girth squared first... 11² is: 11 X 11 = 121 and plug it in
Weight = (15 X 121)/690
Now finish the length times width... 15 X 121 =  1815
One last bit of math: Weight = 1815/690
The final weight (estimate) is: 2.6 pounds 

I have personally only verified this with 3 fish, but it worked much better than the original. 

Fish Weight Formula - Length to Weight Calculation 

Here is a formula for determining fish weight based on length and girth measurements.

Weight = (Length X Girth²) / 800

Example: A fish that measures 14" in length and 8" around (girth).

1.) Weight = (14 X 8²) / 800
   8² = 8 X 8 = 64
2.) Weight = (14 X 64) / 800
   14 X 64 = 896
3.) Weight = 896 / 800

Result: Weight is approx. 1.1 lbs.

Note: If applying this formula to a long and narrow fish (like a Pike), use 900 instead of 800.