Guides
Plain-language answers with the sources named on each page. Find the question closest to yours; each guide pairs with the tool that continues it.
Dates and counting
Working out dates from your own records.
How to calculate your next period date
How do I work out my next period from my own dates?
How to know when your period is ending (or over)
Is my period over — and which day counts as the last?
Late, or about to start
What a delay or early signs mean, and what to do first.
Why is my period late? 10 common causes
Why is my period late, and what should I do first?
Signs your period is coming tomorrow: the 9 to watch for
Which signs show a period is on its way?
After a pregnancy or a loss
When cycles come back, and the lines for seeing a doctor.
First period after a miscarriage: when it returns and what to expect
When will my period come back after a miscarriage?
First period after birth: when it returns and what is normal
When does my period come back after having a baby?
Counting a pregnancy
Why the weeks are counted the way they are.
Why is pregnancy counted from your last period?
Why am I already “4 weeks pregnant” about two weeks after conception?
This tool provides estimates for personal planning only and is not a substitute for professional medical advice, diagnosis or treatment. Predictions must not be used as contraception. If you have concerns about your cycle, heavy bleeding, severe pain or missed periods, please consult a licensed clinician.