Hay calculator: how many bales do your animals need?
Running short of hay in late winter is expensive, and buying far too much ties up money and barn space. This hay calculator works out how much hay your cows, buffalo, horses, goats or sheep will eat over a feeding period, in pounds and tons or kilograms and tonnes, and turns it into a number of bales of the size you buy or make.
It starts from each animal’s daily dry-matter intake — a percentage of body weight — converts dry matter into hay as fed, and adds an allowance for storage and feeding waste. Add your hay yield to see how many acres or hectares you need to cut, and a price to see the cost.
How to use the hay calculator
- Choose US units (lb, tons, acres) or metric (kg, tonnes, hectares).
- For each group of animals, pick the type, how many and their average weight. The usual dry-matter intake fills in; change it if you know better.
- Enter the number of feeding days and, if they also graze or get silage, the share of the diet that comes from hay.
- Check hay dry matter (85% is typical) and the waste you expect, and set the bale weight — weigh a few bales if you can.
- Read the bales and tons needed, the daily amount per animal, the land needed and the cost.
Hay Requirement Calculator features
Several groups at once
Up to three groups — for example cows, horses and goats — added together.
Species defaults
Dry-matter intake of 2.5% of body weight for cattle and buffalo, 2% for horses, 3.5% for goats and 3% for sheep, all editable.
Dry matter and waste
Converts dry matter to hay as fed and adds your waste allowance, the two steps most rough guesses leave out.
Bales, tons and acres
Whole bales to buy, tons or tonnes, and the acres or hectares of hayfield at your yield.
US or metric
Switching units converts the weights you have typed.
The hay formula with an example
Hay per day (as fed) = number of animals × body weight × dry-matter intake % × share from hay ÷ hay dry matter % × (1 + waste %).
- 20 beef cows weighing 1,200 lb eat 2.5% of their weight as dry matter: 20 × 1,200 × 0.025 = 600 lb of dry matter a day.
- Hay is about 85% dry matter: 600 ÷ 0.85 = 706 lb of hay as fed.
- Add 15% for storage and feeding loss: 706 × 1.15 = 812 lb a day.
- Over 150 days of winter: 812 × 150 = 121,765 lb = 60.9 tons, or 122 round bales of 1,000 lb.
How much hay do cows, horses, goats and sheep eat?
Ranges are from Oregon State University Small Farms and the Iowa Beef Center; lactating, growing and late-pregnant animals eat at the top of the range. For a complete dairy ration with concentrate, use the cattle feed calculator; to estimate weights without a scale, use the cattle weight calculator or the horse weight calculator.
| Animal | Dry matter, % of body weight | Example per day (as fed, 85% DM) |
|---|---|---|
| Beef cow, 1,200 lb | 2–2.5% | about 28–35 lb (13–16 kg) |
| Dairy cow or buffalo, 450 kg | about 2.5–3% | about 13–16 kg |
| Horse, 1,000 lb | 1.5–2.5% | about 18–29 lb (8–13 kg) |
| Goat, 100 lb | 3–5% | about 3.5–6 lb (1.6–2.7 kg) |
| Sheep, 150 lb | 2–4% | about 3.5–7 lb (1.6–3.2 kg) |
Cutting waste
- Feeding round bales with no feeder can waste more than half of the hay; in Missouri research a hay ring with only a 7-day supply put out kept waste under 6%.
- Feed only a few days’ supply at a time and put feeders on a well-drained pad.
- Test the hay: low-quality hay is eaten in smaller amounts and may need a supplement even when the quantity looks right.
Hay Requirement Calculator FAQ
How many bales of hay does a cow need for winter?
A 1,200 lb cow eating 2.5% of her weight as dry matter needs about 35 lb of hay a day, or about 40 lb with 15% waste. Over 150 days that is about 6,000 lb — six round bales of 1,000 lb or about 120 small square bales of 50 lb.
How much hay does a horse eat per day?
Usually 1.5–2.5% of its body weight, about 20 lb a day for a 1,000 lb horse, more if it has no pasture.
How much hay does a goat eat?
About 3–5% of body weight in dry matter — 3 to 5 lb of hay a day for a 100 lb goat.
How do I calculate hay per acre?
Divide the tons of hay you need by your yield per acre. 60 tons at 2 tons per acre needs 30 acres; enter your yield in the calculator to see acres and bales per acre.
Why add waste?
Hay is lost in storage (weathering, mould) and at feeding (trampling, refusal). University guidance suggests allowing 10–50% depending on storage and feeders.
Does the hay calculator work in kilograms?
Yes. Choose kg, tonnes, hectares; the weights you typed are converted.