Hong Life CalculatorsUnderstanding the feed conversion ratio calculator — concept and principle
This calculator works out the feed conversion ratio (FCR), the kilograms of feed needed for each kilogram of live-weight gain, for a group of animals, together with feed efficiency, feed and gain per animal and the feed cost per kilogram gained. Poultry, pig, fish and cattle producers use it to track performance between batches.
How it is calculated
Weight gained = (final average weight − starting average weight) × animals at the end
FCR = total feed ÷ weight gained
Feed efficiency = weight gained ÷ total feed = 1 ÷ FCR
Feed cost per kg of gain = total feed × price ÷ weight gained
- Feed and weights are in kilograms; the price is per kg of feed in any currency.
- With a starting weight of 0 the result is the simple on-farm figure: total feed ÷ live weight sold.
The principle
Animals use feed for maintenance, activity and growth. Only the part that ends up as tissue shows on the scale, so FCR measures how efficiently a group turns feed into saleable weight. Feed eaten by animals that died stays in the total, but their weight is not in the gain, so losses late in the period raise the FCR.
Worked example
Default inputs: 400 kg feed, 96 animals at the end, start 0.04 kg, final 2.6 kg, feed price 0.45 per kg.
- Gain per animal = 2.6 − 0.04 = 2.56 kg.
- Total gain = 2.56 × 96 = 245.8 kg.
- FCR = 400 ÷ 245.76 = 1.63; feed efficiency = 0.614.
- Feed per animal = 400 ÷ 96 = 4.17 kg.
- Feed cost per kg of gain = 400 × 0.45 ÷ 245.76 = 0.73.
How to read the result
Lower is better: an FCR of 1.63 means 1.63 kg of feed per kilogram of gain. Compare only groups of the same species, age and finishing weight, because FCR rises as animals get heavier. For example, a Cornell extension fact sheet gives about 2–2.5 lb of feed per lb of gain for Cornish Cross broilers. Feed cost per kg of gain links the figure directly to profit.
Common mistakes
- Forgetting to subtract the starting weight of young animals.
- Not weighing feed left in bins and troughs at the end.
- Leaving out feed eaten by animals that died, which hides mortality losses.
- Comparing FCRs of groups sold at very different weights.
Frequently asked questions
Is a higher or lower FCR better?
Lower. It means less feed for each kilogram of weight gained.
What is feed efficiency?
The inverse of FCR, kilograms of gain per kilogram of feed.
Why does FCR rise as animals grow?
Heavier animals spend more energy on maintenance, so each extra kilogram costs more feed.
Sources: Aviagen (Indian River), "Be Smart: Optimizing Broiler Feed Conversion Ratio" (2011) · Cornell Cooperative Extension, fact sheet "Tracking Broiler Flock Performance"