How Big Is a 20 Liter Dry Bag? | Size Facts That Matter

A 20 liter dry bag is a medium day-use size, but its physical dimensions vary by brand, typically measuring around 10 to 26 inches in one direction.

For the full breakdown, see our best 20 Liter Dry Bag guide.

Whether a 20 liter dry bag fits your day trip comes down to more than the number on the label. Capacity is standardized; physical size is not. One Sea to Summit model lists open dimensions of 11 x 7 x 24 inches, while another from the same brand measures 10.4 x 9.6 x 18.9 inches. That difference changes how it packs into a kayak hatch or backpack.

The good news: you don’t need to guess. The table below shows real measurements from current listings, and the sections after it explain what those numbers mean for the gear you actually carry.

What Does 20 Liters Actually Hold?

Think a change of clothes, a puffy jacket, lunch, and a small first-aid kit, all compressed into the bag’s main body.

Retailers typically frame a 20 L dry bag as suited for day-trip gear, small tents, or paddle-sport accessories. It is a middle-ground size: too small for multi-day camp loads, but far more useful than a 5 or 10 liter stuff sack for carrying soft goods you want to keep dry. If you’re comparing options for your next outing, our roundup of the best 20 liter dry bags tests how each model handles real-world packing.

Why Same Size Doesn’t Mean Same Shape

Brands build 20 L bags in different proportions. A tall, narrow tube packs differently than a short, wide duffel-style bag, even when both hold exactly 20 liters. Compare the numbers side by side.

Notice Sea to Summit’s own two models barely overlap in footprint. The Big River is a compact, nearly squared roll; the Lightweight version runs longer and thinner. The 5.11 stands tallest of the three, closer to a stuff sack in proportions. All three carry the same 20 L rating.

Open, Packed, and Rolled Sizes Differ

The dimensions printed on a listing are open measurements, taken before you roll the closure and cinch the buckles. Once you roll the top down three or four times to seal it, the bag gets shorter.

That distinction matters more than any single number. Quoted volume assumes the roll-top is closed properly, which compresses the empty space at the neck. A partially rolled bag still holds 20 liters, but it won’t fit where a fully rolled one does. Measure your storage spot against the open dimensions and expect the bag to shrink a few inches in height once sealed.

Shape also affects how much fits. Dry bags compress soft gear like clothing and sleeping bags efficiently. Hard-sided items—a camp stove, a water filter, a rigid lunch box—leave awkward air pockets that waste capacity, so a 20 L bag often holds fewer rigid objects than you’d expect from the math. Manufacturers describe these bags for water-resistant storage, not as flotation devices or fully submersible containers unless the label says otherwise. Keep the opening above water and the seal tight for best results.

How to Estimate the Right Size for Your Trip

Match the bag to your gear, not the other way around. A 20 L works well for a day paddle, a summit hike with extra layers, or a quick overnight where you pack light. For canoe camping with a full tent and sleeping bag, step up to 30 or 35 liters.

If you already own a 10 L bag that’s too small, a 20 L roughly doubles your space. If you’re moving down from a 35 L, expect to cut your load by about a third. Don’t rely on dimensions alone—a 20 L bag is defined by its volume, not its inches. When a specific model’s numbers look tight, compare its measurements against your pack’s main compartment before you buy. The internal link provides a practical starting point for comparing options side by side. Good luck out there, and pack the seal tight.