Hang on, let me ask you a question. What do you think the difference is? Go on. Visualise it. Mine goes straight to colour tint, maybe frame style or perhaps “wonky” arms on one frame vs “thick” arms on the other, because that’s what we’ve been spoon fed without ever having been sat down and told explicitly. My friend Dave asked me this literally outside of school yesterday afternoon while comparing two pairs he’d innocently grabbed off his wife’s dresser by mistake, genuinely convinced there must be some intrinsic mechanical difference he hadn’t clocked yet.
There isn’t, certainly not in the way he was imagining, and that’s the interesting part to unpick rather than give a quick yes/no answer to.
The fit difference is real, but it doesn’t really care about gender
The truth is that a sunglasses sold in the “men’s” section will on average sit wider on the temples and have a longer arm length than one sold in the “ladies” section.

I’m not kidding, that is actually true, but it’s also not the marketing telling you that because well: it isn’t marketing, it’s physics. Men’s faces on average do have slightly wider dimensions and noses on average are slightly closer to the face, meaning frames will fit differently on average. But “average” is the key word in that sentence, and the word we all blink over. I’m one of those teachers with a disproportionately narrow face for a man, and I spent the best part of four years sporting frame styles that perpetually slid down my nose when I leaned over my desk because I stubbornly refused to buy sunglasses from the ladies’ rail despite the frames that consistently fit me “right” being sold there.
The secret nobody tells you is that all that stuff about men’s and ladies’ frames is almost entirely irrelevant once you know how to measure your face and glasses, because that sizing has almost nothing to do with what section of the shop you buy them from and everything to do with the lens width, bridge width and temple length of each pair, expressed as three simple numbers printed directly onto the inner arm of the frame. Three numbers that will tell you more about the proper fit of any pair in five seconds than an entire_gendered_ aisle full of sunglasses will.
I currently own a pair of sunglasses with a 52mm lens width and a generously proportioned 140mm arm that I picked out from the women’s selections because they simply fit how they’re “supposed to”, despite being obviously designed with female buyers in mind. I’ve never had one pupil suspect otherwise, let alone care enough to say something about it. My year nines would crucify me, obviously. They notice everything. Sunglasses seasons and term times, though barely overlap these days so I’ve learnt to avoid that.
It truly is baffling to watch someone wrestle reluctantly with a pair of glasses for five minutes because they’re “boy’s sunglasses” and your head is too feminine for them, only to rest back and have them cling to your face like they were custom made despite trying four others because you didn’t want to try the row labelled “girls’. Makes them lean on your nose pretty much every few minutes for the whole of your ferry journey back though, so eventually you learn.
Everything else is style and style is where this whole sexist myth lives
All of that, once you dial the pant-sizing out of the equation, is purely stylistic. Whether you wear tortoiseshell or grey tint, square frame or cat eye, aviators or wayfarers doesn’t matter if they don’t fit your face. Hell, none of that nonsense is even particularly “gendered” outside of marketing seminars. UV filtering doesn’t care about your behaviour gender identity or expression, neither does polarisation, and the screws holding your frames together aren’t cheap sexist cows just because John Lewis decided to stock that style in the men’s section.
Want to know the really depressing thing? There’s actually no hard-and-fast rule that says you can’t buy a pair of round, tortoiseshell women’s sunglasses that will actually suit the face of a man. Plenty of my guy friends do, buy them from the ladies’ rail specifically because it suits their face better, and no googly eyes were harmed in the making of those frames just because they weren’t advertised at David in the window.

Same goes for women buying oversized frames from the men’s section, which quite a few of my colleagues do because they have to in order to actually block sunlight from hitting their eyes rather than just decorating their face.
None of them were let down by their purchase performing worse because they didn’t match their genitals.
None of them found that said genitals grew an extra hinge simply by buying “the wrong gender of sunglasses”. The only people who care about this sex-based marketing when it comes to sunglasses are the people selling them.
What actually does change depending on where you look for glasses, the one useful pillar of dividing them that consistently impacts your experience in a tangible way, is lens quality and coating. That still isn’t inherently gendered in any way but you’ll find better quality lenses and coatings in certain sections based purely on what cheaper sku’s the brands decide to stock there. A pair of sunglasses with a flat, tinted lens offering no real uv protection is going to offer you almost no perceptible benefits come the actual sunny day regardless of whether the frame itself is pink, purple orPromiseMeSexyTimes navy.
I’ve worn a pair like that out on a day nearly as bright as today once. Spring sunshine reflecting off the still-present-away snow, triple-glaring at me as I struggled to finish a marking session. Came away with a migraine by lunchtime that wasn’t attributable to pupil behaviour. Look at the lens specification, and just how well the frame actually sits on your face first. Ignore the idiots selling you glasses who care more about what aisle you look in than how happy you’ll be with your purchase and you’ll do just fine.