Our tips on how to calculate your most fertile days

One of the most effective ways to increase your chance of conceiving is to have unprotective sex when you’re most fertile. How are you supposed to know exactly when you're most fertile, we hear you ask? You may choose to use one of the many fertility calculator apps out there. However, if you wanted to work it out yourself, it's really not too difficult! 

 

I'm having regular periods

If you have regular periods, then you will know the length of your cycle. This is usually between 25 and 35 days. The average length is 28 days. Most women will ovulate 12-16 days before their period. The day of ovulation, the day after ovulation and the few days before this is the fertility window, and these are the only days in the month when you can get pregnant.

 

The calculation for regular periods – Example:

The first day of my last period was 1st October and I have a cycle of 28 days, meaning I expect my next period on 28th October. 14 days before my next period will be 14th October – this is the day I am likely to be ovulating. My most fertile days will therefore be the 10th through to the 15th October.

 

My periods aren't regular

If your periods are irregular, you can still calculate an approximate time of ovulation. To get pregnant it’s important that sperm is in the body when the egg is ready to be fertilised. You may have a 21 day cycle one month, then a 35 day cycle the next month and then a 28 day cycle the following month and this will make it difficult to know when you are likely to be ovulating.

 

The calculation for irregular periods - Example:

I’ve tracked my cycle for the past 6 months and it’s been 21 days, 35 days, 28 days, 22 days, 35 days and 35 days. By adding these together and dividing by 6 we can calculate the average cycle length (21 + 35 + 28 + 22 + 35 + 35 = 29.33 (29 days).

The first day of my last period was 1st October and to give me the best chance of conceiving I will open my fertility window to cover the shortest and longest length and have unprotected sex with my partner over a longer period of time than the 6 day fertility window that may be easier to highlight for a woman with regular periods.

The shortest cycle was 21 days so would have my period starting on the 21st October – 14 days before the 21st October is the 7th October. The longest cycle was 35 days and would have my period starting on the 4th October – 14 days before the 4th November is the 21st October. To give me the best chance of conceiving I will look to have unprotected sex with my partner regularly between the 3rd October (as we know sperm can live for several days) and 21st October.

Using your cycle length and date of last period is just one way to help you track your fertility window. You can also track your Basal Body Temperature, cervical mucus and ovulation pains. For more information about ovulation visit the NHS website here. We do strongly suggest that you meet with a healthcare professional if you have any questions or concerns about your health or fertility. 

Consider using a sperm-friendly lubricant

When you're aiming to make the most of your fertility window, it's difficult for calculations and timings not to get introduced into the bedroom. This makes sex less spontaneous and can result in a reduction of natural lubrication being produced.

For increased comfort (and pleasure), why not consider using a sperm-friendly lubricant? Standard lubricants can reduce your chance of conceiving but sperm-friendly lubricants create the ideal environment for reproduction, improving sperm mobility and helping the sperm track to the egg.