Hay Bale Calculator
Work out how many bales a herd needs, or how many a field will yield.
Please note: Planning figures based on published averages. Soil type, climate, variety, season and local practice all shift these results substantially. Base real decisions on a soil test, local extension guidance and the product label — particularly for fertiliser, lime and any crop protection product, where the label is a legal document.
What the Hay Bale Calculator does
Winter feed budgets convert daily intake into bale counts. The two variables that trip people up are dry matter — hay is about 85%, so the weight fed exceeds the nutritional weight — and bale weight itself, which varies enormously between machines and seasons.
Formula
Hay per head per day = Bodyweight × Intake % ÷ 100 ÷ 0.85Total = Per head × Head × Days × (1 + Wastage)Bales = ⌈Total ÷ Bale weight⌉Yield mode: Bales = Yield × Area ÷ Bale weight
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Calculate | one of 2 options | Yes | — |
| Animal class | one of 11 options | In some modes | Shown Calculate is Bales needed to feed stock. |
| Number of animals | number | In some modes | Accepts 1 or more. Shown Calculate is Bales needed to feed stock. |
| Days to feed | number | In some modes | Accepts 1 or more. Shown Calculate is Bales needed to feed stock. |
| Field area | number | In some modes | Accepts more than 0. Shown Calculate is Bales a field will produce. |
| Field area unit | one of 4 options | In some modes | Shown Calculate is Bales a field will produce. |
| Hay yield | t/ha | In some modes | Accepts more than 0. Shown Calculate is Bales a field will produce. |
| Weight per bale | kg | Yes | Accepts more than 0. |
| Feeding wastage | % | Optional | — |
| Price per bale | selected currency | Optional | Accepts 0 or more. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Calculate and Currency.
- Enter Weight per bale.
- Fill in the remaining inputs the form shows for your choice.
- Optionally add Feeding wastage and Price per bale.
- Select Calculate.
Worked example
Fifty beef cows fed hay for 120 days, 500 kg round bales, 10% wastage.
- Class
- Beef cow
- Head
- 50
- Days
- 120
- Bale
- 500 kg
- Wastage
- 10%
13.75 kg DM a head becomes 16.2 kg of hay as fed. Over 120 days with wastage that is 106.8 tonnes — 214 bales.
Reading the result
- "Days one bale feeds the herd" turns the total into a practical, checkable number at feed-out — useful for confirming actual usage matches the plan as winter progresses.
- The bale-weight sensitivity table shows how much the required bale count shifts across a realistic weight range — since a nominal "500 kg" bale can really run 400–700 kg, the count alone is only as reliable as that assumption.
Assumptions and limitations
- Hay dry matter is assumed to be a fixed 85% — actual bale density and moisture vary, and hay baled wetter than assumed has a lower true dry-matter share than this figure models.
- Wastage is applied as a single flat percentage regardless of feeder type, though the notes cite a 10–40% range depending on the feeding method used.
Common mistakes
- Using an assumed bale weight without ever weighing an actual bale, then discovering partway through winter that the true weight was meaningfully lighter or heavier, throwing off both the day-count and the remaining feed budget.
Frequently asked questions
How much does a round bale weigh?
A 5 ft round bale of dry hay is typically 450–550 kg, but density and moisture swing it widely. Weighing a sample is worth the trouble.
How much wastage should I allow?
10–15% with a good ring feeder, 20% with a poor one, and up to 40% feeding on bare ground.