An ovulation calculator is something that apears on most pregnancy and baby sites on the internet. Searching for the term "ovulation calculator" on Google produces over 2 million results.

This "tool" is supposed to indicate when during a woman's menstrual cycle is the best time to try for a baby as there is supposedly a greater chance that you will be successful in this period.

Is there any evidence to suggest that using a calendar will increase the chance of a woman being pregnant as opposed to using common sense and logic?

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    Side note: The number of Google hits a search topic gets has nothing to do with its importance or value. Please see 9,000 Google hits can't be wrong - or can they?.
    – Kyralessa
    Commented May 8, 2011 at 5:25
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    @Kyralessa - I don't see where I matched prevalance to importance or value? My point was to go and see for yourself, rather than pointing to a specific example because they are so prevelant. That's why the first two sentences are together. Also, anyone who has had a baby would know that they are important enough that everyone sticks them on their site.
    – going
    Commented May 8, 2011 at 8:03
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    If common sense and logic suggest to use a calendar, there is no opposition. Commented May 31, 2011 at 4:56
  • Calculator or calendar?
    – LShaver
    Commented Dec 13, 2019 at 16:46

1 Answer 1


In order for conception to occur, there has to be an egg (or ova) present for the sperm to fertilize, where the 'average' woman will ovulate around day 14 (from the first day of the last menstrual period).

Of course, not every woman is average. Because the human ova is viable for a short period (~24 hours), knowing the right 'window' of time is helpful if you wish to become pregnant. The calendar method can (and often is) used in conjunction with basal body temperature measurements and the examination of mucus, and is based upon statistical analysis studies. Some calendars will show a fertility window for the next 3 months, allowing for more 'planning' of bedroom fun. (Vacation, honeymoon, etc)

I'll be honest, it's much easier for me to plunk down my information on a calendar, hit "ENTER" and get a nifty calendar in front of me for the next 3 months, than to pull out my desk calendar, find the first day of my last menstrual period, then count forward to when my next should arrive, then backwards again 14 days, then back another 4 days, etc....and to do that for the next three months? Call me lazy, I don't mind.

Common sense (and logic) says that if you want to get pregnant, you need to have sex. However, work, school, kids, and life in general can sometimes distract you - and having a calendar can give that extra 'nudge' in the right direction. (wink wink, say no more).

Is using the calendar the best option? No, charting BBT and purchasing an ovulation test are much more precise; however they aren't free - while an online calendar is. There are also women who aren't thrilled about taking and charting their temperature daily.

There are also women who utilize it for avoiding pregnancy - given the short lifespan of the ova, they know which days to avoid unprotected sex - this was called the rhythm method Current natural family planning methods utilize a similar approach, which avoids intercourse during the most fertile phase.

ETA: An overview of high vs low tech contraception

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    The article behind the last link endorses the rhythm method. This is highly misleading, since the rhythm method doesn’t work: even though the ovum is only viable for ~24h, sperm survives in the uterus much longer. Furthermore, reliably anticipating ovulation is much harder in practice than in theory. Failure rates for this method are unacceptably high compared to other methods of contraception, so this is not a reliable contraceptive measure under usual circumstances. Commented May 8, 2011 at 12:40
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    I never said it was a reliable method of birth control; merely that some women opt to use it.
    – Darwy
    Commented May 8, 2011 at 13:05
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    I am aware of that. But since your mention of the method was neutral and the only link you’re giving explicitly endorses the method this is misleading for uninformed readers. The 1993 article was heavily criticised in the scientific community because its conclusion is based on wrong information and flawed methodology and doesn’t stand up to scrutiny. Commented May 8, 2011 at 13:47
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    I'll edit to add in other similar results.
    – Darwy
    Commented May 8, 2011 at 18:20
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    @Konrad - as the old joke states, "what do you call people who practice rhythm method of Birth Control? ... Parents".
    – user5341
    Commented May 9, 2011 at 21:07

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