Hiking Water Between Resupply Points Calculator
Calculate water needed between trail resupply points by distance, hiker weight, temperature, and difficulty.
Returns liters, bottles, and water weight.
Water is the heaviest thing in a thru-hiker’s pack. A liter weighs 2.2 lb. Carrying enough for a 25-mile dry stretch in summer means hauling 12+ pounds of water. Get the calculation wrong and you bonk; get it conservative and you suffer the weight needlessly.
Baseline rates by conditions.
- Cool weather (under 70°F), easy trail: 0.5 L per hour of hiking
- Warm (70-85°F), moderate trail: 0.75 L per hour
- Hot (85-95°F) or strenuous: 1.0 L per hour
- Desert / over 95°F: 1.5 L per hour minimum
- Cold (below 40°F): people forget to drink and dehydrate; still need 0.5 L/hr
The formula. Water (L) = (hours hiking × hourly rate) + camp water + safety margin.
Camp water is 0.5 to 1 L for cooking, drinking, and hygiene per overnight. Safety margin is 1 L extra in normal conditions, 2 L in desert.
Body weight matters more than people think. A 200 lb hiker burns roughly 30% more water than a 140 lb hiker on the same trail at the same pace. The hourly rates above assume ~160-170 lb. Scale linearly: divide your weight by 165 and multiply.
Pack weight effects sweat rate too. A 35-lb pack on hilly terrain pushes water needs up 20-30% above the baseline. Day-hikes with a 10-lb pack are at the low end of the rate ranges.
The dry-stretch reality check. PCT hikers in the Mojave routinely cover 25-35 miles between water sources. At a 2.5 mph average that is 10-14 hours of hiking. At 1 L/hr in heat, that is 10-14 L (22-30 lb) of water alone. Most carry less and ration aggressively. Dehydration is the #1 evacuation reason in the desert section.
Filtration adds a planning layer. A Sawyer Squeeze filters about 1 L/min. If you stop at a water source for 15 minutes to filter and drink, you can leave with 5 L on you and 1 L gulped. Plan stops, not just carries.
Worked example. 18-mile dry stretch, 80°F, moderate trail, 170 lb hiker, no overnight.
- 18 miles / 2.5 mph = 7.2 hours
- 0.75 L/hr × 7.2 = 5.4 L
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- 1 L safety margin = 6.4 L total
- Weight: 6.4 × 2.2 = 14.1 lb of water
Tips for carrying less safely.
- Drink 1 L right at the source before leaving (camel up)
- Dry camp early when possible — saves carrying overnight water
- Hike early and late to avoid peak heat hours
- Cache water beforehand on long known-dry stretches