how many yards of yarn do i need to crochet a baby Afghan?

Sorry. Can't answer that. Only you can. You need to find out your gauge. When you figure out how many stitches per inch you are able to do and make it look like you want it, and figure out how big you want it to be, then you can figure out how much yarn you will need.

There are just too many variables to be able to answer your question. Everyone works differently, and depending on what stitch you are using, what size of hook, size of yarn, pattern, etc. it can really vary.

You need to measure a small piece of work in the pattern you want to use. (You get to practice your stitch this way too) Measure the square inches you get. Measure accurately! Then rip it out, and measure how much yarn you used, or weigh your sample.

When you determine the size of the blanket you want (how big is a baby afghan?), you will know how many square inches you need, and knowing the size of your sample, you will be able to calculate the yardage you need. Give this as a problem to your grade school kids, and let them see how they can use math in everyday life. Then see how accurate they are when you finally make the afghan and see how much yarn you used. Give a prize to the closest answer!