Don't Guess the Trail. Calculate Your Exact Hydration Needs
Stay safe on every adventure. Use the scientific method trusted by backpackers to determine exactly how much water to carry—no more, no less.
Overpacking water breaks your back. Underpacking water breaks your trip
We’ve all been there. Lugging a 10-pound water bladder up a mountain, only to dump half of it out at the summit. Or worse, running out of water two miles from the trailhead with the sun beating down.
Hydration isn’t just about comfort; it’s about safety. Dehydration leads to fatigue, cramping, and poor decision-making.
Most hikers rely on a “one-size-fits-all” guess. But your water needs change based on temperature, effort, and duration.
The Hiking Water Calculator: Built on Sports Science, Not Guesswork.
Our calculator isn’t just a random formula. It’s based on guidelines from the American Hiking Society and hydration studies from the National Institutes of Health (NIH) .
We factor in the variables that matter most:
- Duration: The longer you're out, the more you sweat.
- Temperature: Heat index directly impacts fluid loss.
- Intensity: A steep incline doubles your required intake compared to a flat walk.
- Body Weight: (Optional) We personalize the math for your specific physiology.
Feature List
Instant Results
Get your number in seconds.
Mobile Friendly
Works on the trail, right from your phone.
Practical Advice
We don't just give you liters. We tell you how many standard 32oz Nalgene bottles that is.
How It Works
Get Your Number in Three Steps
Step 1
Enter your hike details (Time, Temp, Difficulty).
Step 2
(Optional) Add your weight for precision.
Step 3
Get your result and hit the trail prepared.
Trail Wisdom: 3 Hydration Rules We Live By
Get Your Number in Three Steps
The "Plus 0.5L" Rule
Always add half a liter to your calculated number. This is your emergency buffer for delays, wrong turns, or helping a fellow hiker in need.
Electrolytes Matter
If your hike is over 2 hours or in high heat, plain water isn’t enough. Pack electrolyte tablets or powders to prevent hyponatremia (water intoxication).
Sip, Don't Chug
Your body absorbs water better if you take small, frequent sips every 15-20 minutes rather than chugging a liter at a rest stop.
Frequently Asked Questions.
Altitude increases your respiratory water loss. While our calculator focuses on temp and exertion, we recommend adding an extra 10-20% to your result for any hike above 8,000 feet.
Absolutely. If you select “Difficult” intensity, the formula adjusts for the higher exertion rate of running.
If you’re using standard 1-liter smartwater bottles (popular for hiking), that’s 3 bottles. If you’re using a 32oz Nalgene, that’s roughly 3 bottles as well (since 32oz is just under 1 liter).