How much water to drink when exercising depends on how long you train, how hot it is and how much you sweat. There is no single number that suits everyone, but there is a simple plan that works for most of the people we train at our Samford gym, from first-time walkers to marathon runners.
Why one number does not fit everyone
Two people doing the same session can lose very different amounts of fluid. Body size, fitness, clothing, the time of day and the weather all change how much you sweat.
A 45-minute strength session in an air-conditioned gym is a very different job from a 90-minute run along the D’Aguilar range in January. Your drinking should change with the session.
How much water to drink when exercising: the plan
| When | What to aim for | Notes |
|---|---|---|
| 2 to 3 hours before | About 400 to 600 mL | Gives you time to go to the toilet before you start |
| 10 to 20 minutes before | A few mouthfuls, 150 to 250 mL | Optional for short sessions |
| During, under 60 minutes | Sip to thirst | Most people need little more than this |
| During, over 60 minutes | Roughly 400 to 800 mL per hour | More in heat, less in cool weather |
| After | Around 1.25 to 1.5 L for each kilogram lost | Spread over the next few hours with a meal |
The weigh-in test
The easiest way to learn your own sweat rate is to weigh yourself before and after a typical session, in the same light clothing, after going to the toilet.
- Weigh yourself before training.
- Note how much you drink during the session.
- Weigh yourself again straight after.
- Every kilogram lost is about one litre of sweat, plus whatever you drank.
Do this a few times across the year, once in winter and once in summer. Most of our runners are surprised by the gap between the two.
Signs you have the balance wrong
Drinking too little shows up as dark urine, a dry mouth, feeling flat or dizzy, and a session that feels much harder than it should.
Drinking too much is less common but real, mostly in long events where people force down water well beyond thirst. If you finish a long run heavier than you started, you drank more than you needed.
Pale yellow urine through the day is a reasonable everyday guide for most people.
Plain water or something else?
For most sessions under an hour, plain water is all you need. For long or very hot sessions, many people also want some salt and carbohydrate. Our electrolyte drinks guide covers when that is worth it and when it is not.
Away from training, keep it simple: a glass with each meal and a bottle within reach. Some of our clients like to add a liquid trace mineral to one glass of water each day. If that is you, here is a plain guide to fulvic acid minerals, including what is in the bottle.
Food matters too. Fruit, vegetables, soups and milk all add fluid across the day. Our pre workout snack guide has ideas that sit well before a session.
A simple routine to start with
- Drink a glass of water when you wake up.
- Have a glass with every meal.
- Take a bottle to every session and sip when thirsty.
- For sessions over an hour, drink to a plan rather than to memory.
- Weigh in before and after a few times each season.
Common questions
Should I drink water during a 30-minute workout?
Sip if you are thirsty. Most people start a short session with enough fluid on board, especially if they had a glass in the couple of hours beforehand.
Is it bad to drink a lot of water before exercise?
A large amount right before you start can slosh around and send you to the toilet mid-session. Drink most of it two to three hours out, then just a few mouthfuls closer to the start.
Do I need more water as I get older?
Thirst can be a less reliable signal as we age, so routines matter more. Having water at set times, like meals and sessions, takes the guesswork out.
How do I know how much I sweat?
Weigh yourself before and after a typical session. Each kilogram lost is roughly one litre of sweat, plus anything you drank during the session.
When to get it checked
If you regularly feel dizzy, faint or unwell during or after training, stop and speak with your GP, then book in with an exercise physiologist so we can look at how your sessions are structured.