Feed Conversion Ratio (FCR) Calculator

What feed conversion ratio measures

Feed conversion ratio answers one question: how many pounds of feed did it take to add one pound of live weight? Divide total feed by total gain and you have it. A pen of steers that ate 360,000 lb of ration and gained 60,000 lb has an FCR of 6.0, meaning six pounds of feed bought each pound of gain.

The ratio matters because feed is normally the largest single variable cost in a livestock enterprise, and because FCR multiplies straight into money. Feed cost of gain is nothing more than FCR times the price of a pound of feed. If your ration costs $240 a ton, that is $0.12 a pound, so an FCR of 6.0 means $0.72 of feed in every pound of gain. Shave the ratio to 5.7 and the same ration buys that pound for $0.684 — a saving of 3.6 cents per pound, or $21.60 on a steer that gains 600 lb.

Two conventions travel with the number and you must state both. The first is moisture basis: an as-fed ratio and a dry matter ratio for the same pen differ by the dry matter fraction, so a wet ration always shows a larger as-fed number than the same nutrition delivered dry. The second is direction: feed conversion ratio is feed ÷ gain, so lower is better, while feed efficiency is its reciprocal, gain ÷ feed, so higher is better. Poultry and swine work almost universally in FCR; some cattle records report gain-to-feed. This calculator reports both so there is no ambiguity.

The arithmetic and the three conversions around it

The core formula is deliberately simple; the care goes into what you put in it.

Total gain. Multiply gain per head by head count: (out weight − in weight) × animals. Both weights must use the same shrink convention. Cattle weighed off pasture full and weighed in again after an overnight stand differ by several percent of body weight for reasons that have nothing to do with growth, and a two-percent shrink difference on a 1,350 lb steer is 27 lb, which is 4.5% of a 600 lb gain and moves the ratio by the same proportion.

Total feed. Everything delivered to that group, as fed, over the same window. Feed removed and fed elsewhere comes out. Feed in the bunk on the last day is a judgement call that should be made the same way at the start and the end so the two errors cancel.

Dry matter restatement. Multiply the as-fed ratio by the dry matter fraction. This is the only way to compare a corn-silage-based feedlot ration at 55% dry matter with a dry pelleted diet at 89%. Two pens with identical dry matter conversion will show as-fed ratios differing by the ratio of their dry matters, and neither pen is doing anything differently.

Cost of gain. Multiply FCR by the price of a pound of feed. Feed price per ton divided by 2,000 gives price per pound. Note that this is feed cost of gain, not total cost of gain: yardage, health, interest and death loss are separate lines and this calculator does not touch them.

How to read the number you get

The only comparison that means anything is against your own history on the same species, the same weight range, the same ration moisture and the same weighing convention. FCR rises with body weight in every growing animal, because maintenance takes a larger share of intake as the animal gets bigger and because later gain contains more fat, which costs more energy per pound to deposit than lean tissue does. A pen finished to a heavier out-weight will therefore show a poorer whole-period ratio than the same cattle sold lighter, and that is biology, not management.

Species sit in very different places for the same reason. Fish and poultry, which are young, small and lean at slaughter, convert far more tightly than finished cattle. Comparing across species tells you about physiology; comparing within a species and weight range tells you about your operation.

When a ratio moves between closeouts, work through the inputs before you conclude anything about the animals. Was the in-weight taken on the same shrink? Did feed for a second pen get charged to this one? Did the ration moisture change without the dry matter being re-tested? Only once those are clean is the difference a real biological signal, at which point the usual causes are ration energy density, health events, weather and implant or feed-additive strategy.

Feed cost of gain by conversion ratio and feed price

Feed only. Yardage, veterinary cost, interest, death loss and marketing are not included, so this is a floor under the true cost of gain rather than the whole of it.

Mistakes that corrupt a conversion ratio

• Mixing moisture bases. Comparing an as-fed ratio from a silage ration with a dry matter ratio from a pelleted one is the most common error in the whole subject. State the basis every time you quote a number.
• Inconsistent shrink on the scale. Weighing in full and out shrunk inflates the apparent gain; the reverse deflates it. Use one convention and record it with the closeout.
• Charging the wrong feed to the pen. Loads split between groups, refusals moved to another pen and feed left in the bunk at closeout all belong to somebody, and the ratio is only as clean as the accounting.
• Forgetting mortality. Animals that died ate feed but contributed no out-weight. Decide whether you are reporting a deads-in or deads-out ratio and label it.
• Reading FCR as efficiency. A larger FCR is a worse result; a larger feed efficiency is a better one. They are reciprocals, so 6.0 and 0.1667 are the same fact.
• Comparing across weight ranges. Whole-period ratios from pens finished to different out-weights are not directly comparable, because the ratio for any single increment of gain worsens as the animal gets heavier.

Related measures and where to go next

FCR is one of three numbers that describe the same closeout, and each answers a different question. Average daily gain tells you how fast; the average daily gain calculator isolates it. Feed conversion tells you how efficiently. Cost of gain tells you what it was worth. A pen can gain quickly and convert poorly if it is being pushed on an expensive ration, and a pen can convert beautifully while gaining too slowly to pay yardage.

Two refinements are worth knowing. Residual feed intake compares an animal's actual intake with the intake predicted from its size and growth, and it separates genetic feed efficiency from the effect of body weight in a way FCR cannot. Feed efficiency on a carcass basis divides feed by carcass gain rather than live gain, which removes the distortion caused by differing dressing percentages and gut fill.

To set the intake side of the equation before a pen closes out, use the dry matter intake calculator. To build the ration itself from two ingredients, use the Pearson square feed ration calculator. If the feed is hay coming off your own ground, the hay tonnage per acre calculator tells you whether you have enough of it.