To determine the width of the front pieces, start with the width of the back, subtract the width of the button bands (usually 1") and divide the remaining width by 2. This gives you the width of each front piece. Or said another way, the front piece is half the width of the back less half the width of the button or buttonhole band. This figure might have to be adjusted when the pattern stitch is considered.
When planning the number of ribs to include in the button/hole bands, just hold up the back ribbing and count. Keep in mind that 2 rows of double crochet take 5 single crochet in the side.
Most patterns place the bottom buttonhole 3/4" from the bottom, the top buttonhole 3/4" from the top, and space the remaining 3 or 4 buttons equally. In this example, 3/4" is 4 rows or 2 ribs.
Total rows in band- 56
Top and bottom hole will be in the 4th row from the end so subtract 8 from 56=48
Total rows to use to evenly space 5 holes will be 48. So divide 48 by 4=12.[since the 4th row is a buttonhole, and the last 4 rows are after the holes, you really have 4 holes to evenly space over 48 rows.]
5 BUTTONHOLES IN 56 ROWS
Buttonhole #1 will be in the 4th row.
Buttonholes #2-5 will be in the 12th row following each buttonhole. Then 4 rows after the last hole for a total of 56.
If 6 buttonholes are needed, stay with 56 rows of ribbing.
Subtract 8 rows from 56 rows and divide 48 by 5=9.6. Simply adjust the rows between holes so that all are even. There will be 8 rows between the top hole and the next one down; 10 rows between the other holes.
This method will work whether the bands are ribbed or plain, crochet or knit, made separately and sewn in place later or made right on the front edges.
RIBBED CASING FOR HOOD:
First, the drawstring. For a baby jacket take a piece of yarn 190" long, double it, and twist it to the right until it starts to curl up on itself. Then double it and let it curl on itself. Work the twist with your fingers so it is smooth. Tie a knot 5" from each end. The extra 5" can be used to tie on a pompom or tassel. (Twisting the yarn by hand takes a very long time. Put one end of the yarn in a hand or power drill chuck and twist it that way. I use the lid of the lettuce spinner. My wife thinks it is hilarious but it gets the drawstring twisted.)
Make the ribbing for the casing in the normal manner- with fingering yarn chain 10 and work sc into 9 chains works very well. When the casing is long enough, change to the larger hook, chain 1, and turn your work sideways. [Most patterns indicate you should just work the hood fabric in the same manner as the other pieces, or even make the casing separately and sew it on later.] Add the drawstring and fold the casing in half-why struggle pulling the drawstring through later? Carefully align the ribs of the casing and sc through both layers of work. The resulting casing is smoothly joined to the hood fabric and takes only slightly more time than doing the foundation row through one layer of ribbing. This first row -the foundation row- could either be simply sc across- if the hood consists of an open stitch pattern, or could be an increase row (i.e. sc in each of the next 3 row ends, 2 sc in the next row end. Repeat across.[For every 4 rows in the ribbing you now have 5 sc for the body of the hood]). A decrease row could be worked in a similar manner. [sc in each of the next 3 sc, then sc2tog. For every 5 sc in the first row, there are 4 sc in the decrease row.]
To evenly space any number of increases or decreases in a row, refer back to the section on spacing buttonholes. The math technique will be the same.