How Much Yarn Per Row?

A simple rule of thumb to estimate how much yarn you need per row:
Spread out your work to get the full width of the piece. With your remaining yarn, loosely extend it across the work 3 times. If you have enough yarn to do that, you have enough to knit the row. The only exception is if you have yarn gobbling features like bobbles or cables. If you are binding off, you'll need at least four lengths as this procedure takes that much more to do it properly.