< How it Works

Based on Averages

Cycle evaluation based on averages is a simple but powerful way to monitor your fertility and to predict future cycles. It will tell you when to expect ovulation, show you when you are most likely fertile or infertile, as well as estimating when to expect your next period.

How it Works

The determination of your fertility as well as the prediction of future cycles are based on simple principles: the overall average length of your cycle and your average luteal phase to determine the day of ovulation. Lily will display the different phases of fertility in different colors to make it easier to spot where you are in each given cycle and to time conception as well as knowing when to protect or avoid if you are not looking to get pregnant.
The predictions will become more accurate the more you chart. The settings allow you to slightly adjust a few values used for evaluation, in case you deem it necessary.

Please Note

Lily's averages-based cycle evaluation method is best suited for women with regular cycles with a length of roughly 29 days. If you know from experience that your cycles tend to greatly differ in length, we recommend that you use Lily's symptoms-based evaluation method instead. Instead of relying on averages, symptoms-based evaluation takes your basal body temperature and cervical mucus quality and evaluates your cycles as you go along, giving you one of the most accurate fertility evaluations available today.


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We do not guarantee the method of birth control or pregnancy achievement as described on this web site.

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