What is the Official Approved Carry on Bag size

Every airline has different size limitations for carry on. Check your specific airline. If you're flying more than one, you'll need what I call the lowest (highest??) common denominator sizing and sometimes that means piecing together one airline's stingy width limit with another airline's stingy weight limit.

There is no "official" size. Each airline can set their own, and change them at will. Foreign carriers set limits in centimeters not inches, so its not exact translation. Sometimes its the weight limit that catches you.

Most of the European airlines I looked at said a total measurement of 115cm - 21 x 14 x 9 is just under 112cm and the weight for economy is 10kg or 22 lbs 😲

As said above, you have to check the size-weight restrictions for all of the airlines you'll be flying and go with whichever required the smallest/lightest.

For instance, see this post today by someone who is flying a budget airline which only allows 5g of weight for free in a carryon. That's extreme but can happen:

https://community.ricksteves.com/travel-forum/general-europe/wow-air-66336f8d-4d3e-4559-ac74-fc8baa959322

Anyway, wheels count in an overall measurement, and you want to measure with the bag fully packed as bulging can exceed the limit.

WOW - I don't think I'll be WOWing any time soon. Only 1 carry-on at all - those baggage fees can add up quick!

Connecting flights between US East Coast/Canada and Europe (Via flights)

Carry-on luggage
Small carry-on bag 0-5 kg (0-11 lbs) Per guest, per via flight
1 piece per guest. Size: 56 x 45 x 25 cm with wheels and handles, max. 5 kg (11 lbs). (9) Included Included
Extra 7 kg (15 lbs) for a carry-on bag (8) Per guest, per via flight
Max. 12 kg (26 lbs). (You are only permitted one piece of carry-on luggage) $48.99 $67
Carry-on luggage Over permitted size: see check-in luggage.

Check-in luggage (hold luggage)
One bag, max.
20 kg (44 lbs) (5) Per guest, per via flight $67.99 $76
Two bags, max. 20 kg (44 lbs) each (5) Per guest, per via flight $135.98 $152
Three bags, max. 20 kg (44 lbs) each(5) Per guest, per via flight $203.97 $229
Overweight charge (6) Per kilo - max. 12 kg (26 lbs) extra per bag

$19

BTW - "allows 5g of weight" should read 5kg - I'm certain it was a typo

DOH! My bad: I mis-typed 5kg.
Disobedient fingers….

Yes - they all set their own and can change them anytime. We bought a personal size computer bag because it met both Air Canada and Brit Air standards for the smaller personal item - then BA made the dimensions smaller. And we got stuck with a lovely $70 Swiss Gear computer bag that we never used because we couldn't use it on BA when we went overseas last year.

BTW - I have a lovely unused Swiss Gear computer bag for sale! :)

Thank you so much everyone for responding. I knew that the US and Canadian airlines different but was under the impression that overseas airlines had one official size carry on. So I appreciate all of you taking time to respond.

At one time I looked at a lot of websites for foreign and domestic airlines that travelers commonly use and listed their carryon luggage size limits on a spreadsheet. At that time, I would say that most European airlines used 55cm x 40cm s 20cm (21-5/8" x 15-3/4" x 7-7/8") as a limit while most US airlines were using 22' x 14" x 9", A lot has changed since then. I see a lot of European airline adopting the 14" x 9" US standard (in cm, 36cm x 23cm), but retaining the 55cm length limit, which is a problem for US bags, which are often 22" long or longer, including wheels and handles. British Air added 1 cm to their length to make it 56cm or 22.05 inches.

As for weight, that varied a lot, from 5kg (11 lb) for some airlines to 12kg (26.4 lb) for another. US airlines don't seem to put a weight limit on it. You just have to be able to lift it yourself.

Consumer Report recently published a test they did on the actual size of luggage compared to the advertised size and found that 9 of 10 exceeded the manufacturer's advertised length and 8 of 10 exceeded the 22" length standard used my most US airlines.

What Lee said. Two years ago I was looking for a carry-on with wheels in Chicago that would meet Turkish Air's limits. I took a tape measure with me to go shopping. I also took a luggage scale. The limit was 55 cm (21.7"). Not one of the bags labeled 21" was within the 55 cm limit. And the bags that were labeled "light-weight" - well, let's just say my idea and theirs differ by a kilo or two!

The only reason I can see for Turkish Air's low limit is to speed up boarding. They are about the only airline that still gives two free checked bags, so it's not to make a few extra dollars.

As others imply, the critical measurement is the out-to-out dimension, not the interior dimension. 55 cm rounded up to 22 inches or rounded down to 21 inches isn't a big deal if the carry-on is a soft sided bag. It could be a no-go if it has a rigid frame and the checking device is a rigid box. Soft sided luggage can be compressed a bit and pushed in. A rigid bag with hard wheels on one end and a hard handle on the other will not go. The same applies to the overhead compartment. I've seen passengers having to load carry-on bags with length parallel to walkway instead of the required wheels in orientation because their bag is too long to close the door.

I should add that a RS 9-inch thick soft sided bag will fit a 20 cm checking frame if you don't pack to the max and use the cinching straps to get it under the 20 cm thickness. No rule that you need to pack a bag to the maximum although it's always tempting to add an extra pair of socks or shirt.

http://travel-made-simple.com/carry-on-size-chart/

Just sayin'.

Don't rely solely on that chart. I saw mistakes. Check directly with your airline.

Check your airlines because I checked mine and another and they are all different. Also Europeans airlines are different. So if you know check that as well.

Don't rely solely on that chart. I saw mistakes.

Lufthansa is 21-5/8 x 15-3/4 x 9 inches, not what the chart says. Weight is right, 17.6 lb.

My wife an I are flying to Rome via United in August 2016 and returning via Turkish Airlines. We will be following the Turkish rules for carry on which are little more restrictive; especially on weight. Turkish weight restriction is 8 kg or 17.637 lbs. We always pack and check our carry-on baggage with a luggage scale. I have see the foreign carriers check the weight of carry-on bags!