How much water should you carry on a hike?
About half a litre17 ounces an hour on an easy hike in mild weather, and about a litre34 ounces an hour on an intense hike in the heat. For 12 km7.5 miles with 400 m1,310 feet of climbing, about 3 h 4 min on the move, that is about 1.75 L52 oz in mild weather and 3.25 L104 oz in the heat, before any refills on the way.
Your result
Carry 2.25 L69 oz from the start.
- Water for the whole route
- 1.75 L52 oz, at 0.5 L17 oz an hour
- Time on the move
- 3 h 4 min, estimated with Naismith's rule
- Weight of the water
- about 2.25 kg4.5 lb at the start
That is more than CDC/NIOSH advise drinking in an hour (about 1.4 L48 oz). Too much water with too little salt can cause hyponatremia.
How it works
Water for the route is litresounces an hour × hours on the move. Without hours, the time comes from Naismith's rule: 12 minutes per kilometre plus 10 minutes per 100 metres of climbingabout 19 minutes per mile plus about 3 minutes per 100 feet of climbing. With places to refill, the route is split into equal stretches, and you carry one stretch of water plus the reserve.
The rates are based on weather and difficulty: half a litre17 ounces an hour for an easy hike in mild weather, and a litre34 ounces an hour for an intense hike in the heat. Warm/moderate is halfway between the two. Litres are rounded up to the next quarter litre.Ounces are rounded up to the next whole ounce.
Measure your own rate
Weigh yourself before and after a hike of known length, add the litresounces you drank, and divide by the hours. One kilogram lost is about one litre.One pound lost is about 15 ounces. Put the result in "Your own rate".
Refilling on the way
The Fontavio app shows drinking water points on the map, including ones other people have confirmed. You can see what's closest or pick a place on the map, then follow the compass or use navigation. With Pro, the route planner lets you pick the water stops along the way and open them in Google Maps as one trip.
Frequently asked questions
How much water should you carry when hiking?
About half a litre an hour on an easy hike in mild weather and about a litre an hour on an intense hike in the heat. Less water needs carrying when there are places to refill on the way.
About 17 ounces an hour on an easy hike in mild weather and about 34 ounces an hour on an intense hike in the heat. Less water needs carrying when there are places to refill on the way.
How much water do you need for a day hike?
For six hours on the move, about 3 L in mild weather and 6 L in the heat, by the rates above. With one refill halfway, you carry half of that at a time.
For six hours on the move, about 102 oz in mild weather and 203 oz in the heat, by the rates above. With one refill halfway, you carry half of that at a time.
How much water do you need for a 10 km hike?
With 500 m of climbing, Naismith's rule gives about 2 h 50 min on the move, so about 1.5 L in mild weather and 3 L in the heat.
10 km is 6.2 miles. With 1,640 feet of climbing, Naismith's rule gives about 2 h 50 min on the move, so about 1.5 L in mild weather and 3 L in the heat.
With 500 m of climbing, Naismith's rule gives about 2 h 50 min on the move, so about 48 oz in mild weather and 96 oz in the heat.
10 km is 6.2 miles. With 1,640 feet of climbing, Naismith's rule gives about 2 h 50 min on the move, so about 48 oz in mild weather and 96 oz in the heat.
Can you drink too much water on a hike?
Yes. CDC/NIOSH advise not drinking more than 48 ounces, about 1.4 litres, an hour, because too much water with too little salt can cause hyponatremia, a medical emergency. On long hot hikes, eat salty food along with the water.
Yes. CDC/NIOSH advise not drinking more than 48 ounces an hour, because too much water with too little salt can cause hyponatremia, a medical emergency. On long hot hikes, eat salty food along with the water.
How do you work out your own sweat rate?
Weigh yourself before and after a hike of known length, add what you drank, and divide by the hours: one kilogram lost is about one litre.
Weigh yourself before and after a hike of known length, add what you drank, and divide by the hours: one pound lost is about 15 ounces.
Sources
- Visit Utah, How much water to pack for your Utah adventure (opens in a new tab) (checked 2026-10-20)
- US National Park Service, Big Bend: hike smart (hyponatremia) (opens in a new tab) (checked 2026-10-20)
- CDC / NIOSH, Heat stress: hydration (2017) (opens in a new tab) (checked 2026-10-20)
- American College of Sports Medicine position stand: Exercise and fluid replacement (2007) (opens in a new tab) (checked 2026-10-20)
- Naismith's rule (opens in a new tab) (checked 2026-10-20)
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