took me about 15-20 pounds but i jumped from 14 to 10 and now 8

From my perspective, the question is hard to answer. I went from 208 to 161 lbs and from jeans size 16 to size 4 (current). I don't know how many pounds I lost in between individual jeans sizes, whenever my jeans became too baggy I either pulled out a smaller size from my closet or bought a new pair.

Pretty much each pair of jeans that I wore along this journey was of a different brand and I think there is a lot inconsistencies between sizes of different brands (e.g. you can easily be a size 6 in brand A but a size 8 if not 10 in size B) so it's hard to say.

Also, because each of us can be shaped somewhat differently, the number of pounds required to move one size to a smaller one may vary from one person to another. You may lose a lot of weight in your boobs, for example, but not so much in the hip/butt area. I, on the contrary, will always have boobs and the weights disappears from elsewhere.
I believe another poster mentioned she was in size 10 weighing 170. I am in size 4 weighing 161. I mention this just to illustrate what I said above.

this is so true. when I was 190 I was an 18.

I lost 33 pounds and went from a size 14 to size 8, but jeans are weird. It's a piece of clothing that you always have to try on and I have discovered that size doesn't matter. It's all in the way they fit.

Oh yeah, this varies a lot. I'm at 167 and I'm very short and I'm just recently able to wear 16s. Some large pants (like sweats) are starting to drown on me, so in those I'm probably now a medium. Huge variation on anything size-wise I think.