There is some trial and error involved. You can use the size charts provided by many brands. Measure your waist and use that as the "hip" measurement. Ignore the number given on the chart for waist.
Definitely look for a wider gusset. You'll be more comfortable.
Lastly, you'll have to try different styles to find which is most comfy for you. I'm fortunate that I find all styles comfy, so I just pick the prettiest colors and prints I can find.
If you can find the courage and go to a Department store when it is quiet the SA will make a good guess or maybe even measure you. The SA in my case looked at me and said I was a size 7. I bought a pair and tried them on when I got home and yes 7 worked just fine.
Size 7 is also a L
I agree with Kelli, use the hip measurement to match your waist.
Also, give consideration to how big you member is and whether you want room "to grow".
A size 7 is good up to a 40" waist and if you prefer briefs, allows that room for the most part.
I am a 42" waist and I am larger than most men, so I prefer a size 8 or 9 nylon brief. (VF Ravissant).
The "granny panty" design allows for a great feeling and has all the room I need.
Bikini panties just don't do it for me. Everything is always too tight, with the exception of when I wear my bike shorts.
The extra support and extra smooth feel that a bikini panty gives helps in keeping everything "up front" so it helps in decreasing the numbness a guy gets from a road bike seat.
For Kerry's point 1: I would be between their opinion and kelli's/Dane's. I am usually a size 5/small. I subtract one inch from my waist and add one inch to my hip and compare to the sizing chart the company has. But yes, point 3 really affects things. Years ago I bought a handful of Warners pieces and found that I would have to buy their size 4, which is really small for other companies. Also, even within one brand the sizing can vary quite a bit sometimes. I tried a handful of Victoria Secret styles years ago and found one size 6 that was too tight (it was a laser cut edge style) and one size 5 thong was kind of loose around the waist (a more stretchy microfiber/nylon material).
For point 2: I usually go for stretchy material AND wide gussets to cover. And yes, seeing the panties yourself in the store is a ton better than shopping online. From my years of shopping for (mostly bikini style) panties online, it is just too difficult to judge how wide the gusset is and how stretchy the material is based on pictures of a woman wearing them. It's also hard to judge the waist band size. Sadly, I live somewhere it would be too high of a chance of "getting caught" in the store by someone I know because I would be embarrassed by it. But if you have the money to afford buying stuff that may not fit, then you can always shop online and donate any new & unused pairs to an organization like "The Undies Project."
I would add: I have also heard others say this same thing in the past: Don't try to push everything back between your legs. That usually makes things worse.
Really good question. Recently I had a really useful conversation about getting my size right with a delightful lady who makes and sells nylon and satin knickers/panties with men in mind. Her advice to me worked really well. She asked me to measure a pair of knickers that I already have and know fit me perfectly and then run it past a size chart she sent me via email. That was great advice because that was a perfect way of knowing anything I bought from her would be a perfect fit.
Before I knew of her I had suffered disappointment more than once by buying cheap knickers off eBay that were shipped over from China and although the items were clearly marked as my size but were way too small for me to wear.
I found mediums in most sizes work best for me though I've gone small or large depending on the kind of panty. Thongs I often get bigger because they often have less in the front and while I am not particularly endowed it still helps with that.
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Wearing pretty panties since 10/2014.
No men's underwear in my possession since 12/30/2023.