How long to let baby cry?

How long have you let your babies cry before soothing them? My daughter can definitely self soothe because she has done it before but she really cries for a while at bedtime. We are trying with not much luck to get her to sleep in her crib. It breaks my heart hearing her cry but realize she may have to as she learns to soothe herself. We've maybe let her cry 5 minutes. I just dont want to let her cry too long, but an age appropriate time frame. I feel like now is the time she needs to learn to sleep in her crib and self soothe. She can definitely go longer periods of crying than she used to before she tires herself out. Some friends and family have told me they waited too long with their babies and it was horrible.