The size of the ovum

The ovum or egg cell is the largest cell in the human body and under the right circumstances it is visible to the naked eye without the aid of a microscope.

Females are born with all the premature egg cells (oocytes) they will ever have and no new ones will be made during their lifetime. 

A female is born with approximately 1,000,000 oocytes. Many oocytes will die before the female reaches puberty, in a rate of about 10,000 per month, and thus the total number which will remain is nearly 300,000. 

The number of eggs that die after the start of the menstrual cycle, is reduced by 1,000 per month, or about 30 per day. 

During the ovulation, only a single oocyte will mature and become an ovum.

When the female runs out of eggs, most often around their 50s, the ovaries cease to make oestrogen, and so the menopause begins. 

The human ovum measures approximately 0.13 mm (0.0051 in) in diameter, or about 1/4 the size of a grain of salt. 

The human ovum is also about 25 times larger than the head of the human sperm.

This interactive from the University of Utah's Learn Genetics webpage gives you the opportunity to see how various small things compare to one another.