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Safe Days Calculator

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This safe days calculator helps you identify the infertile period in a woman’s menstrual cycle when the chances of pregnancy are lowest. By entering the date of the last menstrual period, average cycle length, and menstruation duration, it estimates safe days, fertile days, and ovulation. It can be used both for natural birth control and to plan conception.

Calculate Infertile and Fertile Days in Menstrual Cycle

Input Fields
If enabled, the result will update automatically when you change any value.

Safe and Fertile Days Estimation Formula

Formula
$$\text{Ovulation Date} = \text{LMP} + (\text{Cycle Length} – 14)$$

Fertile window: Ovulation date ± 2 days
Safe days: Before fertile window and after ovulation + 3 days.

The Safe Days Calculator is based on the calendar method and helps in identifying the high and low fertility phases of a woman’s menstrual cycle. It assumes that ovulation happens 14 days before the next period, and the fertile window spans several days around ovulation. By avoiding unprotected intercourse during this window, couples may reduce the risk of unplanned pregnancy. The tool is also helpful for those trying to conceive, by showing the most fertile days. Accuracy depends on cycle regularity.

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30 thoughts on “Safe Days Calculator

  1. shazamm says:

    I don’t like the new calculator it’s not accurate, i like the old one..fairly accurate on when will your next mestruation first day comes, why you fix something that’s not broken?
    if i set first day of menstruation is on 25-04-2025, menstruation duration is 5 day, and the cycle is 28, the result is… for the next month until november 2025, first day of mestruation will always be on 25th even if you change the cycle to 20 day.

    1. Wpcalc says:

      Thanks for your feedback. We fixed the calculator

  2. hmm says:

    hlo

  3. shazamm says:

    It’s accurate for me and my wife, i have use this since december 2023, if you want to avoid pregnancy, you can do it on green and gray colored dates but not on pink, red, orange and blue.

  4. 0719289083 says:

    What is meant by safe days to conceive

  5. 6374848353637737473 says:

    What does aafe days to concieve mean?