Hiking Water Calculator
Know exactly how much water to carry — dehydration is the most common cause of trail emergencies
Your hike
Water to carry
2.6L
Equivalent to 4 × 750ml bottles
What this means
Significant hydration needed
Carry at least 2.6L. A hydration bladder makes this easier than bottles. Consider electrolyte tablets for hikes over 3 hours — water alone does not replace lost sodium.
Breakdown
Carrying 2.6L in bottles is awkward and tiring
A hydration bladder keeps weight centred in your pack and lets you drink hands-free without stopping.
Find on Amazon →How to use the hiking water calculator
Select your hike duration, expected temperature, and exertion level for an instant water carry recommendation. Open Advanced Options to refine for body weight, altitude, sex, and heat acclimatisation. The calculator caps at 4.5L and flags when you should plan water resupply points instead of carrying more.
What affects hydration needs hiking
Temperature is the biggest driver
In hot conditions above 30 degrees, sweat rate roughly doubles compared to a cool day. Most hikers are surprised how much this changes their water needs. The difference between a mild day and a hot day on the same trail can be an extra litre or more.
Exertion multiplies fluid loss fast
A strenuous steep climb in warm weather can push sweat rate to 1.5 litres per hour. At that rate, a 4-hour hike requires serious water planning. The combination of heat and hard effort is where dehydration happens on trail.
Altitude increases respiratory loss
Higher altitude means faster, deeper breathing as your body compensates for lower oxygen. That increases fluid loss through respiration even in cool temperatures. Hikers above 2,500m consistently need more water than at sea level, even on cool days.
Electrolytes are not optional on long hikes
Plain water without sodium replacement risks hyponatremia on hikes over 3 hours in warm conditions. The symptoms are similar to dehydration but the cause is the opposite. If you're carrying 2 litres or more, add electrolyte tablets. The weight is negligible and the difference is real.