Estimate how much water to bring for hiking, backpacking, camping, trail running, and outdoor trips. This calculator adjusts water needs based on trip time, distance, weather, effort, elevation gain, body weight, group size, water sources, and safety reserve.
Trip time:
Enter how many hours you expect to be active. Time is usually the biggest driver of water needs.
Conditions:
The calculator adjusts for heat, effort level, sun exposure, body weight, distance, and elevation gain.
Water sources:
If reliable water is available on the route, the calculator estimates a lower starting carry amount while still showing total trip water need.
A water needs calculator helps estimate hydration for hiking, backpacking, camping, trail running, hunting, fishing, and outdoor work. It can help balance safety with pack weight.
Water needs vary by person. Heat illness and dehydration can be serious, so use this as a planning estimate and carry extra when conditions are uncertain.
This calculator uses a practical outdoor hydration estimate:
Water Needed = hourly water need × activity time × condition factors + meal water + safety reserve
A common starting point is about 0.5 to 1 liter per hour of hiking, with more needed in heat, sun, altitude, steep terrain, or hard effort.
Water weighs about 2.2 pounds per liter, about 1 kilogram per liter, or about 8.34 pounds per gallon.
Yes, reliable water sources can reduce starting carry weight, but you should confirm they are flowing and bring a way to filter or treat the water.
Electrolytes can help on long, hot, or high-sweat hikes, especially when drinking a lot of water over many hours.