Cale is advancing through diaper sizes more quickly than Karston did, that's for sure! Just this week I traded in a case of diapers for the next larger size because he's not using nearly as many of the smaller sizes as Karston did. Cale's gaining weight at a normal rate, but that's a slightly faster rate than Karston followed, plus Cale started out weighing more.
We started with Huggies size N because we like the umbilical cut-out, and used 80. That's when he kicked out his cord stump (and cried about it). Size N was just getting too small by then, both by fit and by the "up to 10 pounds" rating.
Next we went through 88 Pampers Swaddlers size 1 (8 to 14 pounds). Just as I remember, 12 pounds was a good time to go to the next size. We've had better luck on the low side of the weight ratings. As a side note, the Pampers size 1 seems a little larger than the Huggies size 1.
Cale's not even 13 pounds now, but we started a case of Pampers Swaddlers size 1-2 rated for up to 15 pounds. When we got to the bottom of that case, that size was getting too small for a comfortable fit. We used many more size 1-2 on Karston!
So now we're using a mini-case of 96 size 2 (12 to 18 pounds) diapers, and I expect we'll want the elbow room of moving on to Pampers Swaddlers size 2-3 by the time it's empty. They didn't make size 2-3 when Karston would have worn them, and I remember the jump from size 2 to size 3 was larger than I would have liked. So I wouldn't be surprised if we only buy size 2 once, like all of the preceding sizes except N. Remarkably enough, Karston was wearing size 3 not that long ago ...