Fertility calculator: fertile days and when you ovulate
Calculadora de días fértiles
Descubre cuándo ovulas y tus días más fértiles
Hello everyone, I’m back with an article that I think will interest all of you who are trying for a baby, and even those of you who, for now, would rather avoid it with natural methods (although, keep in mind, it’s a method without guarantees).
Today I want to talk about why it’s so important to know your fertile days: what they are, how to calculate them, which ovulation symptoms are most common and how ovulation tests work.
When do we enter the fertile days?
Statistically, few couples conceive on the first attempt: we’re talking about roughly 25%. 60% of couples take nine months to get pregnant. That’s why it’s so important not to stress out if it takes a while: stress can work against you when you’re trying.
When you’re trying for a baby, it helps a lot to understand how the menstrual cycle works. The cycle starts on the first day of your period and ends on the first day of your next one. A full cycle usually lasts an average of 28 days, although it can vary from woman to woman.
During your period, after your body sheds the endometrium (the tissue and blood that line the uterus), one of the follicles in your ovaries usually starts maturing, and it will be released around the middle of the cycle. That’s what we call ovulation. Once the egg is released around day 14, you’re in your fertile days.
Ovulation happens when the egg, under the influence of hormones, breaks free from the follicle. It then travels through the tube, crossing the surface of the ovary, in search of a sperm to fertilise it. Taking into account everything we’ve seen so far, and also that sperm can survive inside the body for up to 5 days (depending on quality), the fertile window covers the five days before ovulation plus the 12 to 24 hours after it.
A question we often ask ourselves is: “if I track my ovulation, is pregnancy guaranteed?” And the answer is no. Knowing exactly when you ovulate does NOT guarantee you’ll get pregnant if you have intercourse with your partner: many other factors come into play. But it definitely increases your chances a lot. Here’s a chart that sums up everything I’ve explained so far. The numbers at the bottom represent the first day of your period and show the development of the egg along with the changes in temperature and secretions.
How to calculate your ovulation date
So, in a normal menstrual cycle and allowing for possible margins of error, we can consider that from the tenth day after the first day of your period you enter the fertile period, which lasts until the nineteenth. The peak moment is ovulation itself, and that’s when you should enjoy plenty of relaxed sex with your partner, leaving behind the anxiety that can build up after trying for a while.
Try our ovulation calculator at the top of this page: enter the first day of your last period, your cycle length and your luteal phase, and it will tell you your ovulation day, your fertile window and your next period date — with a calendar showing your fertile days at a glance.
- First day of your last period + 10 days: your fertile period starts.
- First day of your last period + 19 days: your fertile period ends.
If your cycle is regular, this calculation is quite reliable. If it’s irregular, take it as a rough guide: in that case, ovulation tests (which I’ll tell you about below) will help you pinpoint things much better.
Ovulation symptoms
Many women don’t notice or don’t feel ovulation symptoms at all. I’m one of those who do. These are the most common ones:
- Lower abdominal pain: it happens during ovulation and is also known as mittelschmerz (from German, “middle pain”). It’s a sharp pain on one side of the lower abdomen, and it appears when the egg is released from the ovary.
- Rise in basal body temperature: you can measure your basal temperature every morning when you wake up. In the days before ovulation it dips slightly, and after ovulation it goes up.
- Cervical mucus: when your fertile days begin, you start producing secretions that become more liquid and elastic at the most fertile moment. Many of us know it as “egg white” discharge.
How does an ovulation test work?
Ovulation tests, although very effective, are a bit pricey and, from my point of view, they turn sex into something a little scientific and obligatory: the “it’s time today” thing. At the beginning of trying for a baby, it’s probably easier to calculate the approximate ovulation date with the steps above, or go by the sensations and symptoms I’ve described. Personally, I’d recommend ovulation tests when your periods are very irregular or when you’ve been trying for a long time (more than 12 months): that way you can check you’re not miscalculating your possible ovulation date, or whether you’re just not noticing the symptoms clearly. And, how does the ovulation test actually work? Ovulation tests, also called ovulation kits or LH kits, are based on the LH hormone, one of the hormones involved in the follicle rupturing and releasing the egg. Although there are conditions that can alter this hormone, as a general rule these ovulation kits are reliable about 99% of the time.
How to use an ovulation test
To use an ovulation test it’s very important to follow the instructions that come with the device, but basically it involves doing one test every day, starting a day or two before you expect ovulation. Testing on non-fertile days can be a significant waste of money, especially if you have to repeat it over several months. Doing the test between 10 in the morning and 8 in the evening should work properly, but it’s advisable to always do it at the same time.
Negative ovulation test
When the ovulation test is negative, don’t get discouraged: you simply have to do another one the next day. If too many days go by without a positive, or your period arrives, you’ll wait for the next cycle, maybe starting the first test a little earlier in case you’re calculating wrong. For my part, the times I used them, I started on the tenth day after the first day of my last period. If it keeps happening after several months, you should see a gynaecologist to find out what the problem might be.
Positive ovulation test
When the ovulation test is positive, it means ovulation will happen within the next 12 to 36 hours. So you can go ahead and enjoy sex freely with your partner (I insist: leave all worries behind), at least a few times over the next 4 days. And remember, you won’t need to do any more tests until your next period, if there’s no luck.
Frequently asked questions
Which days are the fertile days?
It depends on the length of your cycle, but in a 28-day cycle the fertile period runs approximately from day 10 to day 19, peaking around day 14 (ovulation). The fertile window includes the 5 days before ovulation and the 12-24 hours after it.
How long do the egg and the sperm survive?
The egg lives between 12 and 24 hours after ovulation. Sperm, on the other hand, can survive inside a woman’s body for up to 5 days. That’s why the fertile window is wider than many people think.
Is it possible to ovulate without any symptoms?
Yes, absolutely. Many women don’t notice either the pain or the changes in cervical mucus, and that doesn’t mean they’re not ovulating. If you want certainty, an ovulation test is the most reliable option.
When is the best time to take an ovulation test?
Between 10 in the morning and 8 in the evening, always at the same time, starting a few days before your expected ovulation date. That way you’ll avoid false negatives from testing too early.
What if my cycle is irregular?
Calculating fertile days is only a rough guide in that case. Ovulation tests are a great help for detecting the LH surge. And if you’ve been trying for more than 12 months without success (or more than 6 if you’re over 35), it’s a good idea to see a gynaecologist.
How does the ovulation calculator work?
Just enter the first day of your last period and your average cycle length (and optionally your luteal phase). The calculator estimates your ovulation date by subtracting the luteal phase from your cycle length, then works out your fertile window (the 5 days before ovulation plus the day itself). Remember it is an estimate: if your cycle is irregular, ovulation tests will give you more precision.
What is the difference between fertile days and ovulation?
Ovulation is the exact moment the egg is released from the ovary (a single day). Fertile days are the wider window: the 5 days before ovulation plus the 12-24 hours after, because sperm can survive up to 5 days waiting for the egg.
To wrap up, just remember that the best approach is regular sex, without stress, without rushing, with love and desire. And that’s all from me: if you’re trying for a baby, lots of encouragement and good luck ❤️.
And if you have any doubts about how the tests work, I recommend my article on how pregnancy tests work. When the time comes, remember you can take our free online pregnancy test to get some guidance from your symptoms. And if you fancy a bit of fun, try your luck with our fun fingerprint game — it’s just a game, not a real test.
Remember this article is for information only. If you’ve been trying for a while and something worries you, talk to your doctor or gynaecologist: nobody can guide you better than they can ❤️.
