Fly Fishing

Condition Factor Calculators – Fulton’s K Factor & ‘Traditional’ CF

Condition Factor is a good measurement that allows anglers a reliable way of comparing the condition of fish of different sizes. While most NZ anglers measure their catch in weight, condition factor allows us a better understanding of a particular fishes condition. Regardless of what CF system you are using, the higher the condition factor the better. 

"Traditional" Condition Factor Calculator

The above condition factor calculator is the method and formula I’ve seen used most often and is based on an imperial measurement system. However, this calculation is rarely used anywhere outside of the angling community, possibly due to the fact that it is an imperial measurement system. 

The formula is as follows:

CF = weight (lbs) / length^3 (inches) * 100,000

Fulton's Condition Factor Calculator (K Factor)

Fulton’s ‘K Factor’ measurement gained popularity in the early 1900s and is commonly used in scientific literature. One attractive thing about this system is that it is based around the number ‘1. A number of 1 suggests a fish of average condition, below one is below average and above one is above average. Another attractive thing about this system is it’s based on metric measurements, and as we all know the metric system is infinitely superior to the imperial measurement system (US readers please leave complaints in the comments section).

The formula:

K Factor = weight (grams) / length ^ 3 (cm) * 100

What's the difference?

In fairness to both they are very similar measurements, they just have two key differences…

  •  The measurement system used
  • The multiplier which only purpose is to give us a easily readable number rather than something like 0.0012344

Either way both measurements allow anglers to compare fish of different weights and lengths. I personally know I’d rather be catching a well conditioned 5lb trout than a skinny ‘hasn’t eaten all year’ 6lb trout. Also I prefer the K factor system when comparing the two, but that’s just me…

What do you prefer?

Comment below.

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