Compact CampingDry bag sizes explained: what actually fits
A litre rating on its own doesn't mean much until you know what actually fills it. Here's a practical mapping from size to real gear, so you're not guessing at checkout.
Small: 3–5 litres
This range suits the items you least want getting wet and that take up almost no space: a phone, a wallet, a headlamp, a first-aid kit, spare batteries. It's the size most people underestimate needing, since it's easy to assume everything can share one bigger bag — a dedicated small bag for electronics specifically means you're not digging through clothing to find your phone.
Medium: 8 litres
Eight litres is close to the sweet spot for a single day's worth of gear: a change of clothes, a rain layer, or a compact sleep system component like a stuffed quilt or liner. Our budget pick, the Sea to Summit Ultra-SIL Dry Bag 8L at 39 g, sits exactly in this range and is the size most people reach for when they only need one bag rather than a set.
Large: 20 litres and up
Once you're packing a multi-day food resupply, a full clothing layer system, or gear for a canoe day where the whole load needs to stay dry, 20 litres or more is where you land. Our dual-purpose pick, the Sea to Summit Ultra-Sil Dry Daypack 22L, sits right at this threshold and does double duty as a genuine wearable daypack, not just a sack you carry inside another pack.
| Size | Typical contents |
|---|---|
| 3–5 L | Phone, wallet, headlamp, first-aid kit |
| 8 L | A day's clothing, rain layer, or a stuffed sleep system component |
| 20 L+ | Multi-day food resupply, full clothing layers, a canoe day's gear |
The headroom rule almost everyone skips
A roll-top dry bag needs to be rolled down at least three times before buckling to actually seal, and that rolled-down section eats into usable space. As a rule of thumb, only plan on filling a dry bag to about 80% of its rated capacity — a 10-litre bag should really only carry around 8 litres of gear, with the rest reserved for the roll. Overfilling makes the roll-top harder to close properly and increases the odds it leaks.
One bag or a set?
A single bag covers one job well; a small set spanning a few sizes solves more real packing problems, since it lets you sort gear by how badly it needs to stay dry and how often you need to reach it. Our top pick, the Sea to Summit Ultra-SIL Dry Bag Set (3L, 5L, and 8L together), covers electronics, a clothing layer, and a sleep system component in one order, which is usually a better match for a real trip than one large bag holding everything loosely.
Verdict
Size to what's actually going inside, not to your pack's total volume, and leave real headroom for the roll. If you're only protecting one category of gear, a single well-sized bag is enough; if you're organising a full kit, a small set beats one oversized bag every time.