Hydration Calculator

Staying hydrated during workouts matters because even small fluid losses have outsized effects on performance. Losing just 1–2% of your body weight in fluid — as little as two pounds for a 200-pound person, easily lost given sweat rates of 1–5+ pounds per hour — can cut exercise capacity by around 10%, make the same effort feel significantly harder, and progressively degrade skill and accuracy.

You also can't rely on thirst to guide you, since people tend to drink only about half of what they need during exercise. And because gastric emptying limits how much fluid you can absorb mid-session, the goal is to drink at a planned rate — roughly body weight in pounds ÷ 30 in ounces every 15 minutes — rather than waiting until you feel like it.

It's also important to replace sweat rather than plain water, meaning fluid with sodium, chloride, potassium, and some carbohydrate; two good options are LMNT and Momentous Fuel, both sponsors of the podcast. Water is the most important thing, but if you've lost a lot of it, you also need to add back electrolytes.

In short, managing hydration during a workout is the difference between performing at your peak and quietly losing a meaningful chunk of your capacity without even feeling it.

Use this calculator to determine how much fluid you need every 15–20 minutes of exercise.