Trip Water Planner
Estimate how much water to carry for a hike based on how long you will be out, the heat, and where you can refill along the way.
Work out what to carry
Answer what you know about the walk. The result is a range, because sweat rates differ between people and days.
What you get back
- A range in litres, never a single figure, because sweat rates differ.
- The one fact doing the most work in that answer.
- What each input changed, and what would change the result.
The planner applies the same rules the full guide explains, so the number it gives you is one you could work out by hand.
- Mild easy hiking
- About 0.5 litre per hour
- Hot or steep hiking
- Up to 1 litre per hour
- Emergency margin
- An extra 0.5 to 1 litre beyond the plan
- Confirmed refill
- Carry to the source plus the margin
- Unconfirmed refill
- Carry the full need
The answer is a range rather than a figure, and that is deliberate. Sweat rates differ between people and between days, so a single number would imply a precision nobody has.
Altitude and group size do not get a multiplier here.
The guide gives a direction for both rather than an amount, so the planner shifts the range upward for altitude and returns a note for a group. Inventing a coefficient would make the output look more exact without making it more true.
Two things this cannot do for you
It cannot confirm a water source. Counting a refill you have not verified is the single most common way a plan turns into a problem, so an unconfirmed source is treated as no source at all.
It also cannot replace measuring yourself. Weighing before and after an hour on trail gives you a personal rate that beats every estimate on this page.