Everyone knows that you need to drink more water while hiking than home. And depending on your activity, you need to drink more or less water while hiking. But how much water do you need? And how do you know when you need more or less water?
A lot of it.
You’ll be walking for long periods, and you need to replace the water you’ll lose through sweat and breathing. At the same time, you don’t want to take on too much water. It’ll make you feel bloated and gassy, and you won’t be able to taste the water, either.
To figure out how much water to bring backpacking, you first need to know why you’re bringing it.
Are you going on a short backpacking trip? A long thru-hike? Or a weekend trip? Figure out your duration, activity level, and calorie need to determine how much water you need.
After that, you can figure out how much water you need to bring. Here are some solid tips for how much water you need to bring backpacking.
How much water do you need for a backpacking trip?
The amount of water depends on your activity level, duration, and calorie intake.
You’re a fit, healthy person who weighs around 130 lbs (59 kg). For example, to eat enough calories to support a 20-mile (32 km) trek, you’d need to bring 3 lbs (1.36 kg) of food. This means you need to bring enough water to replace the water you’ll sweat out during a 20-mile hike.
How much water do you need to replace the water you’ll lose through sweat? This is a question you have to answer for yourself.
A good rule of thumb is to replace 1 liter (0.26 gallon) of water for every pound you lose through sweat. If you weigh 130 lbs, you need to bring 130 x 1 = 131.6 ml of water.
How to figure out how much water you need
Step 1: Calculate your base metabolic rate
The number of calories you burn each day is just resting and doing nothing. The number of calories you need to eat for proper nutritional intake is the minimum amount of calories you need to stay healthy.
How much you eat over your base metabolic rate depends on your caloric intake. You can use a calorie calculator or look this up on a food-finder website to figure out how many calories you need per day.
Once you know that, find out how much water a particular number of calories provides. This varies depending on what you’re eating, but a good estimate is one liter of water for every 1000 calories of food eaten.
Serving sizes vary from person to person, so the amount of food that seems like a “large” portion for one person may be only “a little bit” for another.
Step 2: Calculations
Let’s look at three possible scenarios:
Hiking (20 miles each way) Backpacking (light load/no stove), enough food for seven days of hiking, and 3 liters of water per day. Mountaineering (heavy load/stove) with rations for five days and 3 liters of water per day. Each scenario is calculated below:
Hiking: 20 miles in both directions makes it 40 miles total, so someone who hikes would cover 2x the distance they would hike if they only hiked one way (ex. 20 miles out and the way back is 6 x 20 = 120 miles).
Because of this, the 40-mile distances need to be divided by 3, which is how many liters of water you should bring, so you’d need 10 liters of water (40/3)!
Mountaineering: 5 days where you hang out in one spot for all five days means 1 liter for every day of the trip. You don’t have to deal with trekking extra calories, so you only have to worry about paying your basal metabolic rate or BMR.
Even at high activity levels, a good estimate for your BMR is about 1000 calories per day. If that’s so, then for a 5-day trip, you’d need 5000 calories or .5 kg.
There are 1000 ml in a liter; 50 liters in 50kg, meaning there would be 0.0156kg per liter. 5 x 0.0156~ = 0.072 kg, which when rounded gives 7kg, so that’s how much food fuel we’re talking about… And 3 liters of water (note how it also says “per day”…)
Use the Harris-Benedict equation to determine how many calories you need to eat.
Calculating Your Basal Metabolic Rate (BMR)
Do a little math to find out how many calories you’re burning per hour. Divide your body weight by your BMR and multiply the result by 60.
For example, if your BMR is 2000 calories and you weigh 140 pounds, you’ll know that you’re burning 140/2000 x 60 = 25 calories per hour.
How to weigh your water needs
If you’re on the trail, weighing your water is a must. It’s the only way to make sure you’re bringing enough water.
You can use a water-specific scale like the Kifaru Hydro Scale or the OMM 5-Gallon Hydration Scale combined with Insight’s hiking app.
Weighing your water is easy to ensure you’re bringing enough water. You have to use the scale to weigh your water and then take the same amount on your hike. You’ll never have to worry about not having enough water.
Factor in your activity level
One of the most important factors to consider when figuring out how much water to bring is how active you are.
The more active you are, the more water your body needs to stay healthy and function correctly. If you’re a very active person, you might need to bring twice as much water as someone less active.
Does this mean that a couch potato will only need half as much water as an athlete? No. Many factors impact how much water you need on the trail, but activity level is one.
Enough water is important for everyone. You don’t want to start a hard hike in the backcountry dehydrated. 2 to 4 liters of water per day is adequate for most people, depending on your activity level and personal needs.
It is important to be aware of the signs of dehydration like thirst, intense headaches, confusion; disorientation; constipation; and dark yellow urine (if you have to use the bathroom).