How Much Water to Drink Before, During and After a Workout
There's no single number — but there is a method. The American College of Sports Medicine's guidance comes down to three moves: start the session hydrated, don't lose more than about 2% of your body weight while you train, and replace what you lost afterwards. Here's each one in bottles.
How much water should you drink before a workout?
About four hours before you train, slowly drink 5–7 mL of fluid per kilogram of body weight. If you haven't urinated by two hours out, or it's dark, have a little more. In ounces:
| Body weight | About 4 hours before | 2% of body weight |
|---|---|---|
| 120 lb | 9–13 fl oz | 2.4 lb |
| 150 lb | 12–16 fl oz | 3.0 lb |
| 180 lb | 14–19 fl oz | 3.6 lb |
| 210 lb | 16–23 fl oz | 4.2 lb |
| 240 lb | 18–26 fl oz | 4.8 lb |
For most people that's one 16.9 fl oz bottle (500 mL), give or take. Drinking it with a meal helps you hold on to it.
How much should you drink during a workout?
Sweat rates vary enormously — from under half a litre to more than two litres an hour, depending on the person, the heat and the effort. So the useful number is yours, and the bathroom scale finds it:
- Weigh yourself, without clothes, right before a typical session.
- Train for an hour, keeping track of what you drink.
- Towel off and weigh yourself again.
- Each pound lost is about 16 fl oz of sweat. Add back what you drank: that's your hourly sweat rate.
Aim to drink enough during long sessions to keep the loss under about 2% of body weight (the right-hand column above) — not to replace every ounce. Most people's workouts under an hour don't need much more than sips.
How much water should you drink after a workout?
For every pound you're down after training, drink about 23 fl oz — a bit under one and a half 16.9 fl oz bottles — over the next few hours. Food helps: a meal brings the sodium that lets your body keep the water.
Can you drink too much water when you exercise?
More is not better. Over a long event, drinking far beyond what you sweat can dilute the sodium in your blood — hyponatremia — which can be serious. If you weigh more after a session than before, you drank more than you needed. Heavy, salty sweaters and anyone training for hours should read up on electrolytes.
This is general guidance for healthy adults. If you have a heart or kidney condition, or have been told to limit fluids, follow your doctor's numbers instead.
Sources
- American College of Sports Medicine. Exercise and Fluid Replacement (position stand), 2007.
- National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate, 2005.
Questions people ask
How much water should I drink before a workout?
The American College of Sports Medicine suggests about 5–7 mL per kilogram of body weight, slowly, around four hours before — roughly one 16.9 oz bottle for a 150 lb person. If you aren't urinating or it's dark, a little more about two hours before.
How much should I drink after a workout?
About 1.5 litres for every kilogram lost — roughly 23 fl oz for every pound the scale dropped — spread over the next few hours, with a meal.
Can you drink too much water while exercising?
Yes. Drinking far more than you sweat during a long event can dilute the sodium in your blood (hyponatremia), which can be dangerous. Gaining weight during exercise is the sign you drank more than you lost.
Do I need a sports drink?
For most sessions under an hour, water and your next meal cover it. For long or very sweaty sessions, drinks with sodium and carbohydrate can help — see our electrolytes explainer.