Every other checker asks for dimensions you have never measured. This one starts from the airlines you actually fly and gives you the largest bag that clears all of them.
Every other checker asks for dimensions you have not measured. This one starts from the airlines you actually fly and works out the largest bag that clears all of them.
The right carry-on is not the biggest one that fits your usual airline. It is the biggest one that fits every airline you use, because the one time it does not is the time it costs you a gate check fee and your laptop goes into the hold.
Name the carriers you fly and the answer is governed by the strictest of them on each dimension — which is often three different airlines setting the three numbers.
Retail listings quote the case body. Add the wheels, the feet, the handle housing and the expansion gusset and a bag advertised as cabin-sized is frequently an inch over on two dimensions. If you are buying online, look for a listing that gives external dimensions including wheels, and if it does not, assume the worst.
If your list includes a European budget carrier, the number that comes back will be small — small enough that the honest conclusion is sometimes two bags rather than one compromise bag. That is a legitimate answer and we would rather give it to you than round it in your favour.