I use 80/12 with regular weight thread. I have used 70/10 when sewing with a fine thread on silk and 90/14 for heavier fabrics and threads and usually for quilting. I can usually use a 90/14 with Guterman when hemming jeans for my husband.
I just found this chart on Etsy. Its a pretty good guideline.
https://www.etsy.com/listing/7016777...4ff1ea0df904c2