How Much Water to Drink Before, During and After a Workout, Sip by Sip

You need less water before a workout than most people think, a steady sip during a long one, and a measured refill after it. The numbers on this page come from the 2017 position statement of the National Athletic Trainers' Association (NATA), written for active people of every level, with the 2007 stand of the American College of Sports Medicine beside it.

This is the hub of our Exercise and Heat guides. It gives you the plan for an ordinary training day, then sends you to the pages that go further: your own sweat rate, sports drinks, creatine, running, heat and cold.

How Much Water Should You Drink Around a Workout?

Start the session well hydrated, drink to thirst if it lasts under an hour, and sip about 200 ml (7 oz) every 15 to 20 minutes if it runs longer. Afterwards, drink 1 to 1.5 L for every kilo you lost, and keep the loss across the session under 2 % of your body weight.

The American College of Sports Medicine (ACSM) drew the same line ten years earlier. Its abstract says the goal of drinking during exercise is to "prevent excessive (>2% body weight loss from water deficit) dehydration".

Should I Drink Extra Water Before a Workout?

No, not for an everyday session. NATA says recreational athletes "should not need to consume extra fluids before activity but should begin exercise euhydrated", which means you start with your normal body water. If you drank your usual amount today and your pee is light in colour, you are ready to train.

The Korey Stringer Institute at the University of Connecticut uses the same check before exercise: light-coloured urine. If you train first thing in the morning, a 250 ml (8 oz) glass on the way out covers the night without a drink.

A day of dark pee and little to drink is different. ACSM advises that drinking ahead, when you need it, "should be initiated when needed at least several hours before the activity", so a litre at the gym door comes too late. Drink through the afternoon instead.

When Should I Drink Water During Exercise?

Once a session runs past an hour, drink as you go: NATA says about 200 ml (7 oz) every 15 to 20 minutes "may be ideal". Under an hour, plain water to thirst is enough. Either way, aim to finish no more than 2 % lighter than you started, and never heavier.

Under an Hour

• Plain water
• Drink when thirsty
• No timer and no sports drink

Over an Hour

• About 200 ml every 15 to 20 minutes
• A timer helps once thirst lags
• A carbohydrate-electrolyte drink may help

Sessions Under an Hour

A 40-minute class or a 30-minute run needs nothing but water. NATA writes that people in "physical activity lasting less than 1 hour should require no substances other than water".

Take a bottle and drink when you want to. You do not need a timer.

Sessions Over an Hour

At 200 ml every 15 to 20 minutes you drink 600 to 800 ml (20 to 27 oz) an hour. The Korey Stringer Institute gives a slightly larger rule of thumb, 200 to 300 ml every 15 minutes, which comes to 800 ml to 1.2 L an hour.

Which one fits you depends on how much you sweat. NATA reports adult sweat rates during exercise from 0.5 to 4.0 L an hour, so one person's right amount is another person's overdose. Two weigh-ins tell you where you sit, and our guide on how to calculate your sweat rate walks through them with numbers.

Runners face one more limit: everything they drink, they carry. Our page on how much water runners should drink covers bottles, routes and race days.

How Much Water Should You Drink When Lifting Weights?

No source we read gives a separate number for lifting, so the general rules apply. Drink water to thirst in a session under an hour, about 200 ml every 15 to 20 minutes beyond that, and weigh yourself before and after if you sweat heavily. A 500 ml (17 oz) bottle at your bench makes an easy marker: if it is empty before your last set and you are still thirsty, refill it.

If you take creatine, the plan stays the same. The supplement has no water amount of its own, as our page on water with creatine explains.

Drinking to Thirst or on a Timer

NATA notes that thirst normally rises as you near a 2 % water loss, but during exercise that signal can be "absent or ignored". It also says that "drinking to thirst during activity most likely represents a safe strategy to prevent overdrinking".

So use both. In short sessions, drink when thirsty; in long ones, set a timer every 15 to 20 minutes and let thirst decide between a sip and a full mouthful.

How Much Should I Drink After Exercise?

Weigh yourself before and after, then drink back more than the scale says you lost:

100–150 %

of the weight you lost

1–1.5 L

per kg lost (15 to 23 oz per lb)

2 h

to drink it back in

NATA places the top of that range on days when your next session is less than 4 hours away. The 2-hour window comes from the Korey Stringer Institute.

You drink more than you lost because part of the refill leaves as urine. The Korey Stringer Institute notes that water without the sodium you sweated out makes your body produce extra urine, so you stay short. Salt in your food or drink holds more of it in.

Meals help. NATA writes that "the electrolyte and water contents of meals contribute to fluid replacement and can enhance fluid retention", so a glass of water with dinner does more than the same glass on an empty stomach.

How Do Heat and Cold Change the Plan?

Heat raises how much you need, and cold hides the need. For work in the heat, NIOSH advises 1 cup (8 oz) of water every 15 to 20 minutes for moderate activity under 2 hours, and says intake "should not exceed 6 cups per hour" (48 oz, about 1.4 L).

Our page on how much water to drink in hot weather turns those numbers into a plan for summer training and outdoor work. In cold weather NATA reports that "the drive for thirst is blunted" and that cold "induces a slight diuretic effect", so you can run short without feeling thirsty; see dehydration in cold weather.

• Hot day: chill your water. NATA says people exercising in the heat drink more of their own accord when the fluid is cold.
• Cold day: set a timer, because thirst shows up late.
• Either day: weigh in before and after, the same as always.

Do You Need a Sports Drink or Electrolytes?

Not for a session under an hour. For longer sessions or hard intervals, NATA says athletes "may benefit" from drinks with carbohydrate and electrolytes, and NIOSH advises sports drinks with balanced electrolytes when sweating lasts several hours.

Who needs them, who is fine with water, and what the label should show are covered on our page on electrolytes and sports drinks.

Can You Drink Too Much During Exercise?

Yes. Drinking far more than you sweat lowers the sodium in your blood, a condition called exercise-associated hyponatremia. NATA says it comes from "excessive consumption of hypotonic fluids (including sports drinks)", and that it shows up more often in women and after activity longer than 4 hours.

The scale is your guard: if you weigh more after a session than before, you drank more than you sweated. Healthy kidneys clear at most about 0.7 to 1.0 L of water an hour, according to the US National Academies, and hours of drinking past your sweat loss outrun them.

The symptoms and the full risk picture sit on our page on whether you can drink too much water. The opposite problem, running short, has its own page of signs of dehydration.

Your Daily Goal on Training Days

Your daily goal and your workout refill are two separate numbers. Glubbo's habit formula sets a daily drinks goal from your weight, activity, climate and sex, and its activity setting adds 100 ml for Moderate and 300 ml for High: far less than a hard hour of sweat.

So on training days, keep your daily goal and add back what the scale says you lost. Here is how that looks for three people, with the same formula as the water intake calculator.

Ben's day comes to 4.45 to 5.1 L of drinks. He spreads it out, because the NIOSH ceiling of 6 cups an hour applies to him too.

These examples are for healthy adults; the formula is never for children or pregnancy. For where the everyday number comes from, read how much water you need in a day.

What to Do Today

1. Before your next session, pee, then weigh yourself in light, dry clothes.
2. Take one bottle you know the size of. Drink to thirst if the session is under an hour, about 200 ml every 15 to 20 minutes if it is longer.
3. Weigh yourself again before you drink anything after, and work out your loss.
4. Drink back 1 to 1.5 L per kg lost over the next two hours, with a meal if you can.

To spread your everyday goal around your training hours, build a plan with the water drinking schedule. It puts your first glass at waking and your last an hour before bed.