Electrolytes, Sodium and Water: Read the Drink Label

Updated 17 October 2026 · Reviewed by Tools by Layna Editorial Team · General information only

An electrolyte drink is not simply stronger water. The amount you drink determines fluid intake; its sodium and carbohydrate concentrations determine two other quantities. Keeping those tasks separate makes the label more useful than the word “hydration” on the front.

Three questions, three different units

Record fluid in millilitres or litres, sodium in milligrams, and carbohydrate in grams. A large bottle can deliver plenty of fluid but little sodium; a concentrated supplement can supply sodium without much carbohydrate. The AIS distinguishes electrolyte supplements from sports drinks, which combine fluid with fuel. Neither name tells you whether a product suits a particular session.

A 500 mL bottle worked example

Imagine a label listing 60 mg sodium and 6 g carbohydrate per 100 mL. Drinking 500 mL means multiplying both figures by five:

Those are hypothetical label values, not a recommended dose. If you drink only half the bottle, halve all three amounts. If a powder label gives values per prepared serving, check the required water volume before comparing it with another product.

Choose the purpose before the product

For a short session, first ask whether you need anything beyond ordinary drinks and meals. For prolonged exercise or unusually large losses, a sports dietitian can help consider fluid, fuel and sodium separately. The AIS notes uncertainty around optimal sodium-replacement plans; sweat volume alone does not reveal sweat-sodium concentration. Salt marks on clothing are not a laboratory measurement.

If fuel is already supplied by food, more carbohydrate in a drink may not serve the same purpose as an electrolyte-only product. Conversely, an electrolyte tablet does not automatically provide the carbohydrate intended in an endurance fuelling plan.

What the site calculators can check

The sodium calculator converts an entered sodium amount to an approximate salt equivalent. It does not decide how much sodium you lost. The water calculator uses a body-weight and activity heuristic; it does not analyse a drink or measure sweat. Use the label arithmetic above to describe intake, then keep assessment of need as a separate question.

Electrolytes do not make overdrinking harmless

Adding sodium does not remove the risk from drinking excessive fluid. The AIS identifies excessive intake as central to severe exercise-associated hyponatraemia. Avoid turning a calculator output into a compulsory drinking quota. Medical sodium restrictions, kidney conditions and vomiting or diarrhoea require advice suited to the situation.