Size matters, at least for charity quilts.
Here are some common sizes that you can use as an approximate guideline:
Ronald McDonald House - 40-45" wide by 48-60" long (kid prints)
Randall Children's Hospital - 36-40" wide by 40-45" long (baby prints)
Mt. Hood Legacy Hospital Passage - 40" x 60" (adult)
Our Just Future Women's Shelter - approximately 50" x 70" (any prints)
Hopewell Hospice - lap size to throw size (any prints)