It started off with being based on the UK sales numbers for each position in the top 40 (divided by 1000 obviously). But as 2013 rolled around, it strayed from that a bit. It's why my points are really low in Q1 of 2013.
#40: around 8-9 points.
#30: around 12-15 points.
#20: around 19-22 points.
#17 (in the top 17 era): 20-25 points
#15: around 25-30 points, up to 35 in competitive weeks.
#10: generally: minimum 30 points; maximum 50 points; depending on the week. I try to keep this at an average of 40 points as much as possible.
#5: usually around 55-80 points; 65 points tends to be the average.
#3: usually around 65-90 points; 75 points tends to be the average.
The #1 (or any big song in the top 5-ish)
anything below 75 points: weak #1. Usually #1 that only gets there because something has to be #1. Generally songs that wouldn't usually go #1 in a more competitive week, or songs that have already peaked. 2013 had a lot of the former.
75-89 points: average
90-109 points: above average
110-149 points: #SMASH!!!
150-199 points: obsession territory
200-249 points: "OMG THIS IS THE BEST SONG EVER MADE IN THE HISTORY OF MUSIC!!!"
250-299 points: life defining
300+ points: well now we're just talking crazy
1000+: My million-sellers. Pretty much reserved for life defining singles.
Examples: Bad Romance, Feel The Love, Your Love Is My Drug, Hideaway, We Found Love, Prayer In C
800-999: Huge to major smash hit. They aren't life defining, though.
Examples: Party Rock Anthem, Like A G6, Rude Boy, Moves Like Jagger, Fire Burning, I Got U
600-799: Big to very big smash hit. 600 tends to be the barrier for what I'd consider a big hit on my chart.
Examples: Super Bass, Primadonna, In My Mind, Talk Dirty, I Love It, White Noise
400-599: Average-sized to still pretty significant-sized hits. Also tends to be a section of "why was that a #1?"
Examples: Run This Town, So Good, According To You, Pumped Up Kicks, Higher (Free), 5 AM
300-399: Tends to be the barrier of being a hit on my chart. Also quite a bit of 2013+ songs wind up here.
Examples: I Do Not Hook Up, Domino, Boomerang, Hey Baby (Drop It To The Floor), Love Like Woe, My First Kiss
100-299: A sea of underrated gems and "I charted that?"'s. Also a good chunk of non top 10 hits in the top 40 era.
Examples: Winner, Paradise, Born To Die, Loving You Is Easy, Global Concepts, Eenie Meenie
below 100: irrelevant
Examples: Digital Girl, Good Kisser, Ooh La La, Here's To Never Growing Up, Finally Found You, Dirt Road Anthem