What Size Dry Bag Do I Need? 5L to 40L, Sorted by What You Pack
Key Takeaways
- 5L holds pocket contents plus a snack. 10L adds a towel or a change of clothes. 20L is a full day kit. 40L is overnight or group gear.
- Paddling Magazine's sizing runs 5 to 15L for day trips, 16 to 30L for a sleeping bag and pad, and 30 to 50L for single-night trips or raft loads.
- Two medium bags almost always beat one large one. They pack around a hull better, and a single failure does not soak everything.
- Buy roughly 25% larger than your gear measures. A roll-top loses volume to the closure, so a "full" 20L bag carries less than 20L.
- Size is only half the question. A bag that floats and seals without rolling changes what happens when it goes overboard.
The honest answer: most people need a 5L for their phone and wallet, and a 20L for everything else. That covers a beach day, a paddle, a boat day, and a fishing trip. Go bigger only when you are carrying sleep gear or packing for more than one person.
Start With the Load, Not the Liters
Liters mean nothing until you put objects next to them. So here is the translation most size charts skip.
| Size | What actually fits | Best for |
|---|---|---|
| 2L to 5L | Phone, wallet, keys, sunglasses, a snack | Swimming, beach, tubing, a pocket you can trust |
| 10L | The above plus a towel, a t-shirt, a light layer | Kayak day paddle, paddleboard, pool and lake |
| 20L | Full change of clothes, towel, lunch, camera, jacket | Full boat day, fishing trip, day rafting |
| 30L to 40L | Sleeping bag and pad, or two people's day gear | Overnight paddle, group trips, hunting hauls |
| 50L and up | Multi-day personal gear, bulky layers, tents | Expeditions, raft dry storage |
Paddling Magazine lands in the same place. Their guide puts 5L to 15L bags on day trips for snacks, phones, cameras and layers, 16L to 30L for a sleeping bag and pad, and 30L to 50L for single-night trips or gear on a raft or SUP.
Notice what that means for most readers. If you are not sleeping outside, you almost certainly do not need more than 20L.
The Sizing Mistake Nearly Everyone Makes
Quick answer: People buy one large dry bag when they should buy two medium ones. A single 40L bag is harder to stow, harder to seal fully when underpacked, and puts every item you own behind one closure. Splitting the load into a 5L and a 20L is more useful in almost every scenario.
Here is what happens on the water. You need your phone at 10am, your lunch at noon, and your dry shirt at 4pm. With one big bag, every retrieval means opening the seal and exposing everything inside.
With two bags, the small one lives on you or clipped within reach, and the big one stays sealed until you need it. That is not a minor convenience. It is the difference between a bag that keeps things dry and a bag you keep opening in a splash zone.
There is a stowage argument too. Kayak bows and hulls are tapered. Two 10L bags slide into spaces a single 20L bag will not.
10L vs 20L: The Decision Most People Are Actually Making
Quick answer: Choose 10L if you are carrying personal items plus one soft layer for a half day. Choose 20L if you need a full change of clothes, food, and a jacket, or if you are packing for two people. When genuinely torn, take the 20L, since an underfilled dry bag still seals fine.
This is the real fork in the road, and the answer depends on one question: are you bringing a change of clothes?
A 10L bag handles a towel, a t-shirt, and pocket contents. Add real shorts, a jacket, lunch, and a camera and you are past its limit fast.
A 20L handles that comfortably, and it is the size most people end up using 80% of the time. It is also large enough to be a shared bag for two people on a day trip.
One point in favor of going up rather than down: a roll-top bag needs air pushed out and several folds to seal, so an underpacked large bag works fine, while an overpacked small one cannot close properly and leaks at the seam.
Size Doesn't Tell You If It Survives Going Under
Quick answer: Liters describe capacity, not waterproofing. Many roll-top bags are splash and brief-dunk rated, not submersible. Check for an IP rating: IPX7 means immersion to one meter for 30 minutes, and IPX8 means deeper than that.
This is where size charts mislead people. A 20L bag and another 20L bag can behave completely differently when a wave breaks over the deck.
Paddling Magazine draws the line clearly. Standard roll-tops offer protection "against splashes and brief dunkings," while only specific models are described as fully submersible.
The measurable version is the IP rating. IPX7 gear is tested by immersion in up to one meter of water for 30 minutes, while IPX8 is tested deeper than one meter. Our waterproof rating guide walks through how those levels translate to real use.
The second overlooked spec is buoyancy. A sealed bag with air in it floats. A stuffed bag full of dense gear may not. If losing the contents would ruin the trip, a bag designed to float on the surface matters more than an extra five liters of space.
Buoyancy is worth taking seriously for a reason beyond gear. The National Park Service notes that drowning is the second leading cause of unintentional deaths reported in national parks. Anything that keeps you from diving after a sinking bag is doing real work.
Sizing by Activity
Swimming, tubing, and the beach. 5L, or better yet, no bag at all for your phone. A sealed waterproof pocket built into your shorts means the thing you most want protected never leaves your body. We ran that test ourselves in our swim shorts phone experiment.
Kayaking and paddleboarding. 5L on deck plus 10L or 20L in the hull. Small bag for what you need, large bag for what you need dry at the end.
Boating and fishing. 20L minimum. You are carrying food, layers, and electronics, and a boat deck stays wet all day.
Hunting. 25L and up, because decoy bags, calls, layers, and shells add volume fast. Scent control adds a second requirement, which is why sealed hunting dry bags and blind bags are built differently than paddling bags.
Camping and overnight paddling. 30L to 40L for sleep gear, plus a 10L for clothes. Splitting by category makes finding things at dusk much easier.
Closure Type Changes What Size You Need
Quick answer: Roll-tops lose usable capacity to the closure, typically several inches of the bag height, so a 20L roll-top holds noticeably less than 20L of gear. A bag that seals without rolling keeps more of its stated volume available.
This is the specification hiding behind every sizing chart. Roll-top bags seal by rolling the top over itself several times, then buckling the ends together.
Those rolls consume bag. Pack a 20L roll-top to the brim and you cannot close it safely, because you no longer have the material to fold.
That is why we build around a magnetic auto-sealing closure instead. Nothing to roll means the stated volume is closer to the usable volume, and there is no technique to get wrong at 6am in the dark. We wrote the full comparison in auto-sealing versus roll-top dry bags.
If you are still deciding, start with the two-bag setup: something small and sealed for your phone and wallet, and a 20L for the rest of the day. Browse our floating dry bags and match the size to the load you actually carry, not the trip you might take someday.
Frequently Asked Questions
What fits in a 5 liter dry bag?
A 5L dry bag holds a phone, wallet, keys, sunglasses, a small snack, and a rolled t-shirt with room to spare. It will not hold a towel plus a change of clothes. Think of it as a sealed pocket rather than a pack, and keep it clipped within reach rather than stowed.
Which dry bag is better, a 20L or a 30L?
Choose 20L for day trips with a change of clothes, food, and a jacket. Choose 30L when you are carrying sleep gear or packing for two people. Paddling Magazine puts 16 to 30L in the sleeping bag and pad range, so 30L only earns its bulk on overnight trips.
How much can I fit in a 20L dry bag?
A 20L dry bag holds a full change of clothes, a towel, lunch, a light jacket, and a camera. Remember that a roll-top closure eats several inches of height, so plan on packing closer to 15L of gear if you want a proper seal with several folds.
What size dry bag should I use for a sleeping bag?
Most compressed sleeping bags fit a 16L to 30L dry bag, with 20L covering a typical three-season bag. If you are storing a bag and a sleeping pad together, size up to 30L. Do not overpack it, since a roll-top needs slack at the top to seal.
Sources
- Paddling Magazine, Best Dry Bags: https://paddlingmag.com/gear/accessories/bags-boxes-cases-packs/best-drybag/
- Keystone Compliance, IPX7 and IPX8 Water Immersion Testing: https://keystonecompliance.com/ipx7-ipx8-water-immersion/
- National Park Service, Stay Afloat: Always Wear a Life Jacket: https://www.nps.gov/articles/life-jacket-wear.htm
