How long does it take for sperm to build back up after ejaculating?

You produce sperm every day, but a full sperm regeneration cycle (spermatogenesis) takes about 64 days. Spermatogenesis is the complete cycle of sperm production and maturation. During sperm production, also known as spermatogenesis, each testicle will produce about a few million sperm per day, meaning that every second that passes, 1500 sperm are born.