How do you calculate you're next period?

Answer 1

The typical menstrual cycle is 28 days, but yours may differ - count from day one of your period up until your next period, this is one cycle, then figure out your average cycle from your last six cycles.

Your average cycle length will change over time so it's a good idea to use a period tracking app to keep track for you or use Fertility Awareness Method to keep track of exactly where you are in your cycle daily. Remember that anything up to a weeks variation in your cycle is normal, also that occasionally cycles will change or things such as stress and ill health may delay your cycle.