It's been a minute since I've flown United Airlines. Are they strict when it comes to actual size of carry-on suitcases? My carry-on dimensions are 1/2 to 1 inches greater than the allowable dimensions listed on their website. (I strongly prefer carry-ons and always try to avoid checking in luggage)

I have never had them check. Not saying they couldn't, but I've never had an issue.

Is it hard or soft side?
Soft side you can cram it down if need be.

Hard side.....depends on the gate agent.

I like the MONOS carry-on for hard side

I use a soft sided carry-on. Thanks!

Which side is larger than the requirements? Some planes have more room than others.

Ive never seen them check a bag that wasn't obviously too large. Your average "carry on" will likely be close enough. I've got several and never measured any of them.

Your biggest problem will be if somehow it doesn't fit in the overhead. But then the worst that'll happen is having to gate check it. But I've seen some large bags crammed in.

The allowable length is 22 inches, but mine is actually 23 inches. My width and depth are roughly 1/2 inch larger.

Depends on the gate agent. I traveled for work with the same carryon every week and did have an agent or two make me prove its size.

Plane/your boarding zone will matter too.

Regional jet and later boarding, probably gate checked. Consulting/business flight, high probability gate check too.

Boarding group and aircraft are important info needed

Just flew United to Maui last week ... 2 planes ... Airbus 320 and Boeing 777.

Our carry-on is a 15.5 x 9 x 22.5 hard-sided roller ... no issues stowing it overhead on the 320 ... but on the 777 they were really hounding passengers about gate-checking roller bags. Turns out once we boarded I understood why - roller bags that were within the size requirements actually didn't fit properly in the overhead bins over the middle seating section.

You know they always tell you to put your bags in rollers first? If you did that in the overheads on the outside rows, it was fine - but in the middle overheads the bags were mostly too long, and had to go in sideways, which the flight attendants then ***** at you about.

So they was a lot of moving smaller bags and backpacks from the sides to the middle overheads to make room for the larger bags on the sides.

I didn't see anyone's carry-on get denied due to size, but they were really pushing the gate-check. For what it's worth, we did gate-check our roller on the 777 both times - it was free and we had no issues.

We fly United often. Usually in Group 2 so we rarely have an issue. The newer or remodeled interiors have added space in the overhead and that has helped. I would just go for it and gate check it if they insist.