How do you make a yarn crop top?

How many yarns does it take to make a top?

Estimating How Much Yarn to Buy

Yarn Weight Category Stitches per Inch Yards Needed for an Adult Sweater
3 Light 5 to 6 1,000 to 2,000
4 Medium 4 to 5 800 to 1,500
5 Bulky 3 to 4 600 to 1,200
6 Super bulky 1.5 to 3 400 to 800
THIS IS FUN:  Why use surgical staples instead of stitches?