Carry On Baggage Dimensions

We flew on AF in 2023 in Premium Economy. My recollection is that the carry-on dimensions were the same as regular economy. Business class, I don't know. However, I plan for the smallest dimensions and take a bag for that. Why get a bag that is a bit bigger and qualifies for one airline and take a chance with possible flights on a different airline? The dimension totals you mention go from 114 to 118, not a great difference in what you can pack. Suppose you go with the bigger bag and your flights/airlines change? Will you have to gate-check?

(Personally, we are now of an age that we check our carry-on size bags because it is too difficult to put our bags in the overhead bin and get them down. Even having bags lost for 4 days a few years back on a trip to Kenya, we still enjoy the freedom not dealing with carry-on affords. Of course, we are in our 80's and our traveling style is not what it was 20 years ago.)

"I don't want to risk our carry on being rejected"

No matter what advice you might read, having a bag that exceeds the clearly stated limits means risking rejection and being forced to check it for an extra fee.

Might Air France reject a bag that Delta or Lufthansa would find acceptable?

Yes, because they have established their standard, which is more restrictive than those of Delta and Lufthansa.

With Air France, you also need to be very cognizant of their weight restriction - the total of your carry-on and personal item together can only be 12 kg.

I don't want to risk our carry on being rejected, but then again I really don't want to have to buy a bag just to fit Air France specifications.

Then check the bag if it exceeds the specifications. The days of assuming that a difference of a few centimeters wont make a difference are long gone. Either use a bag that meets the most restrictive specs, if flying multiple airlines, or limit your airlines to those with larger allowances.

If you are flying on Air France, it is their rules that are pertinent.

What some other airline defines as acceptable is irrelevant.

Cabin baggage allowance
In the Economy cabin, 0 to 1 hand baggage depending on the fare chosen + 1 small bag (maximum total weight: 12 kg/26.4 lb.)
In the Premium cabin, 2 hand baggage items + 1 small bag (maximum total weight: 12 kg/26.4 lb.)
In the Business and La Première cabins, 2 hand baggage items + 1 small bag (maximum total weight: 18 kg/40 lb.)
Hand baggage dimensions
The maximum dimensions for your hand baggage are 55 x 35 x 25 cm (21.7 x 13.8 x 9.9 in.), including pockets, wheels, and handles. You must store this bag in the overhead compartment above your seat.
https://wwws.airfrance.fr/en/information/bagages/bagage-cabine-soute

How close is your bag to compliance? If you have just one bag that is just a bit over, it would take a pretty nasty gate agent to ding you, when you could have brought two bags of a slightly smaller size. ( My opinion is worth what is cost)

I did buy a bag several years ago to meet the AF dimensions and also got the lightest one I could afford (4.5#) so I would also meet the weight requirements Kim mentions.

How much does your bag weigh empty? That might be the deciding factor to me for buying a new bag.

And I agree they specify dimensions and weight and at any time can enforce them even if no-one on the forum has had that happen to them.

editing to add: It looks like you already figured this out but always go by the metric measurements. The inch measurements are rounded - some luggage companies seem to round up, some down so the metric measurement is more accurate.

I err on the side of caution. My travel companion "knew" that since Delta and AF are codeshare, AF would honor Delta. After a meltdown at the gate, his luggage was checked last minute. And lost for days. Those cms are just not worth it.

I also found out the hard way to re-check close to your travel date. I tend to book earlier than most and have had a couple of flights where the baggage restriction was decreased (of course) between booking and travel. One time a couple of days out. I was fortunate to catch it.