Start from the animal, not from the barn
The chain is short. Each animal eats some pounds a day, there are so many animals, the feeding period is so many days, and some fraction of what you buy never reaches an animal. Multiply, then divide by what one bale weighs. The reason people still get it wrong is that three of those four numbers are usually estimated and two of them are estimated optimistically.
Ration is commonly expressed as a percentage of body weight, in the region of 2 to 3 percent as fed for maintenance, which puts an 1,100 lb animal somewhere near 25 to 33 lb a day. That range is orientation rather than a prescription: growth, late gestation, lactation, cold weather and forage quality all move it, sometimes substantially. The figure for your animals comes from your veterinarian or extension livestock agent looking at the animals and, ideally, at a forage test on the hay itself.
Bale weight is not a constant and never was
A bale is a shape, not a quantity. Small square bales commonly fall somewhere in the region of 40 to 70 lb, and large round bales anywhere from roughly 700 to 1,500 lb depending on diameter, width, density and moisture. That is a spread of more than thirty to one across the two types, and a spread of nearly two to one within each of them. A price per bale is therefore almost meaningless as a comparison; price per ton is the only figure that lets a small square and a round bale be compared, which is why the calculator produces it when you enter a bale price.
Weigh a sample from the lot you are buying. A livestock scale, a pallet scale, or the difference between two trips across a truck scale will all do. Two bales of the same nominal size from different balers, or from the same baler on a damp morning and a dry afternoon, can differ by a third. Moisture is part of that difference and it is not feed value, so hay bought wet is partly bought water.
Where the waste goes
Waste has two separate sources and people usually count neither. Storage loss happens between baling and feeding: weathering on bales stored outdoors uncovered, spoilage on the bottom layer sitting on bare ground, and dry matter loss to respiration in bales put up too wet. Feeding loss happens at the animal: hay pulled out of a rack and trodden on, rolled-out bales fouled and refused, and sorting where animals eat the leaf and leave the stem.
| Situation | Loss commonly quoted | Main cause |
|---|---|---|
| Barn stored, fed in a well-designed feeder | Under 5% | Ordinary sorting and refusal |
| Tarped or covered outside, fed in a ring | 10-15% | Edge weathering, some trampling |
| Round bales outdoors on the ground, fed on the ground | 30-40% or more | Bottom spoilage, weathering, trampling and fouling |
The gap between the top and bottom rows is frequently larger than the cost of a hay shed amortised over a few winters, which is the calculation worth doing before deciding storage is too expensive.
Footprint, stacking and the ceiling
Footprint comes out of the bale plan area, the number of tiers and an access allowance. It is deliberately simple, because the constraints that decide a real stack are not geometric. Stack height is limited by what you can lift, what you can get down again safely, and by the building: hay is heavy, and a mow floor or a loft has a load limit that a full stack can exceed. Bales fall, and people are injured by them regularly.
The other reason not to fill a space to its ceiling is heat. Hay cures in the stack and generates heat doing it, and hay baled above safe moisture can heat enough to be a genuine fire risk in the first weeks. Airflow through and around the stack matters, monitoring temperature in the first month matters, and moisture at baling matters most of all. Your extension office publishes safe moisture figures by bale type, and they are worth reading before the first load goes in rather than after.
Ordering, and the margin nobody regrets
Buy for a long winter. A feeding period is an estimate of when pasture stops and when it starts again, and the second half of that is a guess about spring weather made in autumn. Hay left over stores through a summer under cover with modest loss; hay bought short in March is bought in a sellers’ market at whatever the price has risen to. A margin of a few weeks costs a small percentage. Running out costs whatever it costs that year.
The other half of the year is the pasture stocking and rotation calculator, and running both together is how you find out whether the herd size works at all rather than only in July. For stacking volume arithmetic in a different context, the firewood cord calculator handles the same kind of stack-and-void problem. If the flock end of the operation needs feeder space, the chicken coop size calculator covers it.
Questions people ask
How many bales of hay does a horse or cow need for winter?
It depends on the animal's weight, the ration and the bale weight, which is why all three are inputs. As an illustration of the arithmetic rather than a recommendation: an 1,100 lb animal fed at 2.5 percent of body weight eats about 27.5 lb a day, so 150 days is roughly 4,125 lb fed, and with 15 percent waste around 4,750 lb to buy. At 50 lb per small square that is 95 bales for one animal; at 1,000 lb per round bale it is five. The ration figure itself is not something to take from a web page. Body condition, stage of production, weather and hay quality all move it, and your veterinarian or extension livestock agent should set it after seeing the animals.
How much does a round bale weigh?
Roughly 700 to 1,500 lb is the range usually cited, and that is too wide to plan on. Weight depends on diameter, width, how tightly the baler packed it, the forage species and the moisture content, and the moisture part is not feed. A 4x5 bale and a 5x6 bale differ by a large factor even at the same density, because volume goes up with the square of diameter. The only reliable answer is to weigh several bales from the lot you are actually buying and average them. If you are comparing prices between suppliers or between bale types, convert to price per ton, because price per bale compares nothing at all.
How much hay is wasted, really?
Anywhere from under 5 percent to more than 40, and the difference is almost entirely storage and feeder design rather than the animals. Barn-stored hay fed in a well-designed feeder loses very little beyond ordinary sorting. Round bales stored outdoors on bare ground and fed on the ground lose to bottom spoilage, weathering through the outer layer, trampling and fouling, and the commonly quoted figures for that combination run 30 to 40 percent. The practical consequence is that the cheapest hay is often the most expensive: paying more for hay you can store under cover and feed in a ring can easily cost less per pound actually eaten. Run the calculator at both waste figures and compare the tonnage.
How much floor space does a season of hay take?
The calculator works it from your bale dimensions, the number of tiers and an access allowance, and the answer is usually larger than people picture. Small squares at 3 by 1.5 ft stacked six high need about a quarter of a square foot of floor per bale, so a few hundred bales is a substantial part of a small barn once you add aisles. What limits the stack in practice is rarely the arithmetic. It is what a person can lift to the top tier and get down again safely, and the load the floor can carry, which on a loft or a mow is a real limit and not a generous one. Stacked hay also needs air around it while it cures.
Should I buy hay by the bale or by the ton?
By the ton wherever you can, because it is the only unit that means anything. A bale is a shape and its weight varies by a factor of two within a single type and by thirty across types, so a price per bale tells you nothing about the price of feed. Enter your bale price in the calculator and it returns a price per ton, which is what lets you compare a small square supplier against a round bale supplier honestly. The remaining variable is quality, and that is not visible in either unit. A forage test tells you the actual nutritional content, which is the difference between hay that meets an animal's needs and hay that fills it up, and your extension office can point you at a lab.