Hay Storage Loss Calculator
See how much of the stack disappears between baling and feeding, and what better storage would return.
Your numbers
net-wrapped, uncovered on the ground, 8 months, 40 in annual rainfall
23.2 % dry matter lost
- Hay lost
- 25.5 tons
- Bales that disappear
- 46 bales
- Value lost
- $3,573
- Spending $12,000 on better storage pays back in about 4.1 years at this hay value.
- Storage loss lands before the feeder, so it stacks on top of feeding waste: 20% in the stack and 15% in the ring leaves you 68% of what you baled.
- Quality falls with quantity. The weathered shell that rots is also the leafiest, highest-protein part of a grass bale.
Show the math
- Base loss for the method12.0% + (1.40%/month × 8 months) = 23.2%
- Adjusted for rainfall23.2% × 1.00 (40 in) = 23.2%
- Hay in storage200 bales × 1,100 lb = 220,000 lb (110.0 tons)
- Dry matter lost220,000 × 23.2% = 51,040 lb, or 46.4 bales
- Value of the loss25.5 tons × $140/ton = $3,573
- Saving with improved storage25.5 − 4.4 tons = 21.1 tons saved, worth $2,957 a year
Assumptions this calculator used
Nothing here is hidden. Change any figure you have better local data for.
Shed 3%, tarped gravel pad 6%, gravel alone 10%. Source: University of Kentucky Extension AGR-171 outside hay storage trials.
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How to calculate hay storage loss
Storage loss is not a single number — it depends on what the bale sits on, whether it is covered, how long it sits, and how much rain falls on it. Take a base loss for the method, add a monthly accumulation, scale it to your rainfall, then apply it to the tonnage in the stack.
Loss % = (base % + monthly % × months) × rainfall factor
Hay lost lb = bales × bale weight × loss %
Payback yrs = storage investment ÷ (tons saved × $/ton)
Worked example
Two hundred 1,100 lb net-wrapped bales sitting on the ground for eight months in a 40-inch rainfall region lose about 23% of their dry matter — 25 tons, the equivalent of 46 bales that never make it to a cow. At $140 a ton that is roughly $3,500 a year. Moving the same hay into a shed at 4% loss saves about 21 tons, or $2,900 a year, so a $12,000 shed returns the investment in around four years.
Common mistakes
- Judging loss by the crust. A weathered shell six inches deep on a 5 ft bale is a third of the bale's volume.
- Stacking uncovered bales in a pyramid. It looks tidy and it is the worst storage layout there is.
- Carrying hay over a second year outside. The second winter costs far more than the first.
- Storing on a low, shaded site. Drainage and airflow matter as much as the cover.
Dry matter loss by storage method and months stored
Typical dry matter loss for round bales in a 40-inch rainfall region. Losses run lower in the arid West and materially higher in the humid Southeast.
| Storage method | 3 months | 6 months | 9 months | 12 months |
|---|---|---|---|---|
| Enclosed shed or barn | 2% | 3% | 3% | 4% |
| Tarped on gravel or pallets | 5% | 6% | 8% | 9% |
| Tarped on bare ground | 9% | 11% | 13% | 15% |
| Uncovered on gravel or pallets | 11% | 13% | 16% | 19% |
| Net-wrapped, uncovered on ground | 16% | 20% | 25% | 29% |
| Twine-tied, uncovered on ground | 22% | 27% | 33% | 39% |
| Stacked in a pyramid, uncovered | 27% | 34% | 42% | 49% |
Calculators to run next
- Winter Hay CalculatorStart here when you need to size the stack for the winter before you buy.
- Round Bale Weight CalculatorUse when you are guessing at bale weight and every other hay number depends on it.
- Hay Bale CalculatorUse to convert between tons quoted by a seller and bales you actually load.
- Hay Cost Per Ton CalculatorUse to compare two loads priced per bale, or hay quoted at different moistures.
- Hay Waste CalculatorUse when deciding whether a cone ring or cradle feeder pays for itself.
- Hay Moisture CalculatorUse before comparing prices — wet hay carries tons of water priced as forage.
Guides that use this calculator
- Pricing Hay by the Ton Instead of by the BaleTwo loads at the same price per bale can differ 40 percent on cost per ton of dry matter. Here is the conversion.
Questions ranchers ask
How much hay is lost storing round bales outside?
Bales sitting on bare ground with no cover typically lose 15 to 35% of their dry matter over a winter, and losses over 50% have been measured on bales left through a full year in high-rainfall regions. Bales on gravel and covered lose 5 to 10%; bales in a shed lose 2 to 5%.
Why does hay stored on the ground lose so much?
Two reasons. The bottom of the bale wicks moisture out of the soil and rots from underneath, and the weathered outer shell absorbs rain that then supports microbial breakdown. Getting bales off the dirt onto gravel, pallets or old tires solves most of the problem for very little money.
Does a tarp pay for itself on hay?
Usually within one or two seasons if the alternative is bare ground. A tarp costing a few hundred dollars over a stack of 60 bales that would otherwise lose 20% instead of 8% saves several tons of hay a year. The labor of tarping and untarping in wind is the real cost.
How should round bales be lined up outside if I have no cover?
Set them in single rows running north-south on a well-drained site, butted end to end tightly, with at least three feet between rows so sun and wind reach the sides. Never stack them in a pyramid uncovered — that traps water between bales and creates the worst losses of any layout.
Does net wrap reduce storage loss compared with twine?
Yes, meaningfully. Net-wrapped bales shed water better and hold their shape, typically losing several percentage points less dry matter than twine-tied bales in the same conditions. Plastic twine at close spacing is intermediate. Neither substitutes for getting the bale off the ground.
How long can hay be stored before quality drops?
Properly cured hay in a shed holds feeding value for years, losing mostly carotene and vitamin A rather than energy or protein. Hay stored outside deteriorates continuously, so the second winter on a bale outside is usually far more expensive than the first.
Is storage loss the same as feeding waste?
No, and they compound. Storage loss happens before the bale reaches the feeder; feeding waste happens after. A bale that lost 20% in storage and then 15% in an open ring delivers only 68% of what you baled.
Does a hay shed make financial sense?
For most operations feeding more than about 150 to 200 bales a year, yes. A pole shed at $8 to $15 per square foot stores roughly one 5 ft bale per 30 square feet, and typically returns the investment over 8 to 15 years in saved hay — faster in wetter regions and at higher hay prices.
Protect the hay, then invest what you save in the herd
A gravel pad and a tarp routinely return more per dollar than almost anything else on a cow-calf operation. When that saving turns into buying power, Agrilot's registered Angus females and sport horses come with verified seller records and an independent condition report on every lot.