How Much Water Should You Carry Bikepacking?

The Numbers

Sweat rate varies between people more than any other figure in this article, so treat these as a starting point you refine on your own rides.

Conditions	Per hour riding	Three hour gap	Six hour gap
Cool, under 15°C	400 to 500 ml	1.5 L	3 L
Mild, 15 to 25°C	500 to 750 ml	2 L	4 L
Hot, 25 to 32°C	750 ml to 1 L	3 L	5.5 L
Desert, above 32°C	1 L or more	3.5 L	Do not plan a six hour dry gap

Add a litre to every one of those numbers. That litre is not for drinking, it is for the source that turned out to be dry, the mechanical that cost you ninety minutes, and the climb that took longer than the profile suggested.

Note the bottom right cell. In genuine desert heat, a six hour dry gap is not a hydration problem you solve by carrying more, it is a route planning problem you solve by not doing it.

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Size To The Gap, Not To The Bike

The most common mistake is deciding capacity from the bike's fittings. Two bottle cages, therefore two bottles, therefore 1.5 litres, therefore whatever happens happens.

Do it the other way round. Find the longest gap between reliable water on your route, convert it to hours at your realistic loaded pace, multiply by the rate above, add a litre, and then work out where that volume goes on the bike.

Sometimes the answer is two bottles. On a desert route with one reliable source it is five litres, which means bottles plus a bladder in the frame bag plus one more in a cargo cage. The bike has to accommodate the water, not the other way around.

Reliable Is Doing A Lot Of Work In That Sentence

A source is reliable if it runs in the season you are riding, in the year you are riding, and you have checked recently. Almost nothing else qualifies.

A creek marked on a map is not a source. A seasonal river crossing is not a source in March. A general store in a settlement of forty people with unpublished off-season hours is not a source. Every one of those can be a bonus, and none of them can be a dependency.

The practical rule is this: carry enough to reach the next source worth betting money on. Anything less certain than that does not belong in the plan.

Where The Weight Goes

Five litres is 5 kg and it is the heaviest thing on the bike by a wide margin. Where you put it changes how the bike rides more than any other packing decision.

Low and central is the answer. A bladder in the frame bag is the single best place for two of those kilos, because it sits inside the wheelbase and below the top tube. Bottles on the down tube and inside the front triangle are next best.

What you do not do is put water in the seatpack. Two litres behind the saddle is 2 kg on the end of a lever, and it will do more damage to the bike's handling than the entire rest of your kit.

The One Rule Worth Memorising

Water is the one weight you never trim to hit a number.

Everything else on the bike is negotiable. You can leave the second layer, the book, the third tube, the camp shoes. You can take a lighter tent. Every one of those is a comfort decision with a bad night as the worst outcome.

Carrying too little water in dry country has a different worst outcome, and it arrives faster than people expect. Carry the full amount, ride slower for it, and come back.