The conception process requires only one sperm to fertilize an egg to result in pregnancy. The chances of pregnancy are not solely dependent on the number of sperm but also on the quality of the sperm and a multitude of other factors, including the female's reproductive health. Knowing that sperm count is important, having a high semen volume also means more sperm per ejaculation.
A sperm concentration of at least 15 million sperm per milliliter (ml) of semen is considered within the normal range. There should be a total of at least 39 million sperm in the entire ejaculate. You can conceive with a lower sperm count, but this is the average range, and is considered to be a "healthy" starting point for measuring sperm count.
A typical ejaculate contains tens to hundreds of millions of sperm. Despite this seemingly massive number:
While technically it takes just one sperm to fertilize an egg, the presence of a large number of healthy sperm in the ejaculate increases the likelihood that one of them will successfully reach and fertilize the egg. Semen volume, and the volume of sperm within said semen are both extremely important. An egg can even be fertilized from the sperm found within precum. Yes, you can get pregnant from precum!
A "normal" sperm count, as defined by the World Health Organization (WHO) in their 2010 guidelines, is characterized as:
Sperm count is just one of many aspects of male fertility. Other important parameters include:
While only one sperm is required to fertilize an egg, the chances of successful fertilization increase with a higher sperm count. A normal sperm concentration is at least 15 million sperm per milliliter of semen and a total sperm count of at least 39 million per ejaculate. The motility, morphology, and other attributes of the sperm play crucial roles in fertility as well. Even if a man's sperm count is within the "normal" range, it doesn't ensure fertility, just as a count below this range doesn't automatically indicate infertility. Fertility is multifaceted, and when concerns arise, you may need to look into lifestyle changes, semen volume supplements, sperm health supplements, and talking to a fertility specialist.
WHO 2010 male reproductive health study: https://www.who.int/docs/default-source/reproductive-health/srhr-documents/infertility/examination-and-processing-of-human-semen-5ed-eng.pdf