Am I fertile on the21st if I've got mymenstruation from dec.9 to 15

Hi sheilamarie,

A rough guide is that you would ovulate about 12-16 days before the next period is due. However, this is only a guide as many women will ovulate a bit sooner or a bit later than that regardless of the length of their cycle (with the length of a cycle being from day one of a period to the day before the next period starts, not how long a period lasts).

If you are trying to become pregnant, you may want to consider having sex every other day throughout a cycle, or every third day with a couple of extra sessions in the days prior to possible ovulation, to give you the best odds. Even then, it can take quite some time as there is more to pregnancy than just timing, although that is obviously an important factor.

There are plenty of ovulation calendars online. They are estimates and also depend on days of cycle. But they are not always right, some women ovulate early or late. The only way you willl know ovulation timing is by testing for it or following with body temp changes.