Gym Hydration Calculator
Plan what to drink before, during and after your gym session based on how long and hard you’ll train.
Build your workout plan
Tell us what you’re doing and how long you expect to be out. If you’ve measured your sweat rate, you can use that too.
Complete the workout details, then build a practical timeline.
Safety: these estimates are general guidance, not medical advice. Never drink beyond measured losses or to the point of weight gain. Excessive intake can contribute to hyponatraemia. People with kidney, heart or liver conditions, pregnancy, or medicines affecting fluid balance should follow personal clinical advice.
How the workout estimate works
If you enter a sweat rate, the calculator uses part of that loss to estimate what you might drink during your workout. If you don’t know your rate, it gives a rough range based on what you’re doing, your size and the conditions.
You’ll usually get a different result for an easy session in cool weather than for a long workout on a hot day. Try the plan in training and adjust if you’re thirsty, uncomfortable or need to change pace.
Keep the plan practical
Check what your bottle holds and where you can refill or take a break. Afterwards, make a note of what you drank and repeat your sweat test if the conditions or your workout change.
Heat safety also involves pace, shade, clothing, cooling and acclimatisation. More fluid cannot make an unsafe session safe.
Workout hydration questions
How much water should I drink while running?
Consider how long and hard you’ll run, the weather, your thirst and where you can get a drink. If you’ve measured your sweat rate on a similar run, use it as a starting point.
Should I drink during a 30-minute workout?
If you’ve been drinking normally, you may be comfortable waiting until after a short, easy workout in mild weather. Keep a drink handy if conditions or your needs are different.
How much should I drink before exercise?
The planner uses your weight to suggest an amount to spread across the two to four hours before exercise, if you need it. Avoid trying to catch up by drinking a lot at once.
How much water should I drink after exercise?
Think about how much you lost, what you drank during exercise, when you’ll eat and when you next plan to train. Replace larger losses gradually.
Can you drink too much water during exercise?
Yes. Drinking beyond losses can cause body-mass gain and contribute to exercise-associated hyponatraemia. Sodium products do not make excessive drinking safe.