From people's previous review they said to go a size down to get that perfect fit. I only did it after seeing someone mention the same size I am - I'm a 10-12 in AU size so that means Medium for most wear. So k went to a small. I got it today, and sized it by eye against me, the length reaches mid-calf and the material is super firm - like shapewear spandex wear which means it's gonna stretch to accommodate. I'm assuming we're all not skinny 😅 and are in the stage of wanting to lose that tummy chub and I know when I move in shapewear, the material rolls down on my rolls 🤣 - so my take is that it's gonna kill your waistline but it's gonna be pinching it real tight on your stomach if you usually stretch it up a bit, I do that because it just leaves line marks under my belly line. The material, as I feel right now, is super duper firm and tight, and that could be just the gradual thing that loosens overtime, but I would be ok with it since it's my goal to lose weight. Also to clarify I bought the short biker shorts with pockets, it has pockets on both sides and it covers nearly my entire top calf - but that's also because I don't have much legs for days (short-stack woman).
Either way it's good material, it's firm, it's definitely gonna be a pincher on the tummy, definitely has that manufactured new smell to it, seems it's gonna handle sweat and also gives you much mobility for both your phone and your movements.
Does that mean I'm unhappy with the Small? Nope, I'm happy with the buy because it does fit perfectly so it's all good. Also my goal is to lose weight, if I bought it at M to accommodate my current weight I won't be able to tell if I'm losing weight or not, I don't have a scale and the Google fit app is weird to me, so I'm using that as a reference.
Edit: I tried it on yesterday and the band on the waistline is super firm against my tummy, that it stood to support it well. Even as I ran on my treadmill it was great, great mobility and doesn't feel suffocating. The comfort is there too and I'm a happy chap honestly.