The fertile days vary each cycle, even when your periods are regular, but calendar methods work on the basis that everyone is the same so are very often not accurate for an individual woman.  Tracking your personal fertility hormones is a sure way to know when your fertile days are, and it’s proven in a study to be twice as accurate as traditional calendar methods4.
The Clearblue Fertility Monitor accurately tracks your 2 key fertility hormones to typically identify up to 6 fertile days each cycle.