How much water should a horse drink per day?
An adult 500 kg horse at rest needs at least about 25 litres of water a day.
Exactly how much depends on feed, weather, work and the drinker.
We explain how to calculate it and how to tell if your horse is drinking too little.
- The minimum is about 5 litres for every 100 kg of body weight a day, or about 25 litres for a 500 kg horse.
- On dry hay alone, in hot weather, when working and in lactating mares, a horse needs much more, even two to three times as much.
- The drinker matters too: horses drank less from a slow-filling automatic drinker than from a bucket.
- The skin pinch test is not reliable. It is better to watch several things at once: drinking, urine, droppings and appetite.
Water is the cheapest part of a horse's diet and, at the same time, the one we think about least. We usually know how much hay and feed our horse gets, but rarely how much it drinks.
Below are the figures, the factors that change them, and simple ways to check this in your own horse.
How much water a horse needs
The Merck Veterinary Manual gives the minimum for an adult horse at rest in a moderate temperature: about 5 litres for every 100 kg of body weight a day[1]. For a 500 kg horse, that is about 25 litres. A horse fed a mixed ration of hay and concentrates usually drinks between 21 and 29 litres[1].
That, however, is the lower limit. In many everyday situations, a horse needs considerably more.
| Situation | Water per day | What to watch out for |
|---|---|---|
| At rest, moderate temperature | About 5 l per 100 kg of body weight, i.e. about 25 l at 500 kg[1] | Clean water available at all times |
| Mixed ration of hay and concentrates | Usually 21-29 l at 500 kg[1] | Check the drinker daily |
| Dry hay only | Up to almost twice as much[1] | Water always close to the hay |
| An hour of work in hot weather | Over 72 l to replace losses[1] | Water and a salt lick after work |
| Lactating mare | 12-14 l per 100 kg of body weight[1] | Frequent topping up, several water sources |
of water for every 100 kg of body weight is the daily minimum for an adult horse at rest. Sweating and lactation increase requirements by 50 to 200%[1].Merck Veterinary Manual, 2026
What changes how much water a horse drinks
Feed
On dry hay alone, a horse drinks almost twice as much as on a mixed ration[1]. And a horse that stops eating drinks less, because water requirements depend on the amount of feed eaten[2].
Pasture and stable
When horses moved from pasture to a stable, they drank more than twice as much water (from 2.4 to 6.4 litres per 100 kg of body weight), and their droppings were drier. In the first days after the change, gut motility also slowed down[3].
Heat, work, lactation
Sweating and lactation increase water requirements by 50 to 200%. After an hour of work in hot weather, a horse may need more than 72 litres to replace its losses[1].
Drinker
Horses drank less from an automatic drinker filling at 3 litres per minute than from a faster drinker (8 l/min) or a bucket. They drank most readily from a bucket[4].
Water temperature
In winter, ponies drank more when given warm water instead of near-freezing water[5]. In summer, chilled water did not change how much they drank[6].
Salt
In a study, the amount of salt a horse took from a salt lick of its own accord affected how much it drank[7]. That is why it is worth having a salt lick available at all times.
In a Danish study of 201 horses, a lack of water in the paddock was one of the factors that increased the risk of gastric ulcers[8]. Water should be available wherever the horse spends time, including turnout.
How to check if your horse is drinking enough
- Measure drinking for a few daysIf your horse drinks from buckets, write down how many buckets it drinks a day. With an automatic drinker, you can fit a water meter or offer water in buckets for a few days.
- Check the drinkerCleanliness every day, and flow rate once a week: how long the bowl takes to fill. A slow drinker means less water drunk[4].
- Don't rely on the skin pinch test aloneIn a study of working horses, skin tent duration was not related either to a blood measure of dehydration or to the amount of water drunk[9].
- Look at several things at onceHow much the horse drinks, urine colour, how moist the droppings are, and appetite. A horse that eats less usually drinks less too[2].
- Be careful with changesA change of feed and a change in housing are the changes best documented by research as raising the risk of colic[10]. Watch drinking and droppings more closely in the first days after such a change.
When to call the vet
- the horse is drinking clearly less all day, with no change in weather or work,
- the droppings are unusually dry and small, or the horse has stopped passing them,
- the horse is restless, looks round at its belly, paws or rolls,
- the horse has been drinking clearly more than usual for several days, with no obvious cause.
Frequently asked questions
How much water does a 500 kg horse drink?
The minimum at rest is about 25 litres a day. On a mixed ration of hay and concentrates, a horse usually drinks 21-29 litres, and on dry hay alone up to almost twice as much[1].
Should water be warmed in winter?
It's worth making sure it isn't ice-cold. In winter, ponies drank more when the water was warm than when it was near freezing[5]. Most importantly, the water should not freeze and should be available at all times.
Is an automatic drinker enough?
Yes, if it is clean and fills quickly enough. In a study, horses drank less from a slow-filling drinker than from a faster drinker or a bucket[4].
How can I tell if my horse is dehydrated?
One sign is not enough, and the skin pinch test proved unreliable[9]. Look at several things at once: how much the horse drinks, what its urine and droppings are like, and whether it is eating. If in doubt, the vet will assess hydration with a blood test.
Scientific sources
We checked every publication in the Crossref and PubMed databases. The numbers in the text link to the list, and the DOI links lead to the original articles.
- Liburt NR. Nutritional Requirements of Horses and Other Equids. Merck Veterinary Manual. 2026. www.merckvetmanual.com/management-and-nutrition/nutrition-horses/nutritional-requirements-of-horses-and-other-equids
- Freeman DE. Effect of Feed Intake on Water Consumption in Horses: Relevance to Maintenance Fluid Therapy. Frontiers in Veterinary Science. 2021;8:626081. doi.org/10.3389/fvets.2021.626081
- Williams S, Horner J, Orton E, Green M, McMullen S, Mobasheri A et al. Water intake, faecal output and intestinal motility in horses moved from pasture to a stabled management regime with controlled exercise. Equine Veterinary Journal. 2014;47(1):96-100. doi.org/10.1111/evj.12238
- Nyman S, Dahlborn K. Effect of water supply method and flow rate on drinking behavior and fluid balance in horses. Physiology & Behavior. 2001;73(1-2):1-8. doi.org/10.1016/s0031-9384(00)00432-7
- Kristula MA, McDonnell SM. Drinking water temperature affects consumption of water during cold weather in ponies. Applied Animal Behaviour Science. 1994;41(3-4):155-160. doi.org/10.1016/0168-1591(94)90020-5
- McDonnell SM, Kristula MA. No effect of drinking water temperature (ambient vs. chilled) on consumption of water during hot summer weather in ponies. Applied Animal Behaviour Science. 1996;49(2):159-163. doi.org/10.1016/0168-1591(96)01041-6
- Jansson A, Dahlborn K. Effects of feeding frequency and voluntary salt intake on fluid and electrolyte regulation in athletic horses. Journal of Applied Physiology. 1999;86(5):1610-1616. doi.org/10.1152/jappl.1999.86.5.1610
- Luthersson N, Nielsen KH, Harris P, Parkin TDH. Risk factors associated with equine gastric ulceration syndrome (EGUS) in 201 horses in Denmark. Equine Veterinary Journal. 2009;41(7):625-630. doi.org/10.2746/042516409x441929
- Pritchard JC, Burn CC, Barr ARS, Whay HR. Validity of indicators of dehydration in working horses: A longitudinal study of changes in skin tent duration, mucous membrane dryness and drinking behaviour. Equine Veterinary Journal. 2008;40(6):558-564. doi.org/10.2746/042516408x297462
- Curtis L, Burford JH, England GCW, Freeman SL. Risk factors for acute abdominal pain (colic) in the adult horse: A scoping review of risk factors, and a systematic review of the effect of management-related changes. PLOS ONE. 2019;14(7):e0219307. doi.org/10.1371/journal.pone.0219307
Published . This article is for educational purposes and does not replace an examination by a vet.
