Ovulation window calculator

Pick dates then calculate

    Due date Percentage Compound
    GuideUnderstanding Due-Date and Ovulation Estimates

    Learn how calendar-based pregnancy and ovulation estimates are calculated and why individual timing varies.

    Read guide →
    Pregnancy Due Date Calculator

    Frequently asked questions

    How do you estimate ovulation
    Typical ovulation occurs cycle length minus luteal phase after LMP.
    What is fertile window
    A range of days around ovulation with higher chances of conception.
    Is this medical advice
    No.
    Can I change luteal phase
    Yes, adjust the input.
    What if cycles are irregular
    Use with caution, consult a professional.
    Do you store data
    No.
    Can I share a screenshot
    Yes, use the screenshot button.
    Do you support reminders
    Not in this version.
    Is the tool free
    Yes.
    What browsers are supported
    Modern browsers on mobile and desktop.
    What does the Ovulation Window Calculator do?
    Estimate likely ovulation and fertile-window dates from cycle dates and typical cycle length.
    How should I interpret a Ovulation Window Calculator result?
    Read the displayed labels and validation messages together, then verify important findings against the original source. The result is a practical aid, not proof beyond the data it can inspect.
    What can affect the Ovulation Window Calculator result?
    Inputs, source data, network conditions, and the limits explained on the page can affect the result.
    Where can I learn more about using the Ovulation Window Calculator?
    Read “Understanding Due-Date and Ovulation Estimates” for a practical workflow, limitations, and checks to make after using the tool.