What this calculator does
Feed conversion ratio is feed consumed divided by weight gained, so a lower number is better. An FCR of 1.5 means 1.5 kg of feed produced 1 kg of gain. It is the central efficiency measure in livestock and aquaculture, because feed is usually the largest single cost.
Typical values differ enormously by species and reflect biology rather than management quality alone. Farmed fish and broiler chickens commonly run around 1.2 to 1.8, pigs around 2.5 to 3.5, and beef cattle 6 or higher. Comparing an FCR across species says little; comparing it against the same species last cycle says a great deal.
The formula
Weight gain is the final weight less the initial weight. Feed conversion ratio is the total feed consumed divided by that gain. Feed efficiency is the reciprocal expressed as a percentage, so an FCR of 2.0 corresponds to 50% efficiency. Both describe the same thing in opposite directions.
| Term | Meaning |
|---|---|
| FCR | Feed consumed per unit of weight gained. Lower is better. |
| Feed efficiency | Gain per unit of feed, the reciprocal of FCR, expressed as a percentage. |
| Weight gain | Final weight less initial weight, the denominator of the ratio. |
| Feed cost per kg gain | FCR multiplied by feed price, which is the figure that actually matters commercially. |
The inputs explained
| Field | What to enter |
|---|---|
| Total feed consumed (kg) | Total feed consumed over the period, in kilograms. Use as-fed weight consistently, or dry matter consistently, but do not mix the two. |
| Initial weight (kg) | Starting total weight of the group. |
| Final weight (kg) | Finishing total weight of the same group. |
When to use it
Monitoring a production cycle
FCR calculated at the end of each cycle and compared against previous ones is the standard efficiency measure, and a drift upward is an early sign of a problem.
Evaluating a feed change
A cheaper feed that raises FCR may cost more per kilogram of gain than the dearer one it replaced, and only the combination of the two figures answers that.
Costing production
Multiplying FCR by feed price gives feed cost per kilogram of gain, which is the number that goes into a margin calculation.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does feed consumed change the FCR?
The same weight gain achieved on different amounts of feed.
| Feed consumed | Feed conversion ratio | Weight gain | Feed efficiency (gain per unit feed) |
|---|---|---|---|
| 1,200 kg | 1.500 | 800.00 kg | 66.7% |
| 1,800 kg | 2.250 | 800.00 kg | 44.4% |
| 2,400 kg | 3.000 | 800.00 kg | 33.3% |
| 3,200 kg | 4.000 | 800.00 kg | 25.0% |
Questions
What is a good feed conversion ratio?
Entirely species-dependent. Broiler chickens and farmed fish commonly achieve 1.2 to 1.8, pigs 2.5 to 3.5 and beef cattle 6 or more. Within a species the useful comparison is against your own previous cycles and against published benchmarks for the same system.
Why do some species convert feed so much better?
Several reasons compound. Fish are ectothermic so they spend nothing on maintaining body temperature, and being supported by water they spend less on skeleton and posture. Ruminants carry the cost of fermentation, which loses energy as methane and heat, in exchange for digesting material monogastrics cannot use at all.
Should I use as-fed or dry matter weight?
Either, but consistently, and say which. As-fed is the common convention and the easier measurement. Dry matter FCR is more comparable across feeds of different moisture content, and the two figures differ substantially for wet feeds.
Does FCR account for mortality?
Not in this form. Feed consumed by animals that later died still appears in the numerator while contributing nothing to the gain, so mortality worsens the apparent FCR. That is arguably correct as a measure of what the operation actually consumed, but it does mix two different problems into one number.
For corn yield estimation on the cropping side, see the corn yield calculator. For field work rates, see the acres per hour calculator.