Recommended Notion: Kitchen Scale by Nicewell
A kitchen scale is a great tool for weighing your yarn if you need to split your yarn ball into two for two-at-a-time knitting.
To divide your yarn in half, first wind your yarn into a ball from the hank.
Then, weigh the yarn ball on the kitchen scale and make a note of the total weight in grams and calculate what would be half that weight. Then, leaving the yarn on the kitchen scale, begin to wind, stopping when the yarn weighs half what it used to. Cut your yarn and wind the remaining half into a ball.