Enter your body weight, hike distance, trail difficulty, and temperature to find out exactly how much water to bring on your next hike. You'll get a recommended water intake in both liters and ounces, plus a breakdown of how conditions affect your hydration needs.
Recommended Water
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Water in Ounces
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Estimated Hike Duration
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Water Per Hour
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Standard Nalgene Bottles (32 oz)
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The core formula estimates your hourly water need based on body weight, exertion level, temperature, humidity, and sun exposure, then multiplies by your estimated hike duration (distance ÷ pace). Heavier packs, higher temps, and full-sun exposure all increase that hourly rate. A general baseline is about 16–24 oz (0.5–0.7 L) per hour of moderate hiking, scaling up significantly in heat.
A common rule of thumb is half a liter (about 17 oz) per hour of hiking in moderate conditions. For hot, strenuous, or high-elevation hikes, you may need 1 liter or more per hour. Always carry a little extra beyond your calculated need as a safety buffer, especially on trails without water sources.
When you sweat heavily and only replace fluids with plain water, you dilute the sodium in your blood — a condition called hyponatremia. This can cause nausea, headaches, confusion, and in severe cases, serious medical complications. On long or hot hikes, pairing water with electrolytes (sodium, potassium, magnesium) is important.
Yes, especially on hikes longer than 1–2 hours or in hot conditions. Sweat contains sodium and other minerals, not just water. Electrolyte tablets, powder mixes, or salty snacks help you retain hydration, maintain muscle function, and prevent cramping. They're particularly important if you're a heavy sweater.
Early signs include thirst, dry mouth, darker urine, and mild fatigue. More serious dehydration causes headache, dizziness, muscle cramps, and reduced coordination. A good rule: if your urine is pale yellow, you're well hydrated; if it's dark amber, drink more water soon.
Temperature has a major impact. In cool conditions (50–60°F) you might need 12–16 oz/hour, while at 90°F+ that can double to 24–32 oz/hour. Your body ramps up sweating to cool itself in heat, which dramatically increases fluid loss. Sun exposure compounds this further.
Start drinking water 1–2 hours before your hike begins — aim for 16–20 oz in the hour prior. Avoid alcohol and excessive caffeine the night before, as both dehydrate you. Eating a meal with some sodium can also help your body hold onto the fluids you drink before heading out.
Yes. Carrying a heavier pack increases your overall exertion level, which means your muscles generate more heat and your body sweats more. Loads above about 10 lbs start to meaningfully raise your water demand. A 30-lb pack in hot weather can push your hourly water needs up by 20–30% compared to a daypack.