What it means
Feed is a major input in livestock and aquaculture, and the feed conversion ratio helps managers see how much feed is used to produce growth. For a weight-gain version, divide feed used by net live-weight gain over a stated period, so 17,000 kilograms of feed for 10,000 kilograms gained gives an FCR of 1.7.
State whether feed is measured as offered, consumed or purchased. The denominator can vary, since a farm might use live-weight gain, harvested biomass or saleable meat, and those are not equivalent.
A dairy may instead report kilograms of feed per litre of milk, which should be labelled separately. Mississippi State University describes farm-level catfish FCR as feed fed divided by fish sold, which can exceed an experimental feed-to-weight-gain value because mortality and feed waste change the farm result.
The ratio needs a consistent time period, because opening and closing animal weights, arrivals, sales and deaths affect calculated gain. A snapshot of feed purchases divided by final weight can mix periods and misstate efficiency.
Weighing and recording accuracy matter too: a faulty scale, estimated feed deliveries or uncounted animal movements can shift the ratio, so audit the data before changing feeding practice. Feed quality matters as well as quantity, since a cheaper ration might reduce feed price per kilogram but worsen growth or health, so compare total feed cost per unit of saleable output, not only the FCR.
Species and age matter, as young animals can convert feed differently from older ones, fish, poultry and cattle cannot be ranked by one universal number, and housing, temperature and genetics also affect results. Feed offered is not always feed eaten, because spillage, uneaten pellets and storage losses raise the amount recorded against production, so an apparent biological problem may be a feeder or inventory-control problem.
Animal health also affects the ratio, because disease can slow gain or increase mortality, leaving earlier feed without saleable output. A lower FCR is often useful but not the only goal, since very restricted feeding can reduce growth, delay sale or harm animals.
Global Seafood Alliance describes FCR as total feed use divided by net aquaculture production while noting that the metric alone can mislead on environmental impact, as feed composition and nutrient discharge are separate issues. A ratio of 1.7 means 1.7 kilograms of feed per kilogram of defined output, not that 70% of feed was wasted, and profit also depends on feed price, animal price, mortality and fixed costs, so calculate contribution per batch.
Track FCR by batch or house, publish it with its definition of species, stage, period, feed basis and output, and use a dashboard of feed used, net gain, deaths, days to market and cost per saleable kilogram without crowding out safety or welfare. If FCR rises on an invented poultry farm after a heat event, the manager checks water, feed logs and mortality before blaming the supplier, and a veterinarian or nutrition specialist can help identify feeding, disease or environment causes, because one KPI alone should not drive a major ration change.
In practice
Real-world examples.
Example
An invented poultry flock uses 17,000 kilograms of feed for 10,000 kilograms of live-weight gain, giving an FCR of 1.7. The manager records the period dates and the feed basis next to the figure. Next month's batch is compared on the same terms.
Example
A fish farm tracks feed fed and harvested biomass while separately recording mortality. Because fish that die consume feed but are never sold, the farm-level ratio is higher than a ratio based only on survivors' weight gain. The farm reports both figures.
Example
A dairy labels its efficiency measure as kilograms of feed per litre of milk instead of comparing it directly with a meat weight-gain FCR. The two measures describe different outputs. The dairy compares each herd only with its own earlier results.
Formula
Calculation
Weight-gain FCR = kilograms of feed used / kilograms of net live-weight gain. State the feed and output bases before comparing values.
Worked example: a flock starts the period at 2,000 kilograms of live weight and ends at 12,000 kilograms, so net gain is 12,000 - 2,000 = 10,000 kilograms. It uses 17,000 kilograms of feed, so FCR = 17,000 / 10,000 = 1.7.
Cost example: if Ration A costs $0.40 a kilogram, feed cost is 17,000 x $0.40 = $6,800, or $6,800 / 10,000 = $0.68 per kilogram of gain. A competing Ration B costs $0.45 a kilogram and achieves an FCR of 1.6, giving 1.6 x $0.45 = $0.72 per kilogram of gain. Ration B has the better FCR, yet it is $0.04 more expensive per kilogram gained, which is why FCR and cost are compared together.Case study
Seen in the real world.
This entirely fictional case follows Sahara Poultry, an invented farm. FCR increased in two houses, and staff first suspected a new ration from the supplier. The team instead checked feeder waste, heat records and animal health with a specialist before changing feed.
They found that a week of high temperatures had reduced growth and that damaged feeders were spilling pellets. Repairs and cooling adjustments were made and the team kept tracking FCR by house over the next batches. No reduction or cash saving is asserted, and the case is illustrative only.
Watch out
Common mistakes.
- Mixing feed purchased in one period with weight gain from another.
- Comparing different species, ages or output definitions without context.
- Treating a lower FCR as proof of better profit or welfare.
Questions
People also ask.
What is a good FCR?
It depends on species, age, system, feed basis and output. Compare like groups and relevant evidence.
Why does mortality affect farm FCR?
Feed consumed by animals that die may not produce saleable output, increasing feed per unit sold.
How can a farm improve it?
Investigate feed use, health, environment and handling with appropriate specialists, then test changes.
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