Every session you train, you lose more than just water. Sweat carries essential electrolytes — sodium, potassium, magnesium and calcium — that your muscles and nervous system rely on to function properly. Even mild dehydration, as little as 2% of body weight, can measurably reduce endurance, slow reaction time and increase your risk of cramping.

Most athletes underestimate how much fluid and sodium they actually lose per session, especially in hot or high-intensity conditions. Understanding your personal sweat rate and electrolyte loss is the first step to replacing what you lose accurately, rather than guessing with plain water or generic sports drinks.

This sweat loss calculator uses your sport, session length, effort level and training conditions to estimate your fluid and electrolyte loss per session and per month, so you know exactly what your body needs to recover faster and perform at your best.