The official rule
Ryanair states that one small personal bag measuring 40 × 30 × 20 cm is included with all passenger fares. It must fit under the seat in front of you. If you buy Priority & 2 Cabin Bags, you can add a 10 kg cabin bag measuring up to 55 × 40 × 20 cm for the overhead locker.
Should you buy a bag exactly 40 × 30 × 20?
Not necessarily. A rigid or heavily structured bag built exactly to the published limit leaves less margin if the manufacturer’s measurements are optimistic, a handle protrudes or you pack it to capacity. With a soft bag, a few centimetres of spare room can make travel less stressful, especially across several airlines.
How many litres is that in reality?
A perfect 40 × 30 × 20 cm rectangular box has a theoretical volume of 24 litres. Real bags never use all of that space: seams, rounded corners, back padding, zips and pockets reduce usable capacity. Two bags sold as 20–24 litres can therefore have very different external dimensions.
Depth is often the problem
A soft backpack can look compact when empty and become too deep once packed. Front pockets, shoes or a rolled jacket can push the outer face forward quickly. To remain near 20 cm, it helps to spread volume flat and avoid overstuffing external pockets.
What we would check before buying
We prioritise verifiable external dimensions, sensible empty weight, useful access, compression straps and a shape that remains stable when packed. A laptop compartment can be valuable, but on some bags it also consumes several centimetres of depth.
What if the bag is slightly too big?
We would not base a recommendation on the assumption that an oversized bag will be ignored. Enforcement can vary by airport and flight, but the published dimensions remain the official allowance. If your packed bag is larger, treat that as a possible extra-charge risk.
Our practical recommendation
For travellers who want less stress, we would aim for a bag that genuinely measures around 38–40 cm high, 28–30 cm wide and 18–20 cm deep when packed. That is not a new Ryanair rule; it is simply the comfort margin we prefer over using every published millimetre.
Always check before travel
Baggage policies can change. We date this page and keep the official Ryanair source linked below. Check your booking and the current airline policy again shortly before departure, especially if the ticket was bought well in advance.
How we work
We verify information, cite sources where relevant and date our updates. Prices, availability and rules that may change should always be checked again with the relevant source or service.
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