An interesting question, but the correct answer depends on several factors: the last time you ejaculated, age, how many sperm your own body produces, testosterone-levels, and some studies even suggest that the attractiveness (this is not only about whether you find her physically attractive, but there are psychological factors at play too; e.g., if she is a virgin, and is healthy) of the person you have sex with will increase sperm production (see: Kelly & Jennions, 2011). General estimates as to the average number of sperm per ejaculation range from 20 million (considered very low) to about 1.2 billion or so.
Each milliliter of semen contains 20-300 million sperm cells and each ejaculation is about 2 to 5 milliliters. So anywhere from 40 million sperm cells to 1500 million sperm cells. It varies man to man and of course whether it is the first ejaculation or not.
they say around 3 to 6 teaspoons depending on age and other factores