💧 Water Needs Calculator
Enter how long you'll be hiking, how hard you'll work, and the temperature to estimate how much water to carry — with a hot-weather bump — in litres and millilitres.
🧮 Plan Your Water
What is a Water Needs Calculator?
It turns a few trip details into a water target. Based on your hours on trail and how hard you'll be working — light, moderate, or intense — it estimates the total to carry, then increases it by half again when the temperature climbs above 30°C to account for heavier sweating.
Getting hydration right is a balance: too little risks fatigue and dehydration, while too much adds unnecessary weight, since water is about a kilogram per litre. Use the estimate to decide how much to carry and where to refill, and always pack a sensible margin for the unexpected.
❓ Frequently Asked Questions
How much water should I carry when hiking?
A common starting point is around half a litre of water per hour of moderate hiking, more in heat or on hard effort and less on an easy stroll. This tool estimates your total from time on trail and intensity, then adds 50% when the temperature is above 30°C.
How does heat change how much water I need?
Hot weather dramatically increases fluid loss through sweat. Above about 30°C this calculator raises the estimate by 50% to reflect that, but conditions like direct sun, humidity, and altitude can push needs higher still — always carry a margin.
Should I carry all my water or plan to refill?
Water is heavy — roughly one kilogram per litre — so on longer routes many hikers carry less and refill at reliable sources, treating or filtering along the way. Map your resupply points before you go and only carry all your water when sources are scarce or unreliable.
What are the signs I'm not drinking enough?
Dark urine, headache, dizziness, fatigue, and cramping can all signal dehydration. Sip regularly rather than waiting until you're thirsty, and increase intake in heat, at altitude, and on strenuous climbs. These estimates are guidance, not a substitute for paying attention to how you feel.