Here's how I scale things. And frankly it's the way most guys I know scale. Some things to keep in mind:
1. You can't include most celebrities, porn stars, and anyone else who has ever appeared in a magazine on the scale. Totally skews the numbers because they are all hot. So the scale is limited to normal people.
2. Have to define the scale. Is it local or national? Since we are all from different areas of the country, have to use a national scale on this site.
3. If you haven't ever lived in another part of the country, you are probably going to scale on a local level whether you intend to or not. So keep that in mind. Somebody from California is going to have higher standards than someone from Pennsylvania. Vacation doesn't count.
So here's my scale (I've lived in the Midwest, Northeast and Greece/Italy for extended time periods)
9.5-10: No doubters. No physical flaws. Perfect body and a face that's at least in the upper 10% of women. Only about 1-3% of women fit this bill.
8-9.5: Very hot girls. Face is in the top 25%. Body is very good and likely not overweight at all. May have minor issues such as smaller breasts (although some men like that), a small mole, or are shorter/taller than the median. About 15-20% of women should fall in this range. These are girls you would absolutely have no hesitation dating and showing off to your friends.
6-7.5: Average to Above Average: Nothing spectacular about the girl, but nothing bothersome either. May lack in one area but excel in another. This also covers girls with very nice faces but less than stellar bodies. About 30-35% of girls fall in this range. You wouldn't brag about this girl's looks if she was your girlfriend but you wouldn't get ragged on either. Most guys will marry a girl like this as having a wife in the higher ranges creates other problems.
4.5-5.5: Girls with average bodies but a below average face. Or girls that are moderately overweight but are naturally pretty. About 30-35% of women fall in this range. Wouldn't hook up with this girl unless drunk and she grabs your junk or if she becomes a Mermaid.
<4.5: Reserved for girls with clear weight problems and girls you wouldn't hook up with under any circumstance. Bad teeth, excessively hairy arms, etc. All these girls get lumped into this category and it's not really worth defining further. 10-15% of women here.