I want to make my dd a simple little a-line dress and not exactly
sure how to do it. I was thinking that what I would need to do is
figure out how many stitches I need at the chest measurement and
how many I need at the widest part of the bottom and get the
difference then calculate how many rows it will take to get the length
I want and then I should be able to calculate how often to do the
increase rows to get the right width and length. Are increases in
an A-line evenly spaced over the whole length?
TIA,
Libbie 
I went looking for a pattern that might serve as a guide for you. I found this pattern. This is for sizes 1-6 and the gauge may be different from the yarn you’d like to use, but I thought it might help you with the decreases as you go up. This one flares more than you might want. Here is another one. I actually like this one and it is A-line and sized 2-12. I think I’ll book mark that one myself. 
The thinking you had going sounded like it would work and with these to look at maybe you’ll be able to figure it out even easier. Good luck.
The Berroco pattern is exactly what I was looking for, thank you!
I want to do a bit of cabling on it and knit in th eround rather than
in two pieces but the basic design is perfect!
Libbie 