Hiking Water Calculator
Built on standard sweat-rate ranges for hiking (0.4-1.0+ L/h): pick your pace and conditions and the calculator gives liters per hour and the total to carry or plan refills for.
Result
- Drinking rate
- 0.8 L/h
About 3.4 US cups or 27.1 fl oz per hour.
Beyond 2 hours or 1 L/h, replace sodium too - plain water alone can dilute blood sodium on long efforts.
How the calculation works
The model starts from standard hiking sweat-rate ranges - 0.5, 0.7 and 0.9 L/h for easy, moderate and hard effort at 20 °C - then adjusts:
- Below 10 °C the base drops 0.1 L/h; above 20 °C it climbs 0.02 L/h per degree, capped at +0.5.
- Humidity above 60% adds 0.1 L/h, above 80% adds 0.2 L/h.
- The total multiplies by your hours on trail; the cups figure converts liters at 236.6 ml per US cup.
The planning logic - carry versus refill strategy, electrolytes and the thirst debate - is in the hiking water guide. Calories and fluids move together: the hiking calorie calculator uses the same effort and terrain inputs.
Planning estimate only - not safety advice.
Frequently asked questions
Is the "one liter per two hours" rule any good?
As a middle-case shortcut, yes: it matches the calculator's moderate output around 20 °C. But sweat rate swings from about 0.3 L/h in cold, easy terrain to over 1.5 L/h in heat with climbing, which is why the calculator adjusts for temperature, humidity and effort instead of using a flat rule.
How does humidity change things?
Dry air evaporates sweat efficiently, so you cool well but quietly lose fluid. Above roughly 60% humidity evaporation slows and you both sweat more and cool worse; above 80% the calculator adds a full 0.2 L/h. High heat plus high humidity is the combination that produces heat illness.
Should I drink to thirst or on a schedule?
For most day hiking, drinking to thirst with regular check-ins is safe and sufficient. Scheduled overdrinking in long events can cause hyponatremia - drinking far more than you sweat is its own risk. Use the total as a planning number for carry and refills, not a quota to force.
What about electrolytes?
Beyond a few hours of heavy sweating, plain water alone dilutes sodium. Salty snacks cover most cases; electrolyte tablets or drink mixes make sense on hot, long days. The calculator's guidance scales with the duration and rate it computed.
Do I need to treat stream water?
Yes. Clear moving water can still carry Giardia and other pathogens. Filter, boil or chemically treat every natural source - the <a href="/boiling-point-altitude-calculator/">boiling point calculator</a> shows how boil temperatures and times shift at altitude.