Dry bags solve a simple problem — keep the water out — and then immediately create a confusing one: what size do I buy? They range from tiny 2-liter pouches to 110-liter haulers, and the number on the tag doesn't mean much until you've actually stuffed one.
So here's the cheat sheet, by liter, plus the one mistake that quietly soaks everyone's gear the first time.
The rolling rule that makes it actually waterproof
Before sizing: a roll-top dry bag is only watertight if you leave room to roll the top down at least three times before clipping it. Cram it to the brim and you can only fold it once — and one fold is a splash guard, not a seal. This is the single most common reason people say "my dry bag leaked." It didn't leak. It was overpacked. Always buy a hair bigger than you think so you've got that roll allowance.
What fits in each size
- 2–5L — Phone, keys, wallet, snacks, a power bank. The "valuables pouch" you toss in a kayak or clip to a belt. Great as a backup even inside a bigger pack.
- 10L — A day's worth: a layer, lunch, first-aid kit, electronics, a small camera. The do-everything size for paddling and day hikes near water.
- 20L — The workhorse. A change of clothes plus a layer plus the day-trip stuff, or a compact sleeping setup for an overnight. Big enough to be useful, small enough to still pack into a kayak hatch or lash to a pack. If you're buying one dry bag and one only, this is usually it.
- 30–40L — Weekend kit: sleeping bag, clothes, and food for a multi-day paddle or raft trip. Starts getting awkward to wedge into smaller boats.
- 50L+ — Expedition haulers and gear duffels. Overkill unless you're on the water for days.
The "one big bag" trap
It's tempting to buy a single 40L and call it done. Don't. Two medium bags beat one big one almost every time:
- They wedge into the odd-shaped spaces in a kayak or trunk that one fat bag won't.
- You can keep wet/dirty stuff separate from dry/clean stuff.
- If one gets compromised, you haven't lost everything.
The classic kayak setup is a couple of 10–20L bags fore and aft, plus a tiny one for valuables. For camping and overlanding, a 20L for clothes and a 20L for the kitchen-y odds and ends keeps the chaos sorted.
Where the 20L earns its keep
We landed on 20 liters for our Waterproof Roll-Top Dry Bag because it's the size that does the most jobs. It's a clothes bag for an overnight, a gear hauler for a paddle, a "keep the spare layers dry" bag in the bottom of a pack, and a surprisingly good laundry/wet-swimsuit bag on the drive home. The roll-top closure gives you that all-important three-fold seal, and it clips to a pack or a thwart.
Quick picks
- Just want valuables safe on the water? 5L.
- Day hikes, day paddles, one bag? 10–20L.
- Overnights and weekend trips? A pair of 20L beats a single 40L.
Dry bags live in our Everyday Cache collection — the home for the small, do-everything gear that quietly saves the trip.