Fish Growth Rate Calculator

Work out fish growth rate instantly with clear inputs, formula shown and shareable results.

About Fish Growth Rate Calculator

Specific growth rate is the exponential growth constant, (ln final weight - ln initial weight) / days x 100, and is the standard way to compare growth between fish of different sizes. Average daily gain is the simple arithmetic rate, and dividing feed used by the gain gives the FCR for the period.

Formulas

Specific growth rate

SGR (%/day) = (ln W_final - ln W_initial) / days x 100

Feed conversion

FCR = feed consumed / weight gain

Worked example

With the default values below, Fish Growth Rate Calculator returns Specific Growth Rate of 1.8310%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Initial Average Weightminimum 0.01 g: 50 g
Final Average Weightminimum 0.01 g: 450 g
Growing Periodminimum 1 days: 120 days
Feed Consumed Per Fishminimum 0 g: 650 g

Results

Specific Growth Rate: 1.8310%
Average Daily Gain: 3.3333
Total Weight Gain: 400.00
Feed Conversion Ratio: 1.625

Step by step

1Values used
2Specific growth rate
3Feed conversion
4Specific Growth Rate= 1.8310
5Average Daily Gain= 3.3333
6Total Weight Gain= 400.00
7Feed Conversion Ratio= 1.625

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation or tax into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why use SGR instead of daily gain?

A 50 g fish gaining 2 g/day is growing far faster in relative terms than a 500 g fish gaining the same. SGR normalises for size so growth can be compared across stages.

What FCR is good?

1.0-1.4 for well-managed tilapia and catfish on pelleted feed, 1.5-2.0 for carp polyculture, and above 2.5 indicates overfeeding, poor water quality or disease.