Water Carry Planner
Liters per day from temperature, humidity, altitude, exertion, and pack weight — then converts to bottles per km.
Trip inputs
Result
A natural placement between the calculator and the explanation.
What this solves — and what it doesn't
Generic calculators give hikers 0.5 L per hour or 3 to 4 L per day, but those numbers were derived from temperate forest hiking. In hot, dry, or high environments, real demand is much higher — 1 L/h in desert summer is not unusual. This planner starts at 0.5 L/h and adjusts upward for temperature above 20 C, dryness below 60% RH, altitude above 1,500 m, and your chosen effort level.
The other half of the tool is the carry — multiply your daily need by the number of days between reliable refills. That gives the liters you must physically haul, which directly drives pack weight and route choice.
How to read the result
Read the result as three numbers, not one:
- Liters per hour — your steady-state sipping target. Drink early; dehydration sneaks up.
- Liters per day — for planning filter treatment and food-cooking water.
- Liters to carry — the constraint that decides your refills and may force a shorter day.
Add at least 0.5 L for cooking if you’re making hot food; add more in freezing conditions where melting snow is your source.
Limitations
- Acclimatization matters. First 3 to 5 days at altitude, you lose more fluid than usual; the formula’s altitude bump is small. Real demand may be 25 to 40% higher.
- Sweat variability. Salt intake, fitness, and prior hydration all shift the answer ±0.5 L/day.
- Water source reliability. In dry seasons, plan for dry beds and carry more.
- Cold weather. Below 0 C you may drink less voluntarily but still lose moisture through breathing; add hot drinks.
Frequently asked questions
How do I treat brackish or mineralized water?
Increase the carry requirement by 1 day for bad sources. Our tool assumes you’ll drink whatever you find after treatment.
Does drinking more water prevent altitude sickness?
No. Hydration helps you feel better but does not prevent AMS. Adequate acclimatization is the only proven prevention. Don’t let overhydration become hyponatremia risk on big days.
Should I drink until my urine is clear?
Useful rule of thumb on hot days, but not at altitude (where urine is naturally concentrated at night) or in cold weather. Use thirst + planned schedule as the primary signal.