His weight in, and how much hay and water he needs a day out — then the whole season’s hay in bales, with the waste from storage and from the feeder counted, the way the University of Maryland’s extension works it out.
Hay per day
20 lb of hay a day
The season
Grain — only if hay alone does not hold his condition
These are the published starting points for an average, healthy adult horse. A growing horse, a broodmare, a hard keeper, a horse in heavy work or one with a medical condition needs a ration worked out for him — ask your vet or an equine nutritionist. Change a horse’s feed gradually, and weigh the hay rather than counting flakes: flakes vary from bale to bale.
Feeding guidelines checked 2026-09-25.
Quick answer: a horse needs about 2% of his body weight in hay a day, according to the University of Maryland’s extension. That is 20 lb for a 1,000 lb horse and 22 lb for an 1,100 lb one. The Merck Veterinary Manual puts his total feed at 2–2.5% of body weight as dry matter, at least half of it forage. Clemson’s extension sets a floor of 1% of body weight as forage dry matter. He will also drink about a gallon of water per 100 lb, 8 to 12 gallons a day. Grain comes only if hay alone does not hold his condition, and never more than 0.5% of his weight in one meal. Merck’s own warning box says 0.25%.
How to use it
Put in his weight. You get hay per day, the total-feed range, the forage floor and his water. Fill in the season below it — how many days you will be feeding hay, how many horses, what one of your bales weighs and what it costs — and you get the bales to buy. Storage and feeder waste are counted the way the University of Maryland’s extension counts them, using two University of Minnesota studies.
If you do not know his weight, measure him with a tape and the free horse weight calculator. Every number on this page starts from it.
Hay first
A horse’s gut is built to process forage slowly, all day. The published rules all start there. Maryland’s 2% is hay as fed, straight off the bale. Merck’s 2–2.5% counts all feed as dry matter, the part that is left without its water. Merck adds that ponies, warmbloods and draft breeds tend to need the lower end and Thoroughbreds the higher. Clemson’s 1% floor is the least forage a horse should get in a day to keep his digestion working and cut the risk of ulcers. The three are measured differently, so the page shows them side by side instead of converting one into another.
Weigh the hay. A “flake” is whatever came off that bale, and flakes vary a lot from bale to bale and from field to field.
Grain, if he needs it
Most horses doing light work hold their condition on good hay alone. If yours does not, grain can add calories, but in small meals. Clemson’s extension says to limit a grain meal to 0.5% of body weight and split the day’s grain into two or three meals. The Merck Veterinary Manual gives the same 0.5% in its text and says larger meals raise the risk of laminitis and digestive upset. It also says meals should be at least four hours apart. In its “Pearls & Pitfalls” box, the same manual says meals over 0.25% of body weight should not be offered. The calculator shows both limits in pounds for your horse.
How many bales for the winter
Maryland’s worked example is a 1,000 lb horse fed hay from December 1 to March 31. That is 121 days at 20 lb a day, or 2,420 lb. With 5% storage waste for bales kept inside and 5% more from a hayrack, it comes to 2,668 lb, or 67 bales of 40 lb. Hay stored outside loses 5–35% depending on the weather. The feeder matters as much as the barn. In the Minnesota studies a round bale with no feeder wasted 57%, and a restricted-access feeder 5–11%. The calculator does this arithmetic for your horses, your days and your bales.