What size dry bag do I need

Pick the wrong size and you either can't close the bag or carry dead air for miles. Dry bag sizing is straightforward once you know which category each item falls into.

How roll-top closures reduce usable volume

Every roll-top dry bag requires three to four full rolls before the buckle clips. Those folds eat into the top 10–20 cm of the bag. On a 10L bag that typically translates to 1.5–2L of unusable space. On a 5L bag the loss is proportionally larger: you may only get 3.5L of practical capacity.

The fix is simple: when an item is borderline, go one size up. A sleeping bag that just barely fits a 20L bag will fight you every morning. A 25L bag gives you working room and a proper seal.

Sizing by use case

2–5L (small valuables): A 2L bag fits a phone, a folded bandana, and a small wallet with room to seal. A 5L bag handles a point-and-shoot camera, a passport wallet, and a headlamp. These small bags are also where quality matters most: look for welded seams rather than glued seams at this size.

10–20L (clothing): A synthetic mid-layer and a base-layer top fit comfortably in a 10L bag. A full set of camp clothes (top, bottom, socks, underwear) fits in 15L with a clean seal. If you're packing a rain jacket alongside other soft layers, step up to 20L.

20–35L (sleeping bag): Most three-season down bags (rated 15°F to 32°F) compress into the 20–25L range. A bulkier synthetic bag in the same temperature range needs 30–35L. Check your bag's packed size before you buy a dry bag for it; manufacturers list this dimension on the product page.

35L+ (pack liner): A 35–45L roll-top dry bag like the Sea to Summit Lightweight Dry Bag 35L used as a pack liner protects everything inside your main pack. It is not a stuff sack for one item; it is a waterproof envelope for the whole load. Size it to match your pack's main compartment, not to the brim.

Kayaking vs backpacking: different priorities

Kayakers face a hard volume ceiling. A sea kayak day hatch is typically 50–80L total, and you share that space with safety gear. Oversized bags mean wasted air pockets that shift in following seas. Backpackers face a weight ceiling instead: extra dry bag material adds up, which is why a single liner is often the smarter call for multi-day trips.

In a kayak, dead air is dead weight; in a pack, too many small bags become a sorting puzzle at camp.

The multi-bag organization system

Using one giant bag for everything creates a problem: you have to unpack to find anything. A three-bag system solves this without adding meaningful weight.

• Sleeping bag in its own 20–35L bag. It goes in last, at the bottom of the pack or in the stern hatch, and you don't dig through it until camp.
• Clothing in a 10–20L bag. Mid-pack or in the bow hatch. You reach this once at camp, not throughout the day.
• Valuables and navigation in a 2–5L bag. Top of the pack or a hip belt pocket. You reach this constantly.

This system means the bag you open most often is the smallest and lightest. It also means a hatch flood or a river swim compromises at most one category of gear.

Frequently asked questions

For specific picks, see our guide to the best dry bags. Browse all hike guides or read how we research and rate gear.