Trading down rares to commons - how many exactly?

[TheCarmenStar]

So I have a few old rares and have been looking to trade them down for commons/uncommons on my wl, and while I know theres all those elaborate trading guides with lots of math, I haven't been able to find a simple "a rare from this year would probably be worth this many commons from 2024!"

I know the whole thing about 2 of one rarity being worth 1 of the next rarity up from the same year, but when I'm trying to trade bulk, it just feels like a lot of math for every individual pet across years that I'm wanting from someone else. but maybe I just get overwhelmed by a lot of numbers easily

So for example, this guy from 2010



My Horror's extension tells me he's worth 0.1 MA, so how many uncommons and below would that be in pets from, say, 2020? 2021? and so on? Is there any faster way to calculate these things than just adding and converting a whole bunch of 2's? every time I think I've got it and actually go to add stuff to my trade, it just suddenly feels like I'm asking for a lot, but maybe that's the norm here and I'm just not used to it yet?

or should I just be paying attention to C$ worth rather than calculating these dates and amounts?

any help appreciated!