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What Fits in a 30L Dry Bag

What 30 litres means once the top is rolled

The volume printed on a roll-top bag is measured to the brim, before a single fold is made. Rolling the mouth three times, which is what keeps water out during a capsize, consumes the top 9 to 11 cm of a typical 55 cm tall body. On a 30L bag with a 28 cm mouth that works out at close to 4 litres of the labelled capacity, so the bag you bought as a 30L delivers 25 to 26 litres of usable space.

That gap is geometry rather than a defect. The folds have to lie against each other with enough contact pressure to break the water path, and the film needs a little slack to make the bend without taking a permanent crease. Fill the bag to the brim and you can still roll it, but the folds will be shallow, the buckle will sit under tension, and the closure will weep the first time a wave lands on it.

Plan on 85% fill. For a 30L bag that means around 22 litres of gear and 3 litres of air, a combination that seals properly and leaves a soft outer surface that squeezes into a hatch. Pack 26 litres and you will fight the closure on every trip; pack 18 litres and the bag slumps, rolls on a deck and takes up more room than its contents justify.

The 30L load list, item by item

Volume planning only works with real objects in front of you. The table below uses a three-season canoe or bikepacking load packed the way people actually pack it: sleeping bag inside a compression sack, clothing rolled rather than folded, food stripped of retail packaging. The cumulative column is the one to watch, because it tells you the exact item at which the bag stops closing.

The cumulative column is where most packing plans break. Sleep system and clothing together reach 19.1 litres, which feels comfortable. Add the stove kit and three days of food and you cross 25 litres, at which point the wash kit and the electronics pouch are the items that have to travel somewhere else, either in a second small roll-top or in a jacket pocket.

Swap the down bag for a synthetic winter bag rated to -5 °C and the sleep system grows from 11.5 to about 16 litres. The whole load then lands near 31 litres, and no amount of rolling discipline will close that into a 30L bag with three folds. That is the honest reason 30L is a three-season size and cold-weather trips move up to 40L.

Sleeping systems: whether bag and pad fit together

A down bag rated to 0 °C compresses to roughly 8 litres in a decent compression sack; the same rating in synthetic fibre takes 11 to 12 litres and carries 400 g more. Add an inflatable pad rolled to 3.5 litres and the sleep system occupies 11.5 to 16 litres, which is between 44% and 62% of the usable volume of a 30L bag.

Compressing the bag separately rather than stuffing it loose into the dry bag saves 2 to 3 litres, because a compression sack forces the loft into a cylinder that matches the shape of the bag. The trade-off is one more thing to open in the rain, and a compression sack that is not waterproof, so the dry bag still has to do the sealing work.

If a pad travels with you, strap it outside rather than inside. Four litres of pad inside the bag steals space from clothing and food; lashed to an external point it costs nothing and dries faster after a wet night. Welded D-rings on a TPU shell take that strap without deforming, which is the single hardware detail worth checking on a specification sheet.

Clothing volume by season

Clothing is the category that changes most with the calendar and the one most people underestimate. In a shoulder-season load, four layers come to about 8 litres and 1.8 kg. In deep winter, six layers reach 13 litres and 3 kg, which on its own fills half the usable volume of a 30L bag before any sleep system is added.

What separates summer from shoulder season is smaller than it feels: 4.5 litres against 8 litres, the difference of one insulated jacket and a pair of long bottoms. That is why the same 30L bag feels generous in August and tight in October on an identical route with an identical sleep system.

One habit pays off on every trip regardless of season. Keep a complete dry layer set sealed in its own small bag inside the main load: a 2L roll-top swallows a base layer, socks and a neck gaiter in about 1.6 litres. Even if the main closure is compromised during a swim, you still have something dry to change into at camp.

Food and cooking kit in a 30L load

Dry food averages 0.6 kg per litre once retail packaging is stripped: rice, pasta, oats and dehydrated meals all sit close to that figure, while anything with fat or sauce is heavier per litre. Three days of food for one person therefore weighs about 2.1 kg and occupies 3.4 litres. Seven days weighs 4.9 kg and occupies close to 8 litres.

• Stove, pot, mug and a 230 g fuel canister: 2.4 L, 780 g, packed as one nested unit.
• Three days of meals at 0.6 kg per litre: 3.4 L, 2.10 kg, decanted into soft pouches.
• Coffee, tea and electrolyte tablets: 0.4 L, 250 g, in the lid area where they stay dry.
• Cold-soak alternative with no stove: 0.0 L, 0 g, adds roughly one extra day of food space.

The stove kit is the easiest 2.4 litres to delete. A cold-soak plan, where meals rehydrate in a sealed pouch while you walk or paddle, removes the stove, the pot and the fuel, saving 780 g and freeing enough volume for a fourth day of food. In warm weather that trade is almost always worth making.

Wherever the food ends up, pack it low and central. A 30L bag with 2.6 kg of food at the bottom carries like a far smaller load, because the mass sits against your back or low in the hull. The same weight at the top swings with every step and turns a shoulder carry unpleasant after the first kilometre.

What a full 30L load actually weighs

Volume is what stops you closing the bag; weight decides whether you enjoy carrying it. The breakdown below is the same three-season load from the item list, grouped into five categories so the shares add up. Food and cooking is the largest single block by weight, and sleep system is the largest by volume, which is the pattern behind almost every overloaded 30L bag.

The total is 25.8 litres and 6.8 kg, which is close to the realistic ceiling for a 30L roll-top carried on one strap. Past 7 kg the bag needs a harness: a plain roll-top with a single shoulder strap is tolerable for 400 m from the car park and genuinely uncomfortable at 2 km, because the load swings with no load lifters to steady it.

If the load is going to be carried on your back rather than stowed in a boat, look at a welded TPU waterproof backpack instead of a plain sack. Thirty litres with a padded harness and a sternum strap changes how far you can walk with the same weight, and the backpack versus duffel comparison sets out the format trade-offs in numbers.

Two nights or a full week: where 30L runs out

For a two-night trip the 30L is the comfortable choice. Sleep system, four clothing layers, three days of food, a stove kit and a wash pouch come to about 25 litres with a little slack, and there is room left over for a compact camera, a paperback or a folding stool.

Stretch the same trip to five days and food alone reaches 6 litres, which pushes the load past 28 litres. The bag will still close at that point, but only with two folds, and a two-fold closure is splash-proof rather than immersion-proof. That is the moment a 30L stops being the right tool for the job.

The usual fix is a split rather than an upgrade: a 30L for clothing and sleep system plus a separate 10L food bag, or a move to 40L with a small second bag for electronics and documents. Our weekend trip sizing notes cover the short end of that range and the seven-day expedition guide covers the long end; both start from the same measured item list.

Mouth width, body height and how geometry changes packing

Two 30L bags can pack very differently. A wide-mouth design with a 30 cm opening swallows a sleeping bag in one motion; a tall, narrow 26 cm mouth is slower to load but slides into a sea kayak hatch that the wider bag will never enter. Height matters as much: a 60 cm tall body lashes neatly across a rack, while a squat 45 cm one sits better in a canoe.

Format matters as much as dimensions. A roll-top sack packs from the top only, so whatever went in first stays buried until everything else comes out. A 30L dry duffel opens along its length and lets you reach the bottom third without unpacking, which is worth a great deal when you need one item in the rain.

Whichever format you choose, the capacity arithmetic is identical, and it is worth understanding before comparing sizes between brands. Our explainer on roll-top capacity loss sets out what each fold costs in litres, and the capacity guide from 2L to 90L places 30L inside a whole size range.

Situations where 30L is the wrong answer

The decision rule between 20L and 30L comes down to one measurement. Compress your sleep system and measure it: under 11 litres and a 20L bag will take everything else; over 12 litres and you need the 30L even if the rest of your kit is minimal.

Our 20L versus 30L comparison walks through that rule with photographed loads, and the 20L load list gives you the smaller bag numbers to compare against line by line.

A packing order worth repeating

1. Put the food bag and the stove kit in first; they are the heaviest and least compressible items.
2. Add the sleeping bag in its compression sack and press it into the corners.
3. Fill the gaps around the sleep system with rolled clothing, not folded clothing.
4. Slide the wash kit and first-aid pouch down one side rather than on top.
5. Add electronics in a small inner roll-top and seat it near the mouth.
6. Press the air out with a forearm before making the first fold.
7. Roll three times, clip the buckle, then squeeze the bag and listen for a hiss.

Repeating the same order every trip is not fussiness. It makes the load predictable: you learn what 22 litres looks like in your own bag, and you notice a missing item at the trailhead rather than at camp in the dark.

Air, closure and the squeeze test

Air is the variable that decides whether a 30L bag seals and whether it floats. Press the load down with a forearm before the first fold so the film closes on itself rather than on a trapped pocket, then roll three times and pull the buckle tight enough that the folds cannot unwind.

A purge valve earns its place at this size. Compressing 25 litres by hand is slow work, and a valve lets you push the last of the air out after the bag is closed so it lies flat in a hatch instead of ballooning against the hull.

Finish with a squeeze test every time. Roll the bag, squeeze it firmly and listen. A bag that hisses has a fold problem rather than a fabric problem, and it will take water the first time a breaking wave lands squarely on the closure.

30L across four activities

Weight is the variable that changes least and matters most: every one of those loads sits between 5 and 8 kg. Under 4 kg, a 20L is simply more pleasant to carry; over 9 kg, look at a 40L with a harness rather than fighting a 30L that is stuffed past its design point.

Spec checklist before you commit to 30L

• Weigh and measure your sleep system compressed; that one number decides 20L, 30L or 40L.
• Plan food at 0.6 kg and 1.1 litres per day, then multiply by the number of days.
• Choose a mouth width that fits both your sleeping bag and your hatch, rack or sizer.
• Confirm the film: 0.5 mm TPU for abrasion, 0.3 mm only if every gram matters.
• Check lash points: welded D-rings rather than sewn webbing for anything load-bearing.
• Ask which standard the waterproof claim was tested to, not which adjective was used.
• Compare sizes across the product line and the capacity guide before ordering.
• Read how capacity is measured so you compare like with like.

For clubs, rental fleets and retail ranges this checklist becomes the purchasing brief: volume, film thickness, mouth geometry, lash points and test standard are the five lines that decide whether a 30L survives a full season. We have produced waterproof bags since 2014 in an SGS-verified 4,950 m2 facility running 7 lines and 149 machines, with a 200,000-piece monthly capacity, a 500-piece minimum, sampling in 6 to 10 working days and bulk in 35 to 50 days, FOB Xiamen.

Two standards bodies sit behind most of the testing language you will meet on a specification sheet. The ISO publishes the waterproof and textile test families that independent laboratories work to, and ASTM publishes the coated-fabric methods used for abrasion and hydrostatic resistance. Ask for the standard number, not the marketing phrase.

Finally, respect the load in human terms. A 30L bag at 7 kg carried across a wet boat ramp is a genuine trip hazard for one person, and a split into two lighter bags is safer than a heroic single carry. Our roll-top range covers the sizes on either side of 30L so a club can standardise on one closure system.