How do you figure your DPO?

Question

July 8th so am I 18 DPO?

Answer 1

You either ASSUME 14 days after the start of your last menstrual period, or you track BBT and watch  for the temperature spike that indicates ovulation.

Answer 2

As of today you would be 17 dpo, you count from the day after you ovulate. :)

Answer 3

You need to know when you ovulated. You can go by what they say is "average" (a 28 day cycle with ovulation occurring on day 14) or you can be more accurate and learn about charting your Basal Body Temperature or use an OPK (ovulation prediction kit).