As a general rule of thumb you need four times the wool to cover an area. Calculators are included inside The Rug Hooking Journey* membership inside The Basics course.
*The Rug Hooking Journey is a paid membership site offering hundreds of hours of videos created since 2016.
In this video I will teach you how to create your factor or how many layers do you need for your rug hooking. While the average is four times, you might need significantly more. The only way to know for sure it to test.