📖 Overview
Use this calculator as a hydration planning baseline for active routines.
🧪 Example Scenarios
Use these default and higher-pressure example inputs to explore how sensitive this calculator is before using your real numbers.
| Input | Base Case | Higher Pressure Case |
|---|---|---|
| Body Weight (kg) | 75 | 86.25 |
| Active Minutes Per Day | 45 | 54 |
⚙️ How It Works
This estimates daily water needs from body weight and activity duration using a simple planning model.
The Formula
Daily Water (L) = Weight (kg) × 0.033 + Activity (min) × 0.012
| Weight | Body weight in kilograms |
| 0.033 | Baseline water factor: ~33 mL per kg of body weight |
| Activity | Active exercise minutes |
| 0.012 | Extra hydration per minute of activity (~12 mL/min) |
💡The old "8 glasses a day" rule is not based on modern evidence. Needs vary by body size, activity, climate, and diet. Use this estimate as a planning baseline.
Quick Reference
| Weight | Sedentary | 30 min exercise | 60 min exercise |
|---|---|---|---|
| 60 kg | 2.0 L | 2.4 L | 2.7 L |
| 70 kg | 2.3 L | 2.7 L | 3.1 L |
| 80 kg | 2.6 L | 3.0 L | 3.6 L |
| 90 kg | 3.0 L | 3.4 L | 4.1 L |
When To Use This
- Use this tool when you need a fast decision during active planning or execution.
- Use this before committing money, time, or tradeoffs that are hard to reverse.
- Use this to compare options using the same assumptions across scenarios.
Edge Cases To Watch
- Results can be misleading if key inputs are missing, stale, or unrealistic.
- Very small or very large values may amplify rounding effects and interpretation risk.
- If assumptions change mid-decision, recalculate before acting.
Practical Tips
💡 Increase intake in hot weather or high sweat sessions.
💡 Use urine color and thirst as practical feedback signals.
💡 Spread intake through the day for better consistency.
Frequently Asked Questions
❓ Is one target valid for everyone?
No, hydration needs vary by climate, diet, and health status.
❓ Should I include electrolytes?
For long or intense sessions, electrolyte planning may be useful.