how to use a fertility calculator - new lune

How To Use A Fertility Calculator

If you’re trying to get pregnant, then you need every advantage on your side. Even couples in perfect reproductive health can find they’re waiting longer than they’d like for a positive result on the pregnancy test, because fertility is essentially a game of chance.

Your fertility, as measured by doctors, is really an expression of the odds you will get pregnant in a given period of time. All sorts of things can effect your fertility, from environmental factors, to your age (though research shows this is a less dramatic factor than received wisdom would have us believe), state of health, diet and even level of stress.

One of the advantages you could have in your corner is a fertility calculator: a tool or app that, with a bit of data provided by you, can predict when you will be fertile. Today we’re taking at a look at these and finding out what they are and how you can use them.



Getting pregnant is deeply linked to when you ovulate. Ovulation is the event in your menstrual cycle when your ovaries release a mature, fertile egg, ready to encounter sperm and, potentially, be fertilised, beginning its development into an embryo.

It’s ovulation that your fertility calculator is really telling you about. You’re at your most fertile in the five days before and one day after you ovulate – as sperm can survive five days in the body after sex and the egg remains viable for 24 hours after ovulation.



The most basic apps and online pages only ask for two pieces of information: the date of your last period, and the length of your menstrual cycle. They then use a database of women’s menstrual cycle data to match your data with a profile and tell you when women with that profile are fertile.

More complicated fertility calculators ask for more data but provide more accurate results. Some will ask for information like your age, weight and background health conditions while even better ones will accept the results from an ovulation test kit or the results of your BBT tracking.

Even better fertility calculators might come linked to the tests they take data from. Rather than relying on you taking readings with a digital thermometer and entering them in an app – providing multiple ways for human error to distort your prediction – a sensor can relay your temperature direct to the cloud where your results can be produced and a prediction pushed to your phone, so you have a better chance of getting pregnant when you want to.



xo N

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This is a contributed post.

  1. If one goes the more accurate route, they should also make sure that the company they’re deal with is not data mining their information and selling it. Medical information is big money nowadays. Everybody from big Pharma and insurance to baby supplies manufacturers wants to know if you’re trying to get pregnant.

    Another good article though, even if you forgot the alternative of LOTS and LOTS of sex. 😀 LOL

  2. Thanks for liking my last post, N! 💓 It’s spring and quarantine, there must be lovemaking and babies on the global brain lol!

    I agree with what Silk Cords said; I don’t use tracking apps much anymore for that same reason. There is a great book I love to recommended, also for natural birth control, called Taking Charge of Your Fertility, by Toni Weschler. Even for those who never plan on having children. The book helps one do exactly what the title says, along with give knowledge of our amazing bodies.

    I always love your beautiful post presentation, formatting and topics! And love that you support fellow bloggers, and that you allow comment discussion. I know it takes time and energy, but it’s much appreciated, thank you. 🙏💛

    1. My pleasure love! Haha definitely 😂 Ohh I’ll definitely check it out, thanks for the recommendation!

      Aww thank you so much! You are the sweetest 💛

  3. Knowing my cycle was key to conceiving our child! I took my oral temperature every day before eating, drinking, etc. for three years. I used a very accurate basal thermometer. There is a slight raise in temperature during ovulation. As a result, every month I knew my fertile days. That was central to our success.

    1. Thanks, I felt very connected with my cycle charting my temperature first thing each morning. I knew its exact length and when the golden window was. I highly recommend it! Very empowering.

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