I rate them based on my personal opinion. I base my personal opinion on a full day of wear of a given fragrance in a controlled environment (and, ideally, with a 3rd party observer present to help me judge sillage more objectively).
I utilize the entire star rating system available on Parfumo:
• 1 to 2.5 stars is for horrible experiences.
Those are perfumes I scrub off (or only manage to resist scrubbing off through sheer willpower) or get an otherwise viscerally negative reaction to. within this group I reserve the 1 star rating for perfumes that either smell like they are actively trying to kill me or completely fall apart as a product.
For example,
Hero Parfum Intense smelled like someone pepper sprayed me, put me inside of a stack of car tires and then lit them on fire. Worst headache a perfume ever gave me.
On the other hand,
501 - Iris & Vanilla was tolerable scent-wise, but it never set. For the first 4 hours I was able to scoop off the oily film from my skin with my fingers. It transferred to clothing if I accidentally brushed against it, and to other people.
In two very different ways, but I judged that both of these were a hazard and rated them as such.
• 3 to 4 stars is for perfumes that are bad, but at least they're not trying to murder me.
If I get a headache from them – I can fix it with a few over the counter painkillers. It's anything too synthetic, too cloying, too skewed in a singular direction (and yet failing even at that) or on the contrary – feels like it's stumbling over the place without a clear vision... Citruses that smell like cleaning supplies. Flowers that smell like cat piss. Musk that smells like chalk. Any fragrance that doesn't bother saying anything past "look at me, I'm such a sweet feminine woman" or "I'm a manly man"! Anything else that for some reason I despise on a personal level...
Gods, if I didn't need sleep and sustenance, I could go on forever. My reasons to complain about smells I dislike are endless, lol.
• 4.5 to 5.5 starsis the forgettable pile.
They're not that horrible. They may have some redeeming qualities. Or interesting concepts. Or maybe they're even okay. Maybe even a little bit nice, actually! But at the end of the day once time comes to review the results, my opinion boils down to a variation of "well, that definitely was a perfume".
• 6 to 6.5starsis for interesting and generally likeable things that still fall short of my expectations for some reason.
I appreciate them for what they are. I often enjoy them while they last. They do their thing relatively well, whatever that thing is. I'm impressed by their vision, or by the well-rounded composition, or by the concept, or by any other part of them. They're fine. I am also generally not interested in ever touching them again.
• 7 to 8 stars is for stuff that I personally find neat!
They do something I find really cool! They're unique, they're well made, they're very tasty. They make me feel good while they last, and at the very least make me consider wearing them again. Even things I end up deciding against buying/keeping, I can easily recommend to other people who might be more interested in that sort of thing. If they promise a specific concept – they deliver on it. If they surprise me – it's a lovable surprise.
It's the smells that make my day better by being a part of it.
• 8.5 to 9.5 stars is for the Loewe pile scents I personally love and must have.
Perfumes I've tried and went "woah, you understand me so well". Perfumes I would kiss on the lips and with tongue. Perfumes that I've tried and just went "yeah, I gotta have this one".
• 10 stars is for favorites.
We're long past any semblance of objectivity here. Who cares how good these are, THEY ARE MINE. MY PRECIOUSSSsss ٩(ˊᗜˋ*)و ♡
TL;DR: looking back at the whole thing and keeping it simple, I consider 6 stars a kind of cutoff point. Above 6 – it's generally nice perfumes that are ranked higher or lower based on my personal taste. Below – is my personal hell that I engage with because I'm addicted to having opinions, lol.
When it comes to sillage, longevity, bottle design, well...
Longevity is easy. It's hours. 1 to 9 stars are for 1 to 9 hours it stays on my skin. If a perfume lasts 10 hours or longer – I note it in the review and give it a 10.
Bottle design is also easy. 5 is the "its certainly a bottle that holds perfume" middle ground. Anything more – I liked it more than the average. Anything less – I liked it less.
Sillage is more difficult. It's hard to judge it alone, and it's hard to judge it objectively. To me, anything less than a 4 is for perfumes that stay close to the skin. Depends on how close they stay, how weak the scent is overall, if I can feel the trail if I move my arms or if I have to smell them directly. 4 to 5 – the perfume cloud is present and can be felt in my immediate vicinity, but once you leave my personal space – you're safe. Your coworkers at the office shouldn't hate you. You aren't likely to give anyone a headache outside of very tightly crowded spaces. 6 and above are for perfumes that can be felt an arm's length away from the wearer (and more!). The higher the number, the larger the cloud. But it's hard to judge from the number alone if the cloud fills the whole room. Does it leave a thick lasting trail? Does it enter the bar before you do and suffocate half of the regulars and at least three employees? So I tend to just specify those details in my reviews.
I'm lucky to have a partner who's willing to smell me and give his unbiased opinion on how large my presence is, so I can be a bit more objective with this particular stat. If he's in the mood, sometimes I also get to spray it on him once the air is clear and cross test the fragrance to see how it behaves on a different body.
I am also unable to shut up once I start talking about an interesting topic. Gods, this post is already too huge, I wonder if it'll send, lol.