Your total free cabin space: personal item plus carry-on, ranked by airline

Short answer: add the carry-on to the personal item and the free cabin allowance runs from about 69 L (European legacy) to roughly 80 L (US legacy). European low-cost carriers are the outlier: their free allowance is only the under-seat box, because the carry-on is sold separately. A free personal item that fits every sizer is worth the most exactly where the free total is smallest.

Free space is two items, not one

The "personal item" is only half of what your fare includes. We added a representative carry-on to each personal-item allowance to show the real free total you can board with.

The paradox of budget fares

On a European low-cost ticket the free total collapses to the under-seat box, because the carry-on is the upsell. That is precisely why a personal item that fits every sizer — for free, with no priority purchase — is more valuable on Ryanair than on Lufthansa. You are not "saving" the carry-on; you are avoiding having to buy it.

Where the 25 × 17 × 14 cm bag sits

At 5.95 L it is a small slice of any free total, which is the point: it is the bag you keep with you, not the one you stow. Its job is to clear the sizer on the strictest carrier so you never have to gate-check or upsize. The carry-on does the heavy lifting; this bag does the guaranteed-clear lifting.

Should you buy the Jelkin 25 for this?

The free cabin total runs 69–80 L on legacy fares but collapses to the under-seat box on low-cost ones — which is precisely where a guaranteed-compliant personal item is worth the most. The Jelkin 25 is a small slice of any total; its job is to be the slice that never gets questioned. Buy it as insurance against a fee, not as extra capacity.

How to check this yourself before you fly

1. Establish what your ticket includes free. On low-cost fares the carry-on is the upsell, not a given.
2. Treat the personal item as the guaranteed-free item and the carry-on as the paid-or-bundled one.
3. Measure the personal item against the strictest carrier you fly, not the most generous.
4. If your free total is only the under-seat box, spend the budget on a bag that clears every sizer rather than on priority boarding.

Keep reading:

• airline personal item size checker — all 19 carriers side by side
• one-centimetre depth cliff — why 15 cm decides six airlines
• the 25 cm bag that fits every sizer — length-vs-depth end to end
• why external dimensions lie about capacity — how we measure bags
• Jelkin 25 — the 25 × 17 × 14 cm bag measured on this page