Question: how long does it take sperm to build back up after ejaculation?
Answer: Your testicles are constantly producing new sperm in spermatogenesis. The full process takes about 64 days. During spermatogenesis, your testicles make several million sperm per day — about 1,500 per second. By the end of a full sperm production cycle, you can regenerate up to 8 billion sperm.