Understanding Litre Capacity
Bag capacity is measured in litres, representing the volume of space inside the main compartment. This standardised measurement allows comparison across brands and styles. However, two bags of the same litre capacity can feel quite different depending on their shape, pocket arrangement, and opening style.
As a rough guide, each litre of capacity can hold approximately one kilogram of loosely packed clothing. A 40-litre duffle can theoretically hold 40kg of gear, though practical limits and weight restrictions typically mean you'll carry far less. Shape and access also matter: a wide-opening 40L duffle feels more spacious than a top-loading 40L backpack.
Size Categories Explained
Extra Small: 20-30 Litres
Best for: Day bags, personal items, minimalist gym-goers
These compact duffles carry the bare essentials: a change of clothes, small towel, toiletries, and phone. Popular as secondary bags for day trips or as personal items accompanying larger luggage. Some Australian commuters use this size for work lunches and gym gear for lunchtime workouts.
Typical contents: One outfit, toiletry kit, small towel, water bottle, phone and wallet
Small: 30-40 Litres
Best for: Regular gym use, day trips, one-night stays
The most popular size for dedicated gym bags. These duffles accommodate workout clothing, trainers, towels, and personal items without excessive bulk. They fit easily in gym lockers and remain comfortable to carry on public transport or while cycling. Also suitable for overnight trips where you pack light.
Typical contents: Two outfits, shoes, full-size towel, toiletries, water bottle, small electronics
Medium: 40-55 Litres
Best for: Weekend trips, extended gym sessions, carry-on travel
The versatile middle ground that handles most scenarios. Medium duffles suit weekenders who pack comfortably, gym-goers with extra equipment, and carry-on travellers on domestic Australian flights. This size offers enough room for three to four days of clothing while remaining manageable in overhead bins and hotel rooms.
Typical contents: Three to four outfits, two pairs of shoes, toiletries, laptop, jacket, travel accessories
Large: 55-70 Litres
Best for: Week-long travel, sports equipment, team players
Large duffles exceed most carry-on limits but remain practical for checked luggage or car travel. Athletes appreciate this size for carrying protective gear and multiple uniform sets. Week-long travellers can pack comprehensively without needing additional bags. These duffles often include wheels or convertible backpack straps for easier transport.
Typical contents: Full week of clothing, multiple shoes, sports equipment, toiletries, electronics, outerwear
Extra Large: 70-90 Litres
Best for: Extended travel, camping, seasonal relocations
Serious capacity for serious journeys. Extra-large duffles serve travellers on extended trips, students moving between university and home, and outdoor enthusiasts packing camping gear. The trade-off is significant size and weight when fully loaded. Wheels become essential at this capacity.
Typical contents: Two weeks of clothing, camping gear, multiple shoe pairs, full toiletry kit, electronics, books, outerwear
Expedition: 90+ Litres
Best for: Expeditions, seasonal workers, mountaineering, major relocations
The largest duffles available, designed for specific use cases rather than everyday travel. Expedition duffles suit mountaineers carrying extensive gear, seasonal workers relocating for months, and adventure travellers on extended journeys. These bags require careful packing to remain manageable and often serve as equipment transport rather than personal luggage.
Typical contents: Extended wardrobe, complete camping/climbing gear, seasonal equipment, work tools
Choosing the Right Size
Consider Your Primary Use
Your most frequent use case should drive your size selection. A daily gym-goer needs a 30-40L bag even if they occasionally travel, because the bag will be carried constantly. A frequent traveller benefits from 45-55L even if it feels excessive for gym use. Let your dominant activity guide the decision.
Think About Your Packing Style
Honest self-assessment helps here. If you consistently overpack or prefer outfit options, size up. If you're a minimalist who travels light, you might manage with smaller capacity than typical recommendations suggest. There's no shame in needing more space than someone else for the same trip length.
Account for Australian Conditions
Australian travel often involves variable climates. A weekend in Melbourne might require layers that a Brisbane trip wouldn't. If your travel spans different climate zones, additional capacity for temperature-variable clothing makes sense.
Airline Carry-On Considerations
If you want your duffle as carry-on luggage, size limits matter. Australian domestic airlines (Qantas, Virgin Australia, Jetstar) typically allow bags up to 56cm x 36cm x 23cm. Most duffles in the 35-45L range meet these requirements when not overpacked. Larger duffles will require checking unless they're exceptionally flexible and underfilled.
Remember that capacity claims can be optimistic. A "45L carry-on duffle" might technically fit overhead when empty but exceed dimensions when fully packed. Soft-sided duffles offer some flexibility, but don't assume you can stuff a maximum-capacity bag into minimum-space limits.
Weight Considerations
Capacity means nothing if you can't lift the bag. As a general rule, most people can comfortably carry 10-15kg for extended periods. Athletes and larger individuals may handle more; others may struggle with less. Consider not just what fits in the bag but what you can realistically transport.
The bag's own weight matters too. A heavy-duty 65L expedition duffle might weigh 2kg empty, while a lightweight version weighs 1kg. That difference matters significantly when you're near weight limits or carrying long distances.
Still Unsure About Size?
Our interactive quiz considers your specific needs and recommends the perfect duffle bag size for your lifestyle.
Take the QuizWhen One Size Isn't Enough
Many active Australians own multiple duffles for different purposes. A compact 35L for daily gym use doesn't serve week-long travel well, and a 65L travel duffle is excessive for the gym. Having the right tool for each job beats compromising with an ill-suited single bag.
If budget allows only one duffle, choose based on your most frequent need, acknowledging you'll occasionally wish for different capacity. Alternatively, select a versatile medium size (45-50L) that handles most situations adequately if not perfectly.
Compression features can also extend a bag's useful range. Duffles with compression straps or panels can shrink down when lightly packed, making a larger bag more practical for varied uses.