How to use the horse hay needs calculator
- Enter your horse's weight and the hay's dry matter percentage.
- Optional: add bale weight and price for bales and cost.
- Press Calculate.
Worked example
A 500 kg horse eating hay that is 90% dry matter, from 20 kg bales costing US$12.
- Horse weight
- 500 kg
- Hay dry matter (%) — from the hay analysis or supplier
- 90
- Bale weight — optional
- 20 kg
- Price per bale — optional
- 12
- Typical range
- 8.3–13.9 kg a day
- Dry matter share
- 1.5–2.5% of body weight
- Maximum intake
- up to about 16.7 kg a day (3% of body weight as dry matter)
- Bales per month
- about 13–21
- Hay cost per month
- about $152–$253
This is how much horses typically eat, not how much yours should. Weigh a few bales and ask your vet or an equine nutritionist.
Example values are illustrative; this result is produced by the same calculator above.
How we calculate it
Sources: Alabama Cooperative Extension · Merck/MSD Veterinary Manual
Understanding your result
Horses are grazing animals that eat many hours a day. Extension summaries of the NRC (2007) say horses typically eat about 1.5 to 2.5% of their body weight in forage dry matter each day, depending on the horse and the forage. The Merck table footnote gives a maximum voluntary intake of 2.5 to 3.0%.
Hay is not all dry matter. Hay that is 90% dry matter is 10% water, so a 500 kg horse eating 1.5 to 2.5% of its weight as dry matter eats about 7.5 to 12.5 kg of dry matter, which is 8.3 to 13.9 kg of hay as fed. At the 3% maximum that is up to about 16.7 kg.
Add the bale weight and price and the calculator converts the range into bales and cost per month. It shows what horses typically eat, not what yours should eat; that depends on its weight, workload, condition and other feed.
Common mistakes
- Using dry matter percentages from a different hay.
- Assuming every bale weighs the label weight.
- Forgetting wasted hay when buying.
- Cutting forage sharply to lose weight; ask your vet.
- Treating the typical range as a prescription.
Good to know
- A hay analysis gives the dry matter percentage and nutrient content.
- Slow feeders can reduce waste and extend feeding time.
- Use the Horse Hay Cost Calculator if you already know how many kilograms you feed.
When to talk to your vet
- Your horse is losing or gaining weight
- Your horse stops eating
- Before changing a horse's diet
Frequently asked questions
Where does the 1.5–2.5% come from?
Extension summaries of the NRC (2007) say horses typically eat 1.5 to 2.5% of their body weight in forage dry matter each day, depending on the horse and forage quality. The Merck table footnote gives a maximum intake of 2.5 to 3.0%.
What is hay dry matter?
The share of the hay that is not water. Hay analyses report it; if you do not have one, ask your supplier.
Is this how much I should feed?
It is the range horses typically eat. How much your horse should eat depends on its needs, so ask your vet or an equine nutritionist.
What if I do not know the dry matter?
Ask your hay supplier or send a sample for analysis. The calculator needs it to turn dry matter into kilograms of hay.
Why is there a maximum figure?
The Merck table footnote gives a maximum voluntary intake of 2.5 to 3.0% of body weight as dry matter, so the calculator shows the 3% upper limit.
Does it include grain or pasture?
No. It covers forage as hay only. Pasture and other feed reduce the hay a horse needs.
Sources
- Alabama Cooperative Extension — Decreasing costs of feeding horses (forage intake of 1.5–2.5% of body weight as dry matter)
- Merck/MSD Veterinary Manual — Estimated Average Minimum Daily Nutrient Requirements of Mature Horses and Ponies (table adapted from NRC 2007)
Related calculators
- Horse Weight CalculatorEstimate your horse's weight from its heart girth and body length with a tape measure.
- Horse Hay Cost CalculatorWork out how long a bale lasts and what hay costs per day, month and year.
- Horse Maintenance Nutrients CalculatorSee the daily minimum energy, protein, calcium, phosphorus and vitamin A a mature horse needs for maintenance, from its weight.
- Lactating Mare Nutrients CalculatorSee the daily minimum energy, protein, calcium and phosphorus range a lactating mare needs, from her weight and the stage of lactation.
Shows how much horses typically eat, not how much yours should. Ask your veterinarian or an equine nutritionist. If your pet may have eaten something harmful, contact your vet or an animal poison helpline now.