I this we need an opposite of petite (which is also a naff word) and then stick to sizes - like the do with trouser lengths.
So
8, 10, 12,14, 16, 18, 20, 22, 24 small frame - i.e small tits
8, 10, 12,14, 16, 18, 20, 22, 24 average frame - i.e medium tits
8, 10, 12,14, 16, 18, 20, 22, 24 large frame - i.e large tits
I am a size 12 bottoms but 14/16 top due to annoying large chest and broader back and shoulders. I often have to buy 14 plus size tops to accommodate the chest and then have to take up sleeves etc - it's annoying.
If you want to really feel massive or be incentivised to go on a diet - try and buy a t shirt or a swimming costume of Amazon. Most of the stuff comes for Asia so anything larger than a 12 in considered enormous and often comes in encouraging sizes like 3XL.