Hike Water Needs Calculator
Calculate water needs for your hike by temperature, intensity, and body weight. Plan for hourly intake and total trip volume.
Quick Answer
Standard hiking water need: 0.5 liters (17 oz) per hour at 70°F moderate effort. Doubles in 90°F+ heat. Heavier people and high-intensity hikers need more. A 6-hour hike for a 160 lb person at moderate temps needs about 3 liters total.
Practical tips
- Drink 4-8 oz every 20-30 minutes — small sips beat big chugs
- Add electrolytes for hikes over 4 hours, hot weather, or strenuous effort
- Map water sources before you go and carry only what you need between resupplies
- Don't wait until you're thirsty — by then you're already mildly dehydrated
About This Tool
The Hike Water Needs Calculator estimates how much water to bring or drink based on body weight, ambient temperature, hike intensity, and duration. The result is hourly intake and total trip volume in liters and ounces. The calculation factors heat (the biggest variable), effort level, and body size — all of which significantly influence sweat rate and water loss.
The 0.5 Liter Per Hour Baseline
For a 70 kg (155 lb) person hiking moderate trail at 70°F, the standard water intake is 0.5 liters (17 oz) per hour. This is the calibration point for most hiking water guides. From this baseline, you scale up for heat (up to 2x at 100°F+), intensity (up to 1.8x at race effort), and body weight (linear scaling — a 100 kg person needs ~40% more than a 70 kg person at the same conditions). The math compounds: a 200 lb hiker at strenuous effort in 95°F heat might need 1.5+ liters per hour.
Heat Is the Dominant Variable
Sweat rate doubles between 70°F and 90°F, then doubles again between 90°F and 105°F. Desert hiking in summer (Grand Canyon below the rim, Mojave, Death Valley) routinely demands 1-2 liters per hour. The Grand Canyon Park Service recommends 1 gallon (3.8L) of water plus 1 quart (1L) of electrolyte drink per person for a single rim-to-river-and-back hike. Heat kills hikers every year in these environments — water planning is a survival skill.
Intensity Multiplies Need
Easy strolls burn less water than hard hiking. Strenuous effort (steep ascents, fast pace, heavy pack) increases sweat rate by 40-80%. Trail running and alpine climbing can require 1+ liter per hour even at cool temperatures because of the breathing and metabolic load. Your perceived effort is a reliable guide — if you're working hard, you're losing more water than you think.
Body Weight Scales Linearly
Larger people sweat more in absolute terms because they generate more heat. A 220 lb hiker needs roughly 40% more water than a 155 lb hiker at the same conditions. This calculator scales with body weight, but conditioning matters too — well-trained athletes are more efficient with water than untrained hikers, and acclimatized desert dwellers sweat less than visitors from cool climates.
Cold-Weather Hydration
Below freezing, water needs drop to 0.3-0.4 L per hour but stay important. Cold air is dry and sucks moisture from your respiratory tract. You don't feel thirsty in the cold, which leads to dehydration without warning. Common winter hiking failure: people don't drink because they don't feel thirsty, then bonk halfway up the climb. Force yourself to drink on schedule, and use insulated water bottles or hot tea in thermoses to prevent freezing.
Electrolyte Strategy
For hikes over 3-4 hours, especially in heat or at high intensity, plain water alone can cause hyponatremia (low blood sodium). Symptoms: nausea, headache, confusion, severe in extreme cases. Use electrolyte tabs (Nuun, LMNT, Liquid IV, SaltStick) at a rate of 1-2 servings per liter on hot or hard days. Salty snacks (jerky, pickles, salted nuts, peanut butter) cover sodium losses through food. The simplest rule: if you're sweating visibly, alternate plain water with electrolyte drinks.
Plan With Other Outdoor Tools
Pair this with our water purification time calculator for treating backcountry sources, our hiking time calculator, our backpacking food weight calculator, our calorie burn calculator, and our sun protection time calculator.