1) Quantity sold

2) Gross Trade Sales (Quantity * Base Selling Price)

3) Net Trade Sales (GTS * (1- sum of discounts))

4) Gross Profit (NTS - COGS)

All of this data is aggregated on SKU level. What I would like to do is taking into account Quantity & NTS & Gross Profit values calculate a rating for each SKU showing it's efficiency. I'm not that good at maths, so some of my questions might seem pretty simple for you, but still:

1) Do I really need to include Qty into my model since it's already included in NTS?

2) I've been using following formula to calculate a rating for each SKU and further distribute it among preset thresholds for each rating starting from 1 to 5:

(100 - sqrt( ((100 - NTS% in GTS)^2 + (100 - GP% in NTS)^2)/2 )*100

Is it a possible/accurate way to distribute all SKU's based on how efficiently they're sold and how profitable they are? Are there any other models/formulas you can advise to reach my goal? Thanks in advance!