How many liters of water should I bring on a day hike?

As a guide, drink 70–80% of fluid loss (body weight kg × walking hours × 5 ml) and add a reserve. A 60 kg person walking for 5 hours loses about 1,500 ml, drinks 1,050–1,200 ml, and with a 500 ml reserve carries about 1.7 L (four 500 ml bottles). Bring more on hot summer days or if you sweat easily.

What is the route constant?

It’s a number expressing how hard a hiking course is, devised by Masayoshi Yamamoto of the National Institute of Fitness and Sports in Kanoya. Route constant = 1.8 × course time (hours) + 0.3 × walking distance (km) + 10.0 × cumulative elevation gain (km) + 0.6 × cumulative elevation loss (km). Multiply it by the total of body weight and pack weight (kg) for a guide to the energy (kcal) used on that course. Because the coefficient for elevation gain is large, the greater the elevation gain, the harder the number even for the same distance.

How many kcal of trail food do I need for hiking?

Eat part of the energy used (route constant × (body weight + pack weight)) while hiking. For example, walking a course with a route constant of 22.6 at 60 kg body weight with an 8 kg pack uses about 1,540 kcal, and 50% of that is about 770 kcal (around two rice balls, one yokan bar, one bag of nuts, and a few candies). Eating a little at each break rather than a lot at once helps prevent bonking.

What if I don’t know the course time?

You can estimate it from distance and cumulative elevation gain and loss. This tool uses the German standard DIN 33466 method (time at 4 km/h on flat ground, 300 m/h uphill, and 500 m/h downhill, then adding half of the shorter of the horizontal and vertical times to the longer). For example, 10 km with 1,000 m up and 1,000 m down is about 6 hours 35 minutes. If you have the course time from a trail map, enter that instead.

How is the summit temperature calculated?

Temperature drops about 0.6°C for every 100 m of altitude. If it’s 20°C at a trailhead at 600 m, a 1,600 m summit is about 20 − 0.6 × 10 = 14°C. Wind chill also drops about 1°C per 1 m/s of wind, so with 5 m/s of wind it feels like about 9°C. Forecast temperatures are for the foot of the mountain, so you often need a jacket at the summit.

Hiking Water & Trail Food Calculator | Calories Burned by Route Constant, Water to Carry, Summit Temperature & Clothing

Answers “how many liters of water should I bring?” and “how many kcal of trail food?” for a day hike from your route and body. Energy use is the route constant by Masayoshi Yamamoto (1.8 × course time + 0.3 × distance + 10 × elevation gain + 0.6 × elevation loss) × (body weight + pack weight), and fluid loss is body weight × walking time × 5 ml. It shows the water to carry, the amount to drink (70–80% of fluid loss) plus a reserve, as a number of 500 ml bottles. If you don’t know the course time, you can estimate it from distance and elevation with DIN 33466. It also gives how much to drink and eat at each break interval, suggested quantities of trail food such as rice balls, yokan, and nuts, and a clothing guide for the summit from the temperature drop with altitude (0.6°C per 100 m) and wind chill. You can copy the plan and share it on messaging apps.

1. Enter the course

Enter the “course time (excluding breaks)”, distance, and cumulative elevation gain and loss from a trail map or app. For a loop, gain and loss are about the same.

Course time

Time

Walking distance

Cumulative elevation gain

Cumulative elevation loss

If you don’t know the course time: estimated from distance and elevation, it’s 6 h 35 min (DIN 33466: 4 km/h flat, 300 m/h up, 500 m/h down)

2. Body weight, pack & pace

Energy used is proportional to “body weight + pack weight”. Enter the starting pack weight including water and food.

Body weight

Pack weight

Your pace (walking time = course time × multiplier)

3. Water and trail food needed

Energy used comes from the route constant (Masayoshi Yamamoto), and water lost through sweat and breathing (fluid loss) from body weight × walking time × 5.

Water to carry

1,700ml

4 × 500 ml bottles (up to 1,200 ml to drink + 500 ml reserve)

Amount to drink while hiking

1,050–1,200ml

70–80% of about 1,500 ml fluid loss

Energy used

1,510kcal

Route constant 22.6 × (60 + 7) kg

Target to eat while hiking

760kcal

50% of energy used (adjustable below)

Route constant (course difficulty)

22.6

Hard (day hikes with about 1,000 m elevation gain)

Walking time

5 h

Course time 5 h × 1 (excluding breaks)

Share to eat while hiking (% of energy used)

Your body has stores of carbohydrate and fat, so you can keep walking without eating everything you burn on the spot. But too little leads to bonking (running out of energy), so the default is 50%.

Water reserve (for getting lost, heat, instant noodles, etc.)

4. Drinking & eating per break

A little at a time, before you get thirsty or hungry. A guide assuming breaks based on walking time.

Drink per break

240ml

5 breaks (including the end)

Eat per break

150kcal

About 0.8 rice balls’ worth

Break 11:00Walked so far
Break 22:00Walked so far
Break 33:00Walked so far
Break 44:00Walked so far
End of hike5:00Walked so far

5. Trail food combination

Choose what you’ll bring and correct the calories per piece to match your package labels. “Allocate to target” suggests quantities.

Total of selected trail food0 / 760 kcal

About 760 kcal to go. Adding things you can eat while walking, like candy or glucose tablets, makes it easier to keep going.

6. Summit temperature & clothing

Temperature drops about 0.6°C for every 100 m of altitude, and wind chill drops about 1°C per 1 m/s of wind. Forecast temperatures are for the foot of the mountain.

Trailhead elevation

Trailhead temperature

℃

Summit elevation

Summit wind speed

m/s

Summit temperature

14℃

Elevation difference 1,000 m × 0.6°C/100 m

Wind chill

9℃

Wind 5 m/s × about 1°C

Add an insulating layer (fleece, light down)

You’ll get cold quickly at breaks and on the summit. A hat and gloves are reassuring.

Copy & share the plan

Paste it into a messaging app or notes to share the load with your hiking partners. The URL contains the course, body weight, and temperature settings.

[Hiking water & trail food plan]
Course: course time 5 h, 10 km, up 1,000 m, down 1,000 m
Body 60 kg + pack 7 kg / walking time 5 h
Route constant 22.6 (Hard (day hikes with about 1,000 m elevation gain))
Energy used about 1,510 kcal / target to eat while hiking about 760 kcal (50%)
Fluid loss about 1,500 ml / drink 1,050–1,200 ml
Water to carry 1,700 ml (4 × 500 ml bottles, including 500 ml reserve)
Breaks every 60 min × 5: about 240 ml and 150 kcal each
Summit (1,600 m) temperature about 14°C, feels like about 9°C at 5 m/s wind: Add an insulating layer (fleece, light down)

The numbers are guidelines from exercise physiology formulas and vary greatly with heat, humidity, physical condition, and load. Bring extra water for low mountains in summer and courses with little tree cover, and plan with a margin. What you enter is only saved in this browser and is not sent to a server.

ABOUT

About Hiking Water & Trail Food Calculator | Calories Burned by Route Constant, Water to Carry, Summit Temperature & Clothing

The hiking water & trail food calculator works out “how many liters of water to carry” and “how many kcal of trail food you need” for a day hike from your route and body. Energy use is the route constant devised by Masayoshi Yamamoto of the National Institute of Fitness and Sports in Kanoya (1.8 × course time + 0.3 × walking distance + 10 × cumulative elevation gain + 0.6 × cumulative elevation loss; time in hours, distance and elevation in km), multiplied by the total of body weight and pack weight. Water lost through sweat and breathing (fluid loss) uses Yamamoto’s guideline of “body weight (kg) × walking time (h) × 5” ml, and the amount to drink while hiking is 70–80% of that. This tool shows the “water to carry”, the drinking amount plus a reserve, as a number of 500 ml bottles, and also suggests how much to drink and eat per break interval and quantities of trail food such as rice balls, yokan, and nuts. If you don’t know the course time, you can estimate it from distance and elevation using the formula in the German standard DIN 33466. It also calculates the summit temperature and a clothing guide from the roughly 0.6°C drop per 100 m of altitude and the roughly 1°C drop in wind chill per 1 m/s of wind.

How to use Hiking Water & Trail Food Calculator | Calories Burned by Route Constant, Water to Carry, Summit Temperature & Clothing

1Look up the course time (excluding breaks), walking distance, and cumulative elevation gain and loss on a trail map or app and enter them (if you don’t know them, choose an example course or estimate from distance and elevation)
2Enter your body weight and the starting pack weight including water and food, and choose your pace (how many times the course time you walk)
3Check “Water to carry”, “Amount to drink while hiking”, “Energy used”, and “Target to eat while hiking”
4Choose a break interval (every 30–90 minutes) and check how much to drink and eat at each break
5Choose the trail food you’ll bring, correct the calories to match the package labels, and decide quantities with “Allocate to target”
6Enter the trailhead elevation and temperature and the summit elevation and wind speed to check the summit wind chill and a clothing guide
7Paste the plan into a messaging app or notes with “Copy plan” and share the load with your hiking partners

Great for

Find out how many liters of water to bring on your first day hike
Review the amount because you ran out of water, or had too much left, last time
Decide how many kcal and how many pieces of trail food to bring
Decide how much to eat at each break to prevent bonking (running out of energy)
Compare route difficulty with the route constant to choose your next mountain
Find the summit temperature and wind chill when the forecast only gives the temperature at the foot of the mountain
Share water and trail food amounts with members of a group hike

Good to know

The course time for the route constant is the standard course time (excluding breaks) shown on trail maps and the like. Your pace multiplier is applied only to fluid loss and break planning (walking time).
Energy use is proportional to “body weight + pack weight”. Include the weight of the water and food you carry in the pack weight (1 L of water is about 1 kg).
Fluid loss (body weight × walking time × 5 ml) is a guideline for average conditions. On hot summer days, humid days, and courses with little tree cover, you’ll sweat more than this. Increase your water reserve.
Drinking 70–80% of fluid loss reflects that you don’t need to replace all the water lost in sweat at once; drinking a little at a time before you get thirsty is recommended.
The share eaten while hiking (50% by default) is a guideline set by this tool. Your body has stores of carbohydrate and fat, so you don’t need to eat everything you burn on the spot, but increase it for longer courses. If you’re having lunch, count it as part of this.
Trail food calories vary by product. The defaults are guidelines, so correct them to match the labels on your packages.
The “light” to “very hard” route constant categories are guidelines used by this tool.
Summit temperature is calculated assuming a 0.6°C drop for every 100 m of altitude. Wind chill uses the guideline of about 1°C lower per 1 m/s of wind, and it also varies greatly with sunshine, humidity, and wet clothes from sweat.
What you enter is only saved in this browser and is not sent to a server.

Questions this tool answers

Use Hiking Water & Trail Food Calculator | Calories Burned by Route Constant, Water to Carry, Summit Temperature & Clothing for searches like these:

I want to know how much water to bring on a day hike
I want to know how many kcal of trail food I need for hiking
I want to know how to calculate the route constant
I want to calculate hiking calories burned including pack weight
I want to estimate course time from distance and elevation
I want to calculate the summit temperature and wind chill
I want to know how much to drink and eat at each hiking break

FAQ

How many liters of water should I bring on a day hike?: As a guide, drink 70–80% of fluid loss (body weight kg × walking hours × 5 ml) and add a reserve. A 60 kg person walking for 5 hours loses about 1,500 ml, drinks 1,050–1,200 ml, and with a 500 ml reserve carries about 1.7 L (four 500 ml bottles). Bring more on hot summer days or if you sweat easily.
What is the route constant?: It’s a number expressing how hard a hiking course is, devised by Masayoshi Yamamoto of the National Institute of Fitness and Sports in Kanoya. Route constant = 1.8 × course time (hours) + 0.3 × walking distance (km) + 10.0 × cumulative elevation gain (km) + 0.6 × cumulative elevation loss (km). Multiply it by the total of body weight and pack weight (kg) for a guide to the energy (kcal) used on that course. Because the coefficient for elevation gain is large, the greater the elevation gain, the harder the number even for the same distance.
How many kcal of trail food do I need for hiking?: Eat part of the energy used (route constant × (body weight + pack weight)) while hiking. For example, walking a course with a route constant of 22.6 at 60 kg body weight with an 8 kg pack uses about 1,540 kcal, and 50% of that is about 770 kcal (around two rice balls, one yokan bar, one bag of nuts, and a few candies). Eating a little at each break rather than a lot at once helps prevent bonking.
What if I don’t know the course time?: You can estimate it from distance and cumulative elevation gain and loss. This tool uses the German standard DIN 33466 method (time at 4 km/h on flat ground, 300 m/h uphill, and 500 m/h downhill, then adding half of the shorter of the horizontal and vertical times to the longer). For example, 10 km with 1,000 m up and 1,000 m down is about 6 hours 35 minutes. If you have the course time from a trail map, enter that instead.
How is the summit temperature calculated?: Temperature drops about 0.6°C for every 100 m of altitude. If it’s 20°C at a trailhead at 600 m, a 1,600 m summit is about 20 − 0.6 × 10 = 14°C. Wind chill also drops about 1°C per 1 m/s of wind, so with 5 m/s of wind it feels like about 9°C. Forecast temperatures are for the foot of the mountain, so you often need a jacket at the summit.

Special Thanks

SOLO GUILD | サービス作るAIエンジニア

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