A dry bag is a flexible, roll-top sack that keeps its contents dry by sealing out water—not by withstanding submersion.
Whether you’re kayaking a river, camping in a downpour, or just heading to the beach, a dry bag is the simplest way to keep your phone, clothes, and gear dry. It works on a cleverly simple principle: fill it, roll the top down several times, and clip the buckles shut. The folds create a watertight seal that keeps splashes and rain out. The one thing to know before buying is that most dry bags are rated for splashes, not for fully sinking underwater—so the best choice depends on how wet things will actually get.
What Makes a Dry Bag Work
A dry bag seals through a roll-top closure. You open it wide, place your gear inside, then fold the reinforced top edge down in a few tight rolls until both side buckles can clip snugly against the body of the bag. The multiple folds form a watertight barrier.
How many rolls is enough? Trekitt’s guide puts the typical range at 3–5 rolls. The key is firm, even rolls that compress the top edge tightly—loose or uneven folds can leak.
Materials vary by brand and intended use: PVC, nylon, vinyl, TPU, and laminated ripstop nylon are the most common. Heavier PVC bags are tough and affordable; lighter TPU or ripstop nylon bags pack down small and weigh almost nothing, which is why ultralight backpackers prefer them.
What a Dry Bag Is and Isn’t
Dry bags are built to keep splashes, rain, and brief dunks from soaking your gear. They are not a substitute for hard waterproof cases when you need impact protection, and they aren’t fully submersible containers.
There are two main styles:
- Sack-style—a simple cylindrical bag with a roll-top, best for stuffing into a canoe hatch or duffel.
- Backpack-style—a dry bag with shoulder straps, so you can carry it like a daypack while hiking in wet conditions.
One common confusion: a dry bag can also carry wet items (like a damp swimsuit) so they don’t soak the rest of your luggage—but that’s a use case, not a different product category.
Common Dry Bag Sizes and Uses
Dry bags come in a wide range of volumes, from small 3-liter pouches for a phone and keys to 100-plus-liter haulers for multi-day expeditions. The right size depends entirely on what you’re carrying and how long you’ll be out.
| Size Range | Best For | Example Specs |
|---|---|---|
| 1.5–5 L | Phone, wallet, keys, small electronics | |
| 8–13 L | Day trip clothes, towel, lunch, camera | |
| 20–35 L | Overnight gear, wetsuit, sleeping bag | Sea to Summit Lightweight 20L fits in a pack’s main compartment |
| 50–75 L | Multi-day expeditions, duffel replacement | |
| 79–109 L | Large expedition loads, rafting trips |
For a quick day on the water, a small bag in the 3–5 liter range is all most people need to protect a phone and a change of clothes. If you’re comparing options in that sweet spot, our tested roundup of the best 3L dry bags breaks down the top picks in detail.
Common Mistakes to Avoid
The biggest dry bag failure is user error: not rolling the top enough times. One or two casual folds will leak.
The second is expecting more than the bag can deliver. An IP64 rating means dust-tight and splash-proof, not dive-proof. For kayak trips where the bag might go fully underwater for any length of time, you need a dry box or a fully submersible dry bag with an IP67 or IP68 rating.
Third, don’t overstuff. A bag packed to bursting leaves no room to make tight, even rolls at the top, which defeats the seal. When in doubt, size up.
Finally, many inexpensive bags use a PVC material that’s heavier and less packable than newer TPU options—fine for car camping, but worth skipping if you’re carrying it on your back all day.
A dry bag is one of the most useful pieces of gear you can own for any wet activity. Get the size that fits what you carry, roll it three or four times, and your gear stays dry.
References & Sources
- ORTLIEB. “Dry-bag Heavy Duty Technical Datasheet.” Official specs for IP64 rating, roll closure requirements, and size dimensions.
- Sea to Summit. “Ultra-Sil Dry Bag.” Product page with size range and weights.
- REI. “Dry Bags.” Category overview of dry bag styles and uses.