Hiking Water Calculator
Estimate how much water to carry based on how long you are walking, how hard, how hot it is and how reliably you can refill. The method and every assumption behind the number are shown with the result.
Your estimate appears here
Enter your hike details and select Calculate. You will see the figure per person, the group total, a suggested reserve and how the number was worked out.
Water needs vary significantly by person, weather, exertion and trail conditions. Use this result as a planning estimate and always check local conditions.
Reading the result well
It is a planning figure
The estimate covers a typical adult on a typical day. Individual sweat rates vary by a factor of two or more, so treat it as a starting point and adjust from your own experience.
Drink before you start
Arriving well hydrated reduces what you need on the trail. Sipping steadily works better than large amounts at long intervals.
Heat and salt go together
On long hot days, water alone can leave you low on electrolytes. Salty snacks or an electrolyte mix belong in the pack alongside the bottles.
Refills need a backup
Streams dry up and taps get turned off. If your plan depends on refilling, carry a filter or treatment and enough water to reach an alternative source.