Free Tool
Hiking Water Calculator
Find out exactly how much water to carry based on your body weight, hike duration, intensity, temperature, and altitude.
Water You Need
Dehydration tip: Thirst is a late signal — drink before you feel thirsty. Aim to drink 0.5 cups every 15–20 minutes on the trail.
Altitude note: Above 8,000 ft you lose more water through breathing due to low humidity and exertion. Increase intake even if you don't feel thirsty.
Heat note: In very hot conditions, electrolytes matter as much as water. Plain water alone can cause hyponatremia (low sodium) if you drink large amounts without electrolytes.
Frequently Asked Questions
How much water should I drink while hiking?
A general guideline is 0.5 liters (about 17 oz) per hour on moderate trails in comfortable weather. On strenuous hikes in hot weather, consumption can reach 1 liter per hour or more. The key is to drink before you feel thirsty — thirst is a late indicator of dehydration. Aim for about half a cup every 15–20 minutes while moving.
How much water does a day hike require?
A typical 6-hour moderate day hike requires roughly 3 liters (100 oz) of water for an average-sized person in comfortable weather. Strenuous hikes in heat can require 5–6 liters. Always carry slightly more than your calculated need — water sources can be dry, or a hike can take longer than planned.
Does altitude increase how much water I need hiking?
Yes. At high altitude (above 8,000 feet), your body loses more water through increased respiration due to low air pressure and humidity. Many hikers at altitude feel less thirsty than they should — a dangerous combination. Add at least an extra 0.5 liters per day for every 3,000 feet above sea level, and set reminders to drink.
Should I filter water or carry it all from the trailhead?
For hikes under 2–3 hours, carry all your water from the trailhead. For longer hikes with reliable water sources, use a filter or purification tablets to resupply on trail. Never rely on a single water source — always check recent trail reports for water availability, especially in late summer and drought conditions. A lightweight filter like the Sawyer Squeeze adds only 3 oz and eliminates the need to carry all your water.
What are the signs of dehydration while hiking?
Early signs include dark yellow urine, headache, fatigue, and reduced pace. Moderate dehydration brings dizziness, nausea, and muscle cramps. Severe dehydration causes confusion, rapid heartbeat, and inability to continue hiking — a genuine emergency in the backcountry. Check urine color frequently: pale yellow is good, dark amber means drink immediately. Clear urine can indicate overhydration without electrolytes.