How much to drink before, during and after exercise

2026-10-30

Start your workout already hydrated, drink only if the session lasts longer than about an hour, and afterwards replace what you actually lost. In numbers: about 5–10 ml per kg of body weight in the 2–4 hours before exercise, roughly 0.4–0.8 liters (14–27 fl oz) per hour during long sessions (guided by thirst), and about 1.5 liters for every kilogram you lost if you need to recover quickly. Those figures come from the American College of Sports Medicine (ACSM) position stand and the German Nutrition Society's 2020 position on fluid replacement in sports. Here is how to turn them into a plan.

Why the amount matters (in both directions)

When you exercise, most of the energy you burn turns into heat, and sweating is how you get rid of it. Sweat rates vary enormously: from about 0.3 to 2.5 liters per hour depending on the person, the intensity and the weather.

Too little fluid is a problem. Losing 2–4% of your body mass as sweat is associated with lower endurance, strength and concentration, and the effect is bigger in the heat. That is why the ACSM's goal is to avoid losing more than 2% of body weight during exercise. For a 70 kg person that is 1.4 kg; for a 150 lb person, 3 lb.

Too much fluid is also a problem. Drinking far more than you sweat out, especially plain water over many hours, can dilute the sodium in your blood (exercise-associated hyponatremia). It is rare, but it can be dangerous, and it mostly affects slower participants in long events who drink at every opportunity. We cover it in detail in can you drink too much water?.

So the aim is not to "drink as much as possible". It is to land somewhere between those two extremes.

Before exercise: start hydrated, don't tank up

If you've been drinking normally through the day, you are probably already fine. For important or long sessions, the guidance is:

2–4 hours before: about 5–10 ml per kg of body weight. That is roughly 350–700 ml (12–24 fl oz) for a 70 kg (155 lb) person.
Check your urine: light yellow is the goal. If it is still dark, have a little more. See what your urine color says.
Don't overdo it: drinking large amounts right before you start mostly sends you to the toilet and, in extreme cases, lowers blood sodium before you've even begun.

Drinking a few hours ahead, rather than in the last ten minutes, gives your kidneys time to get rid of any excess.

During exercise: depends on how long and how hot

Under about an hour

For most workouts under 60 minutes (a gym session, a 5K, a spin class), you don't need to drink during the session if you started well hydrated. Sip if you are thirsty or it is hot; otherwise, drink afterwards.

One to several hours

Here drinking starts to matter. The ACSM range of about 0.4–0.8 liters per hour is a sensible frame. In practice:

Small, regular sips work better than drinking a lot at once.
Thirst is a reliable guide for most people. An international consensus panel on exercise-associated hyponatremia (Hew-Butler et al., 2015) concluded that drinking when thirsty is the safest individual strategy for most athletes.
A useful ceiling: the German position paper suggests covering no more than about 80% of your sweat loss during longer exercise. You should finish slightly lighter than you started, never heavier.

If you want to know your own numbers instead of guessing, measure your sweat rate. It takes one weighing before and one after.

When water isn't enough

Water is the right drink for most sessions. Sodium and carbohydrates start to help when:

you sweat heavily (more than about 1.2 liters per hour) and the activity lasts more than about 2 hours: add sodium;
the effort lasts more than about 90 minutes or is a long match: about 30–60 g of carbohydrate per hour helps performance.

Whether that comes from a sports drink, a gel with water or food is up to you; see sports drinks vs water and electrolytes: when you actually need them.

After exercise: replace what you lost

The simplest measure is the scale. Every kilogram of weight lost during a session is about one liter of fluid (a pound is about 15 fl oz).

If you have time (no hard training in the next day and you lost less than about 5% of your body mass), normal meals, snacks and water will rehydrate you. Food contains both water and the salt you sweated out.
If you need to recover fast (two sessions in a day, a tournament), aim for about 1.5 liters of fluid per kilogram lost (about 23 fl oz per pound), spread over the next few hours. The extra 50% covers the urine you'll produce along the way.
Drink it in portions rather than all at once, and pair it with a meal or a salty snack. Sodium helps your body hold on to the water instead of passing it straight through.

Example: you weigh 72.0 kg (158.7 lb) before a two-hour bike ride and 71.0 kg (156.5 lb) after. To recover quickly for tomorrow, that is about 1.5 liters (50 fl oz) over the evening, on top of what you drink anyway with dinner.

A simple plan for common sessions

30–60 minutes, mild weather: drink normally during the day, a glass in the hours before, drink to thirst afterwards.
60–90 minutes or hot weather: 350–700 ml in the 2–4 hours before, sip to thirst during (roughly 0.4–0.8 l/h), weigh yourself before and after a few times to learn your pattern.
Over 2 hours: the above plus a drink or food with sodium and carbohydrates, and a plan you've tested in training. For running specifically, see hydration for runners.
Two sessions in one day: weigh before and after the first, replace about 1.5 l per kg lost with food and some salt before the second.

Don't forget the rest of the day

Exercise needs sit on top of your normal daily intake. If you train most days, your baseline is a bit higher than a sedentary person's. Water Tracker's suggested goal accounts for this: it starts from about 33 ml per kg of body weight and adds 500 ml if you mark yourself as active. You can log the bottle you drank at the gym from your iPhone or straight from your Apple Watch, and each drink can be saved to Apple Health.

The bottom line

Start hydrated: 5–10 ml/kg in the 2–4 hours before, aiming for light yellow urine.
Under an hour, you usually don't need to drink during exercise.
Longer sessions: sip to thirst, roughly 0.4–0.8 l per hour, and finish slightly lighter, not heavier.
Add sodium and carbohydrates for long, sweaty efforts.
Afterwards, food and water are enough most of the time; if you need to recover fast, drink about 1.5 l per kg lost.

This article is general information, not medical advice. If you have a health condition, are pregnant or take medication, ask your doctor how much you should drink.