Semen volume is defined as the amount of semen, the fluid that contains sperm, produced during one ejaculation. According to the World Health Organization (WHO), semen volume can range anywhere between 0.8 milliliters to 7.6 milliliters. The average is 1–5 milliliters. Semen volume affects sperm concentration, and volume that's abnormally low may affect fertility.

What is semen volume?

Semen volume is the amount of semen ejaculated from the penis. A normal semen volume ranges from 1.5 to 5 milliliters, or between ¼ and 1 teaspoon, per ejaculation. The fluids that make up the semen volume come from several sexual glands and organs, namely the seminal vesicles, prostate, testicles, epididymis, and bulbourethral glands.

Semen volume and male fertility

Sufficient semen volume is necessary to carry sperm and enable it to fertilize an egg. As a result, semen volume is one of the factors examined in a semen analysis to evaluate fertility.

Decreased semen volume may indicate a number of medical condition, including: 

• Retrograde ejaculation, in which the semen flows back into the bladder instead of out of the urethra.
• Anejaculation or “dry orgasm,” where no semen is ejaculated at all. Potential causes include retrograde ejaculation, spinal cord damage, or nerve damage.
• Hypogonadism, which results in low testosterone levels that can cause reduced secretions from sexual organs.
• Ejaculatory duct obstruction, meaning something that’s blocking the tubes that transport semen in the testes.
• Missing the seminal vesicles, a congenital condition. 

Testing semen volume

Semen is typically collected through masturbation into a sterile container. It’s recommended that you practice abstinence for 2 to 5 days before collecting a semen sample.

After collection, the semen volume may be determined either by weighing the sample and calculating the volume using a known density, or transferring the sample to a graduated cylinder to measure the volume.

Semen volume is used to calculate the sperm concentration and total sperm count. The sperm concentration refers to the number of sperm present per milliliter of semen. By multiplying this by the total semen volume, you can determine the total sperm count in a semen sample.

While semen volume is not a highly influential factor on its own, it may go hand-in-hand with low total sperm count, or may indicate a larger issue affecting fertility.