there are a few things that determine the health of a sperm. the first is sperm count. about 15 million or more for every milliliter (ml) of semen is considered normal. the more you have the more likely one of those sperm will fertilize an egg. the second metric we look at is movement. about 40% of your sperm need to be strong swimmers in order to be considered fertile. the 3rd metric is shape. a healthy sperm has a rounded head and a long, strong tail.