How much does the volume of sperm / semen in each orgasm vary, in one person, from time to time?

Varies. Amount of semen ejected during ejaculation will vary widely between men and may contain between 0.1-10 milliliters ( note that a teaspoon is 5 ml and a tablespoo is 15 ml). Adult semen volume is affected by the time that has passed since the previous ejaculation; larger semen volumes are seen with greater durations of abstinence. The duration of stimulation leading to ejaculation also affects vol.