📖 Overview
Use this calculator as a hydration baseline when training in warm conditions.
⚙️ How It Works
This estimates daily hydration from body weight, activity duration, and ambient temperature adjustment.
The Formula
Water (L) = (Weight × 0.033 + Activity × 0.012) × Temp Multiplier
| Base Need | 33 mL per kg of body weight |
| Activity Add | 12 mL per minute of exercise |
| Temp Multiplier | 1.0 at 20°C, 1.1 at 25°C, 1.2 at 30°C, 1.35 at 35°C+ |
💡In hot weather (30°C+) your fluid needs can increase by 20–35%. Pale yellow urine is a reliable real-time indicator of adequate hydration.
Quick Reference
| Temp | Multiplier | 70 kg / no activity | 70 kg / 60 min activity |
|---|---|---|---|
| < 20°C | ×1.00 | 2.3 L | 3.1 L |
| 25°C | ×1.10 | 2.5 L | 3.4 L |
| 30°C | ×1.20 | 2.8 L | 3.7 L |
| 35°C+ | ×1.35 | 3.1 L | 4.2 L |
Practical Tips
💡 Increase fluids in hot conditions.
💡 Use this as baseline and adjust by personal response.
Frequently Asked Questions
❓ Is this a medical prescription?
No, it is a planning estimate only.
❓ Should electrolytes be included?
For long or intense sessions, electrolyte planning may be useful.