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Horse Feed Calculator
Use this free horse feed calculator to work out how much your horse should eat and drink each day. Enter your horse's weight, its workload, and the type of forage you feed, and the calculator estimates the daily hay or pasture, grain, total feed, and water your horse needs — in kilograms or pounds.
| Daily ration | Amount |
|---|---|
| Forage dry matter (1.8% of body weight) | 9.0 kg |
| Grass hay as fed | 10.0 kg |
| Grain / concentrate (0.5% of body weight) | 2.5 kg |
| Total feed as fed | 12.5 kg |
| Water | about 33 L |
How the horse feed calculation works
A horse is a grazing animal, and its digestive system is built around a near-constant intake of fiber. The starting point for every ration is therefore forage — hay or grass. Equine nutritionists express forage needs as a share of body weight, measured as dry matter, which is the feed with all the water removed. A horse needs forage dry matter equal to about 1.5 percent of its body weight when idle, rising to about 2 percent when it works hard. This calculator uses 1.5 percent for idle horses, 1.6 percent for light work, 1.8 percent for moderate work, and 2.0 percent for heavy and very heavy work.
Dry matter is not the same as the hay you put in the feeder. Hay is about 90 percent dry matter, so you divide the dry matter figure by 0.90 to get the as-fed weight: 9 kg of dry matter becomes 10 kg of hay. Fresh pasture is only about 20 to 25 percent dry matter, so the same 9 kg needs roughly 40 kg of fresh grass — which is why a horse on pasture must graze most of the day.
Hay as fed = forage dry matter ÷ 0.90
Pasture as fed = forage dry matter ÷ 0.22
Grain = body weight × 0% (idle) to 1% (very heavy work)
Water ≈ body weight × 0.05–0.10 L per kg
Grain, or concentrate, is the energy top-up. An idle horse needs none — forage alone covers its needs, and extra grain only adds weight and raises the risk of colic and laminitis. As work increases, so does the grain: about 0.2 percent of body weight for light work, 0.5 percent for moderate work, 0.8 percent for heavy work, and up to 1 percent for very heavy work such as racing or eventing. A 500 kg horse in moderate work therefore gets 2.5 kg of grain a day. Split grain into at least two meals, and never feed more than about 0.5 percent of body weight in a single meal, because a horse's small stomach cannot handle a large starchy meal at once.
Water is the nutrient owners most often underestimate. A horse drinks roughly 5 to 10 liters per 100 kg of body weight each day — 25 to 50 liters for a 500 kg horse. This calculator uses 5 liters per 100 kg for an idle horse, rising to 10 liters per 100 kg for very heavy work, and adds 25 percent in hot weather. Clean water should always be available, and in winter check that buckets and troughs have not frozen over.
These are starting points, not prescriptions. Age, breed, metabolism, body condition, and hay quality all shift the real requirement. Weigh your hay instead of guessing by the flake, watch your horse's body condition every two weeks, and adjust the ration in small steps.
Worked example
Take a 500 kg horse in moderate work — ridden three to five hours a week — fed on grass hay.
Step 1: Forage dry matter — moderate work uses 1.8 percent of body weight, so 500 × 0.018 = 9.0 kg of dry matter per day.
Step 2: Hay as fed — hay is about 90 percent dry matter, so 9.0 ÷ 0.90 = 10.0 kg of grass hay per day.
Step 3: Grain — moderate work uses 0.5 percent of body weight, so 500 × 0.005 = 2.5 kg of grain per day, split into two meals.
Step 4: Total feed — 10.0 kg of hay plus 2.5 kg of grain = 12.5 kg per day.
Step 5: Water — moderate work uses about 6.5 liters per 100 kg, so 500 × 0.065 = 32.5 liters, about 33 liters per day.
Enter 500 kg, moderate work, and grass hay above and you will get exactly these figures.
FAQ
How much hay should a horse eat per day?
A horse should eat forage equal to about 1.5 to 2 percent of its body weight per day, measured as dry matter. For a 500 kg horse that is 7.5 to 10 kg of hay dry matter, or roughly 8.3 to 11.1 kg of hay as fed, since hay is about 90 percent dry matter. Never drop forage below 1 percent of body weight in dry matter, even for an overweight horse — the gut needs constant fiber.
Does my horse need grain?
Not always. An idle horse or one in light work usually meets its energy needs from forage alone, and adding grain only risks weight gain and digestive upset. Grain becomes useful as work increases: a horse in moderate work typically needs grain equal to about 0.5 percent of body weight per day, rising to around 1 percent for very heavy work. Introduce grain gradually over one to two weeks, split it into at least two meals, and never feed more than about 0.5 percent of body weight in one meal.
How much water does a horse drink per day?
A horse drinks roughly 5 to 10 liters of water per 100 kg of body weight per day, so a 500 kg horse needs about 25 to 50 liters. The amount rises with workload, hot weather, and a dry hay diet, and falls when the horse eats a lot of fresh pasture, which is mostly water. Always provide clean water freely, and check in winter that buckets and troughs have not frozen over.
How much hay is in a bale, and how do I weigh it?
A small square bale usually weighs 18 to 25 kg (40 to 55 lb) and a large round bale 250 to 500 kg, but bales vary, so weighing is the only reliable method. Hang a luggage scale from the bale, or weigh yourself holding the hay on a bathroom scale and subtract your own weight. Feeding by flakes is guesswork: one flake can weigh anywhere from 1 to 3 kg depending on how tightly the bale was packed.
Can a horse live on pasture alone?
Yes, if the pasture is good quality and plentiful, many idle or lightly worked horses thrive on grass alone. Fresh pasture is only about 20 to 25 percent dry matter, so a 500 kg horse needs around 35 to 45 kg of fresh grass a day to get its 9 kg of dry matter, which means grazing most of the day. Pasture quality drops in winter and in drought, and lush spring grass can trigger laminitis in prone horses, so monitor body condition and add hay when the grass thins out.