Sweat Rate Calculator

This calculator uses a standard pre/post weigh-in protocol to estimate your sweat rate during training. The formula accounts for body weight change and fluid intake over the duration of your session.

Sweat rate varies with temperature, humidity, exercise intensity, acclimatisation, and individual physiology. A single measurement provides a baseline, not a universal constant. For a more complete picture, repeat the measurement under different conditions.

For a detailed guide on measuring your sweat rate manually, read our article: How to Measure Your Sweat Rate (and Why Guessing Fails)

Fluid is only half of it. Sweat carries sodium, and most athletes lose far more than a standard sports drink replaces, so it is worth reading how much sodium you actually need alongside why osmolality matters for performance before you choose a drink concentration.

To turn your sweat rate into an hour-by-hour intake plan, run the numbers through the Fuelling Strategy Engine or set a target time with the race calculator. Event-specific execution is covered in our marathon fuelling plan, Ironman nutrition plan and HYROX fuelling guide.

Once you know your losses, match them to a product. One serve of HYDRAX CORE delivers 980mg of sodium with a 2:1 dual-carb system, HYDRAX PRIMER pre-loads sodium before you start, and single-serve sachets make race-day dosing simple. You can build your kit here.