Build hydration plans for hard sessions and heat. See sweat rate, sodium, and timing clearly. Use practical inputs, instant outputs, charts, and exports today.
| Body Weight | Duration | Temp | Humidity | Intensity | Sweat Rate | During Fluid | Sodium Loss |
|---|---|---|---|---|---|---|---|
| 75 kg | 90 min | 31 °C | 60% | High | 1.43 L/h | 1.20 L | 1716 mg |
| 62 kg | 45 min | 27 °C | 50% | Moderate | 0.92 L/h | 0.50 L | 621 mg |
| 84 kg | 120 min | 34 °C | 70% | Very High | 1.95 L/h | 1.60 L | 3120 mg |
These rows are illustrative examples. Real values vary with pace, airflow, sun, fitness, and personal sweat chemistry.
Estimated sweat rate = base value + weight adjustment + heat adjustment + humidity adjustment + duration adjustment + intensity factor + sun factor + clothing factor
If you enter a measured sweat rate, the calculator uses that value instead of the estimate.
Total sweat loss = sweat rate × workout duration in hours
During fluid target = lower of practical drink tolerance and a percentage of total sweat loss
Pre workout fluid = body weight × 5 to 7 mL/kg based on starting hydration
Post workout fluid = remaining fluid deficit × 1.25
Total sodium loss = total sweat loss × sweat sodium concentration
The score blends temperature, humidity, duration, intensity, sun exposure, acclimation, and starting hydration into a 0 to 100 heat risk scale.
It estimates hydration needs for exercise in warm or hot conditions. It helps plan fluid timing, sodium support, and recovery targets before, during, and after training sessions.
Yes. A measured sweat rate from pre and post session body mass usually gives more accurate fluid planning than a model estimate, especially for repeated events or race preparation.
High humidity reduces sweat evaporation. That means you may feel hotter even when sweating more, so the same workout can create a greater heat burden and fluid deficit.
Not always. Many athletes perform well while replacing only part of their losses during the session, then finishing recovery afterward. Drinking far beyond comfort can create stomach problems.
They are especially useful in long sessions, heavy sweating, repeated workouts in one day, salty sweaters, or hot environments where sodium losses become meaningful.
It estimates how much fluid deficit may remain by the end of the session. Larger losses can affect comfort, pace, and heat tolerance, especially when they pass about two percent.
Yes. The calculator is activity neutral. Adjust duration, intensity, and sun exposure to fit the session. A measured sweat rate improves accuracy for any sport.
No. It is an educational planning tool. People with kidney disease, heart conditions, heat illness history, or fluid restriction advice should follow a qualified clinician’s guidance.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.