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Dry Bag Size for Laptop and Documents

Measure the device before you measure the bag

Screen size is a diagonal number and almost useless for packing. A machine sold as 14-inch carries a 35.6 cm diagonal, but the closed body is typically 31 to 32 cm wide, 22 to 23 cm deep and 15 to 18 mm thick. Put that same machine into a padded sleeve and it becomes about 34 x 25 x 28 mm and gains 180 to 260 g. Measure the closed device with a tape, add the sleeve, then add 20 mm in each direction for the fabric walls and the fold line.

Two devices with the same screen diagonal can differ by 3 cm in width, and that difference is the whole decision. A 16-inch mobile workstation runs 36 cm wide and 26 mm thick and will not lie flat in anything marketed as 15L. Carry three numbers on a card when you shop — width, depth, thickness — and treat litres as the last figure you look at rather than the first.

Why litres mislead and flat panels decide

A litre is 1,000 cubic centimetres and says nothing about shape. A 20L roll-top that is 26 cm in diameter and 48 cm tall will accept a 34 cm wide panel only on the diagonal, which loads the corners, prints a permanent crease into the film and leaves the closure fighting the contents. What actually matters is the usable flat panel: the widest rectangle the bag takes with the closure still able to make three full folds. Where a spec sheet gives no panel dimension, assume the litre figure describes clothing, not electronics.

Roll-top closures eat height before they seal. Three folds remove 6 to 9 cm from the top of the bag depending on fabric weight, and the moulded stiffener at the mouth takes another 1.5 cm. A bag advertised at 48 cm tall therefore offers roughly 38 to 40 cm of packing height. Subtract the 20 mm of clearance a padded sleeve wants at the base seam and the practical floor for a 14-inch laptop is a bag sold at 45 cm or taller.

Roll-top, tote or backpack for a device load

A roll-top dry bag gives the best seal per gram and the fastest open-and-close cycle, but it has no internal organisation at all. A laptop inside a roll-top is only as safe as the sleeve you put around it first. If your day runs from a wet dock or a rain-soaked street to a desk, the roll-top plus a rigid sleeve is the most reliable combination and the easiest to re-pack in a hurry.

A waterproof tote with a built-in padded sleeve solves the organisation problem: the device slides into a dedicated panel, documents stay flat against the back wall, and the mouth still closes against rain. A TPU waterproof backpack spreads the same 2.4 kg across two shoulders, which matters above about 20 minutes of walking. Choose the tote for short urban hops and the backpack for anything over a kilometre on foot.

Padding depth and what a drop test really shows

A 1.4 kg laptop dropped from 0.8 m reaches about 4 m/s and stops in a few millimetres when a corner lands on concrete. Thin neoprene sleeves look tidy and do almost nothing: a 2 mm layer compresses fully in the first 3 ms and passes the remaining shock straight into the corner of the chassis. A 5 mm closed-cell foam or EVA layer spreads the same impact over roughly 25 ms, which is the difference between a dented corner and a cracked board.

Corner protection matters more than face protection, because corners take the hit in almost every real drop. Look for a sleeve with reinforced corners and a lip that stands 5 mm above the device edge, then check that the bag itself has a welded base rather than a folded one; a welded base spreads point loads from gravel, kerbs and boat decks. Pair that with the carrying advice in our laptop protection guide if the device travels on the water.

Documents, folders and the volume nobody counts

Paper is heavier and bulkier than people expect. An A4 sheet is 210 x 297 mm under ISO 216; a ream of 500 sheets of 80 gsm paper weighs 2.5 kg and stacks 52 mm high, so 200 sheets in a folder is about 1.0 kg and 21 mm. Letter-size paper is 216 x 279 mm and slightly narrower, which means a folder cut for A4 will swallow a letter folder but not always the reverse.

Paper also fails differently from electronics. A splash that a laptop would survive destroys a printed contract within seconds, because capillary action pulls water along the sheet edges and the ink runs before the page dries. Carry paperwork in a rigid folder or a slim polypropylene wallet inside the main bag, keep it against the back panel away from the closure, and never let a wet bottle share the same compartment.

Condensation and humidity around a warm device

A dry bag that seals well also seals humidity in. Pack a laptop that has just come out of a 26 °C room, close the bag, then carry it into a 14 °C evening or an air-conditioned terminal at 45% relative humidity, and the trapped air will cross its dew point inside the bag. In practice this shows up as a fine film on the inside of the film wall and, worse, on a cold device screen.

Two habits remove almost all of it. Let the device cool to near ambient before it goes into the bag, and keep a 20 g silica sachet in the same compartment, recharged in a 120 °C oven for an hour every month. If you are travelling between climates with big temperature swings, open the bag for five minutes on arrival rather than pulling a cold machine straight out into humid air.

Rain, splash or immersion: the rating a device needs

Device loads see two very different exposures. A commute is a rain event: driven water at 5 to 12 m/s from the side, plus the soak you get standing still at a crossing. That is an IPX4 to IPX6 problem. A bag sitting in an open boat or on a paddleboard is an immersion event, which is IPX7. The IEC defines these grades in IEC 60529, so a credible spec sheet names the standard instead of inventing adjectives.

For a laptop, the cheapest insurance is redundancy rather than a higher rating: keep the device in a padded sleeve inside a welded IPX6 bag, and put the passport and phone in a 2L inner pouch. Two independent barriers cost 60 g and remove the single-point failure that ruins a working trip. Full rating detail is in our IPX ratings guide.

Airport security and handling with a loaded bag

Security lanes reward bags that open completely and quickly. A roll-top with three folds is open in about four seconds and lays flat on a tray, which is faster than a long waterproof zip and far less likely to snag. A tote with a separate sleeve panel lets you slide the device out one-handed while the paperwork stays in place, which is worth a lot when the tray queue is moving.

Cabin weight limits are the other half of the problem: a 2.4 kg device load plus a 700 g bag is 3.1 kg before you add a bottle and a jacket, and many regional carriers cap a personal item at 5 kg. Weigh the packed bag at home on kitchen scales, then decide what moves to the hold baggage. Our notes on airport security with dry bags and checking a dry bag on a plane cover the edge cases.

Weight and carry comfort across a working day

Load weight is the variable people underestimate. A 14-inch laptop at 1.6 kg, a 400 g charger, a 500 g folder, a 300 ml bottle and a light shell come to about 2.8 kg before the bag itself. Carry that in one hand in a tote for 800 m and the forearm and trapezius do the work; carry it in a harness with 38 mm padded straps and a sternum strap and the same load is unremarkable over two kilometres.

Strap width is not cosmetic. A 25 mm webbing strap carrying 3 kg puts roughly 12 kPa under the strap contact area and starts to feel sharp after 15 minutes; the same load on a 38 mm padded strap sits near 5 kPa and is comfortable for an hour. If you expect to carry a laptop daily, buy the harness and accept 180 g of extra bag weight.

Colour, finish and the office test

A bag that goes from a boat to a meeting has to survive two kinds of judgement: abrasion and dress code. Black and charcoal hide scuffing and read as neutral in almost every workplace; mint, pink and camo are excellent on the water and conspicuous in a client lobby. Mid-grey is the compromise that hides salt marks without looking technical.

Finish matters as much as colour. A matte TPU face scuffs to a dull patch that can be wiped; a glossy PVC face scuffs to a white mark that cannot. If the bag will spend its life on an office floor, choose matte and add a reflective accent for the walk home; we cover the placement options in reflective accents for night use.

A repeatable pack order for laptop and paperwork

1. Slide the cooled device into the rigid sleeve with the corners seated, then check the lip stands proud of the chassis edge.
2. Stand the sleeved device against the back panel of the bag, hinge side down, so the spine takes the base load.
3. Lay the document folder flat in front of the sleeve, spine up, clear of the closure line by at least 3 cm.
4. Drop the charger and cables into a 2L pouch and wedge it beside the folder so nothing can slide to the mouth.
5. Press the air out, make three folds, clip the buckle, then lift the bag by the strap and listen for a hiss.

The order is deliberate. Devices go against the back panel because that is the side that stays flattest and takes the least abrasion when the bag is set down. Paper goes in front because it must stay flat. Loose cables go into a pouch because a bare USB-C plug left in the bottom of a bag will print a permanent dent into both the folder and the device lid over a season of commuting.

Care routine for a bag that carries electronics

Electronics introduce a contaminant that outdoor kit does not: conductive debris. Crumbs, staple fragments and paperclip ends find their way into the bottom seam and abrade the weld from the inside. Empty the bag fully once a week, wipe the interior with a damp microfibre cloth, and check the base weld line with a fingertip for grit before it works into the film.

Salt and city grime behave the same way on hardware. Rinse buckles and cam levers with fresh water, work them through their full travel while wet, then dry in shade with the mouth open. Never machine wash a bag that has carried a laptop; the twisting loads the welded seams in a direction they were never tested for. Step-by-step detail is in our roll-top cleaning guide.

Sizing checklist before you commit

• Write down the sleeved device footprint: width, depth and thickness, measured closed.
• Demand a stated flat panel from the bag spec, not just a litre figure.
• Confirm the bag still makes three folds with the device inside; check the height after folding, not before.
• Match padding to risk: 5 mm EVA for daily carry, 2 mm neoprene only for scratch protection.
• Budget the weight: keep the whole load under 4 kg if a shoulder strap is doing the work.
• Plan a second barrier for passport and phone: a 2L inner pouch inside the main bag.
• Choose matte, neutral finishes if the bag splits its life between water and the office.
• Compare the shortlist against the full product line before you settle on one size.

If you are specifying bags for a field team, a rental fleet or a retail range, the same checklist becomes a buying brief: panel dimension, padding depth, closure height after folding, carry weight and the test standard behind the waterproof claim. Our production partner has built waterproof bags since 2014 in an SGS-verified 4,950 m2 facility with 137 staff and seven production lines, working to a 500-piece minimum with sampling in 6 to 10 working days and bulk in 35 to 50 days.

Two neighbouring decisions tend to follow this one. If the load also includes a camera body and lenses, the panel maths changes shape rather than size and the camera kit sizing guide is the better reference. If you are simply deciding between two sizes on the same platform, read dry bag volume versus backpack volume first, because a 20L dry bag and a 20L backpack do not hold the same shaped load.