How to Use the Hydration & Electrolyte Calculator
Sweat carries away more than just water — sodium and potassium go with it too. Drinking water alone without replacing electrolytes can lead to muscle cramps, dizziness, and in severe cases hyponatremia. This calculator takes your workout duration and usual sweat level, then estimates the fluid, sodium, and potassium you're losing so you know how much to replace.
Sweat rate varies a lot between individuals, and with exercise intensity and ambient temperature. This calculator applies an hourly fluid loss estimate based on your sweat level — roughly 13.5 oz (low), 24 oz (moderate), or 34 oz (high) per hour — then multiplies your total fluid loss by typical sweat sodium and potassium concentrations to estimate electrolyte replacement. For a more precise personal number, weigh yourself before and after a workout; each pound lost is roughly a pint of fluid.
For light workouts under an hour, water alone is often enough. But for longer or higher-intensity sessions, or exercising in hot conditions, adding an electrolyte drink or a pinch of salt is generally recommended. These figures are general guidance — if you have a kidney or cardiovascular condition, talk to a doctor before adjusting your intake.
Frequently Asked Questions
If you exercise for more than an hour or sweat heavily during high-intensity training, water alone may not replace the sodium lost in sweat, raising the risk of hyponatremia. In these cases, an electrolyte drink or added salt is recommended.
If your clothes are just lightly damp afterward, that's 'low.' If they're soaked through and sweat is visibly dripping, that's 'high.' For a precise number, weigh yourself before and after exercise — each pound lost is roughly a pint of fluid.