Winter hay calculator
How much hay, and how many bales, do my animals need for winter?
Showing for United States
Dry matter to have on hand, with loss
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- Dry matter to have on hand, with loss
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- The same, in tons of 2,000 lb (or tonnes if you weigh in kilograms)
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- Hay as fed, with loss
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- Hay as fed, in tons of 2,000 lb (or tonnes if you weigh in kilograms)
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- Dry matter eaten a day
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- Dry matter eaten over the feeding days, before loss
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- Dry matter in one bale
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Dry matter is the hay with its water taken out. Animals need dry matter; you buy and stack hay as fed.
This does not allow for extra hay in cold weather or for poorer hay, as NDSU Extension also notes.
Bales are rounded up to a whole bale, so you do not run short.
A planning estimate from your own figures. A forage test, your vet or your extension office can refine it.
Dry matter in the bale
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- The bale as it comes
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- Volume (cubic feet, or cubic metres if you weigh in kilograms)
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Measure in feet with pounds per cubic foot, or in metres with kilograms per cubic metre, to match the weight unit you chose.
Dry matter is the hay with its water taken out. Animals need dry matter; you buy and stack hay as fed.
A planning estimate from your own figures. A forage test, your vet or your extension office can refine it.
Enter your numbers to see the result.
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How this is worked out
Each day, the animals eat dry matter equal to their total body weight times your intake percentage. Over the feeding days, with your loss percentage added on top, that is the dry matter to have on hand. Tons are 2,000 lb if you weigh in pounds, or tonnes of 1,000 kg if you weigh in kilograms. Hay as fed is the dry matter divided by its dry-matter percentage. A bale's dry matter is its weight times its dry-matter percentage, and the bales needed are the dry matter to have on hand divided by that, rounded up to a whole bale. A round bale's volume is π times half its diameter squared times its width, and its dry matter is the volume times the dry matter packed into each cubic foot (or cubic metre if you weigh in kilograms). This follows NDSU Extension's method (2022) for hay needs and University of Missouri Extension's (2025) for bale weight.
A worked example
Example numbers only; use your own. NDSU Extension's example herd of 175 cows at 1,350 lb, 8 bulls at 1,800 lb and 26 heifers at 670 lb, eating 2.5% of their weight a day in dry matter, needs 6,701.8 lb a day. Over 210 days with 15% loss on top, that is 1,618,473 lb of dry matter, or 809.24 tons. Bales of 1,400 lb at 88% dry matter hold 1,232 lb each, so you need 1,314 bales. NDSU's article rounds to 6 bales a day along the way and so prints a higher count; this calculator rounds only at the end. A 5 ft by 5 ft round bale packed at 9 lb of dry matter per cubic foot holds about 884 lb of dry matter.
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