Electrolyte Calculator for Athletes — Sodium, Potassium & Magnesium

Why Electrolytes Matter During Exercise

Sweat isn't just water. Every litre of sweat contains 400–1,200mg of sodium, 100–400mg of potassium, and 5–15mg of magnesium. These minerals regulate muscle contraction, nerve signalling, and fluid balance. When they're not replaced, performance deteriorates — and muscle cramps, nausea, and in extreme cases, hyponatremia can result.

Sodium: The Critical Electrolyte

Sodium is lost in far greater quantities than any other electrolyte, and it plays the most critical role in hydration. Sodium: * Maintains plasma osmolality (blood concentration) * Stimulates thirst, encouraging appropriate drinking * Drives glucose transport into intestinal cells, improving carbohydrate absorption * Preserves plasma volume, reducing cardiovascular strain

Individual Sweat Sodium Varies Widely

"Salty sweaters" can lose up to 1,800mg of sodium per litre of sweat — nearly 4x more than a low-sodium sweater. If you regularly see white residue on your skin or kit after exercise, you're likely a high-sodium sweater and need to be especially diligent about electrolyte replacement.

Potassium & Magnesium

* Potassium is primarily an intracellular ion involved in muscle and nerve function. Deficiency contributes to weakness and cramping. * Magnesium is a cofactor in 600+ enzyme reactions, including ATP production. Losses during endurance exercise are modest but significant over long durations.

Electrolyte Sources During Exercise

| Source | Sodium | Potassium | Ease of use | | :--- | :--- | :--- | :--- | | Sports drink (500ml) | 200–500mg | 100–150mg | ✓✓✓ | | Salt tablet | 300–500mg | Varies | ✓✓ | | Energy gel (with electrolytes) | 50–200mg | 25–50mg | ✓✓✓ | | Banana | ~1mg | ~422mg | ✓ (bulky) |

Q: Can too many electrolytes be harmful? A: In healthy exercising athletes, the kidneys excrete excess electrolytes efficiently. The risk of over-supplementing electrolytes during exercise is very low compared to the risk of deficiency. Follow your thirst and sweat rate as guides.

Q: Do electrolytes prevent muscle cramps? A: Electrolyte deficiency is one cause of exercise-associated muscle cramps, but not the only one. Neural fatigue and neuromuscular dysfunction also contribute. Adequate sodium and potassium intake reduces cramp risk, but is not a guaranteed prevention.