This is a very complicated problem as airlines differ. Everything follows in centimeters, it's Europe. Often the personal item comes with the purchase of an add on and can't be purchased on its own:
Code:
Name |Carry on|Personal|Personal requirement
Ryanair |55 40 20|35 20 20|Free
easyJet |56 45 25|45 36 20|Better Seat
Air Berlin |55 40 23|40 30 10|Free
Wizzair |42 32 25|40 30 18|Priority boarding
Wizzair paid|56 45 25|40 30 18|Priority boarding
Norwegian |55 40 23|33 25 20|Free
Some notes
- Wizzair is weird: it requires payment for a sane sized carry on. That payment does not trigger a personal item, though. It is super weird and widely unknown that the handles and wheel do not count into the allowance and just about every site claims the opposite despite these news from 2014 Christmas:
https://book.wizzair.com/en-GB/about_us/news/wizzhu048
we have asked passenger handling partners across our entire network of 104 airports, to apply common sense and reasonable flexibility when screening baggage sizes, and to allow cabin baggage on board even when handles and wheels protrude out of baggage sizers.
You can also compare the 2013 and the 2016 General Conditions Of Carriage to observe the "dimensions include wheels, handles and side pockets" phrase has been reduced to "include the side pockets". Yuuuuup.
- More expensive tickets on Norwegian increase the max combined weight but not the baggage size.
- easyJet personal item is huge. If you buy something this big it won't be accepted as a second bag anywhere else. It is close to the primary free Wizzair though.
- It is now visible why European luggage sites care about conformity with Ryanair: it's the largest low cost airline there and if it's that small, it'll work everywhere although paid on Wizzair.
- The primary baggage size (and the weight!) is often enforced. The personal item might be eyeballed only. Remember they see hundreds of bags daily and know this well.
- I have seen staff at the gate armed with measuring tape. Do not go over! They have every incentive possible to force a check in. Mercy is not part of their business model.
With this much variation, duffels and backpacks are my preference, something pliable. If you buy a rolling suitcase, well, you nailed down two dimensions out of the three -- that better be 55cm x 40cm. The U119CX for example is 48.5 cm x 35.5 cm which is below. It is 23cm deep though at which point you need to make sure not to make it bulge lest someone does challenge it -- the Ryanair sizer is 212mm deep (it is not just gate staff who is armed with a measuring tape
the other two dimensions are 412mm and then about 580mm but it has two rods on the bottom so it's not really more than 550mm) so they might.
So there you go. Ask if you have more questions.