A feed conversion ratio calculator answers one question: how many units of feed did it take to put on one unit of liveweight? It is the most quoted number in livestock production and one of the most casually misquoted, because two people can compute it from the same pen and get answers a full point apart depending on whether they used dry matter or as-fed weights, whether they counted refusals, and what they did about the animals that did not finish the period.
This page computes the ratio and the numbers that sit underneath it — average daily gain, average daily feed intake, gain per unit of feed and a feed cost per unit of gain — and then spends most of its length on the part that actually matters, which is the conditions under which one ratio can be compared to another. Arb Digital publishes free calculators that show their working, and this is a case where the working is more valuable than the answer.
What This Feed Conversion Ratio Calculator Does
Enter the number of animals, the days on feed, the total feed the group consumed, the starting and ending weight per head, a feed price and a reference ratio to compare against. The calculator returns the feed conversion ratio, average daily gain per head, average daily feed intake per head, the reciprocal figure of gain per unit of feed, and the feed cost of producing one pound of liveweight gain. Two bars set your ratio next to the reference you entered, scaled against whichever is larger.
Everything is computed on the group and then divided down, which is the correct order. Working out a ratio per head first and then averaging the ratios gives a subtly different and less meaningful answer, because it weights a light animal's efficiency the same as a heavy one's when the heavy one ate more of the feed.
How to Use It
- Count the animals and the days. Use the head count that was actually on feed for the period. Where animals were removed part way through, the honest approach is to work in animal-days rather than head, and to say so whenever you quote the result.
- Enter total feed consumed, not feed delivered. Subtract refusals, spillage and any feed that went into a different pen. Delivered feed flatters nothing and distorts everything.
- Enter start and end weights per head. Both should be measured the same way, at the same time of day, with the same shrink assumption applied or not applied to each.
- Add a feed price if you want the cost line. Feed cost per pound of gain is usually a more decision-relevant number than the ratio itself, because it converts an efficiency figure into money.
- Set the reference to something real. Your own figure from last cycle is a better comparison than a published average from a different species, diet and climate.
The Formula / How It's Calculated
The core definitions are straightforward. Total gain = (ending weight − starting weight) × head. Feed conversion ratio = total feed ÷ total gain. Average daily gain = (ending weight − starting weight) ÷ days. Average daily feed intake = total feed ÷ head ÷ days. Gain per unit of feed is the reciprocal of the ratio, and feed cost per unit of gain is the ratio multiplied by the feed price. A useful identity falls out of these: FCR is also ADFI divided by ADG, which is a good arithmetic check on any result.
Worked through the values the page loads with: 100 head, 154 days, 63,800 lb of feed, 55 lb in and 275 lb out. Gain per head is 220 lb, so total gain is 22,000 lb and the feed conversion ratio is 63,800 ÷ 22,000 = 2.90. Average daily gain is 220 ÷ 154 = 1.43 lb/day. Average daily feed intake is 63,800 ÷ 100 ÷ 154 = 4.14 lb/day, and 4.14 ÷ 1.43 returns 2.90, as it must. Gain per pound of feed is 1 ÷ 2.90 = 0.345 lb, and at 14 cents a pound the feed cost of a pound of gain is 2.90 × 0.14 = $0.41, against a total feed bill of $8,932.
Penn State Extension's guide to adjusting and monitoring meat animal growth rate sets out the same two definitions — average daily gain as total weight gain divided by days between weights, and feed conversion as the relationship between feed consumed and weight gained — and works a pig example that lands on an ADG of 1.43 lb/day and an FCR of 2.9, which is where the defaults above come from.
The Ratio Is Not Comparable Unless the Basis Matches
This is the single most important thing on the page. A feed conversion ratio computed from as-fed weights on a wet ration and one computed from dry matter weights on a dry ration are different measurements wearing the same name. A total mixed ration at 45% dry matter weighs more than twice what its dry matter does, so an as-fed ratio on that ration will be more than double the dry matter ratio for exactly the same animal performance.
Published figures are usually quoted on a dry matter basis, and the ratios that circulate in conversation usually are not. Before comparing your number to anyone else's, establish which basis each was measured on, and convert if necessary — our dry matter calculator handles that conversion directly. The same discipline applies to the weight range: a ratio measured from 55 lb to 275 lb is not comparable to one measured from 150 lb to 275 lb, because efficiency falls as animals get heavier and a later start captures only the worse half of the curve.
Why Efficiency Falls as Animals Grow
Every animal spends part of its intake on maintenance before any of it becomes gain, and maintenance scales with body size. A heavier animal therefore burns a larger fixed cost each day before the first gram of growth, which is why the ratio worsens across a growing period even when the diet and the management never change. The composition of the gain shifts too: early gain is proportionally more lean tissue, which is largely water, and later gain carries more fat, which is energetically far more expensive to deposit per unit of weight.
Penn State's discussion of feed efficiency in dairy heifers shows the same pattern across a growth curve, publishing dry-matter-to-gain values that widen from around 2:1 for calves on milk through 3:1 to 4:1 for weaned calves and 4:1 for young heifers, out to 8:1 or more for older heifers on poor forage. Those are published reference points for a specific class of animal on specific diets, not benchmarks for anyone else's stock. The reason to know them is to understand that a rising ratio through a period is normal biology rather than a management failure.
What the Ratio Hides
Three things routinely disappear inside a feed conversion ratio and then reappear as a surprise in the accounts. The first is mortality and removals. Animals that died or were pulled still ate, and if their feed stays in the numerator while their gain leaves the denominator, the ratio degrades sharply for reasons that have nothing to do with how the survivors converted feed. Whichever convention you use, apply it consistently and state it. The animal mortality rate calculator covers that side of the arithmetic separately.
The second is time. Two groups can post the same ratio with a month between their finish dates, and the faster one has freed the pen, the labour and the capital a month earlier. Average daily gain, not the ratio, is the number that captures this. The third is price. A diet that improves the ratio by a tenth of a point while costing 20% more per pound has made the efficiency figure look better and the enterprise worse. Feed cost per pound of gain is the line that catches it, which is why the calculator computes it alongside.
Turning the Ratio Into a Decision
The ratio on its own does not support a decision, because it says nothing about what feed and liveweight are worth. Multiply it by the feed price and you have a cost of gain; compare that to the market price of the gain and you have a margin over feed, which is a number you can act on. Our break-even calculator and profit margin calculator handle the enterprise side of that arithmetic, and the crop yield calculator covers the cost of home-grown feed before it ever reaches a bunk.
A worked version: at an FCR of 2.90 and 14 cents a pound, gain costs 40.6 cents a pound in feed alone. Push feed to 18 cents and the same ratio produces 52.2 cents. Improving the ratio to 2.70 at the higher price gives 48.6 cents, which still does not recover the ground the price move took. That comparison, not the ratio in isolation, is what a feed change should be judged on.
Arb Digital builds and maintains free calculator libraries that earn organic search traffic, with every figure sourced to a named authority before it publishes.
Browse All Free Tools Talk To Arb DigitalCommon Mistakes to Avoid
- Mixing as-fed and dry matter weights. A wet ration measured as fed can more than double the ratio against the same animals measured on dry matter, which makes the comparison meaningless.
- Using feed delivered instead of feed consumed. Refusals and spillage belong out of the numerator, and leaving them in inflates the ratio without telling you anything about the animals.
- Comparing across different weight ranges. Efficiency worsens as animals get heavier, so a ratio that starts later in the growth curve will always look worse than one that starts earlier.
- Handling removals inconsistently. Deciding case by case whether a pulled animal's feed and gain stay in the calculation makes each period incomparable to the last.
- Optimising the ratio instead of the margin. A more expensive diet that improves conversion can still lose money per head, which only the cost of gain reveals.
Related Free Tools From Arb Digital
Convert wet feed weights before they reach this calculator with the dry matter calculator, cost home-grown rations with the crop yield calculator, and track losses separately with the animal mortality rate calculator. On the enterprise side, the break-even calculator and profit margin calculator turn a cost of gain into a margin, and the ratio calculator handles the general case. Browse the full free online tools hub for the rest.
Frequently Asked Questions
It is the weight of feed consumed divided by the weight of liveweight gained over the same period. A ratio of 2.9 means 2.9 pounds of feed went in for every pound of gain. A lower number means less feed per unit of gain.
Divide total feed consumed by total weight gained. Total gain is the ending weight minus the starting weight, multiplied by the number of animals. The same figure can be obtained by dividing average daily feed intake by average daily gain, which is a useful check.
They are reciprocals of each other. The conversion ratio is feed divided by gain, so lower is better. Feed efficiency is gain divided by feed, so higher is better. This calculator reports both so that a figure quoted either way can be compared.
Whichever basis you are comparing against, applied to both sides. Published figures are usually quoted on a dry matter basis. Mixing the two is the single biggest source of non-comparable ratios, because a wet ration weighs far more as fed than it does dry.
Maintenance requirements scale with body size, so a heavier animal spends more of each day's intake before any of it becomes gain, and later gain contains proportionally more fat, which costs more energy to deposit. A widening ratio through a growing period is expected biology rather than a management problem.
Consistently, and say which convention you used. Their feed is already in the total consumed, so leaving their gain out of the denominator worsens the ratio. Working in animal-days rather than head count is the usual way to keep periods comparable.
There is no universal answer, and this page does not offer one. Published values differ by species, class, diet, weight range and measurement basis, so the only comparison that carries information is against your own previous figure measured the same way, or against a published value for the same class of animal on a stated basis.
This calculator performs arithmetic on figures you supply. It sets no targets, prescribes no diets, and provides no nutritional or veterinary guidance; ration and management decisions belong with a qualified animal nutritionist or veterinarian.
