How much water do you really need?
Science‑backed, tailored to your hike — in seconds.
⏱️ Duration
2h
4h
6h
8h
8+
🌡️ Temperature
❄️ Cold (<50°F)
☀️ Moderate (50-80°F)
🔥 Hot (>80°F)
⛰️ Intensity
🚶 Easy / Flat
🏔️ Moderate / Hills
⛰️ Strenuous / Mountain
⚖️ Your weight (optional, for precision)
lbs
kg
better accuracy with weight
3.2 L
about 2 x 1.5L smartwater bottles
or 1.5 x 32oz Nalgene
💧 For a 4h moderate hike in 75°F, sip 0.5L every hour. Don’t forget electrolytes!
How is this calculated?
Base: 0.5L per hour (American Hiking Society).
Heat factor: +50% if hot, -10% if cold.
Effort factor: +40% if strenuous, -10% if easy.
Weight adj: +0.1L per 20 lb above 150 lb (or equivalent in kg).
*Always carry extra water for emergencies.