Ovulation Calculator

Trying to get pregnant? Use our calendar to find the best day to try to conceive and your most and least fertile days.

Your most fertile days

Your most fertile days are the 5 days leading up to ovulation and the day you ovulate. There's also a fertility hotspot - on your ovulation day and the two days just before.

When was the first day of your last period?

How long does your cycle usually last?

Not sure?

We'll calculate this based on the average cycle length of 28 days

How long is your luteal phase?

Not sure?

We'll calculate this based on the average luteal phase of 14 days

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  • How do I measure the length of my cycle?

    Start date is: the day you period normally begins. Finish date is: the day before your next period starts. The average is 28 days, and if you're not sure or you're irregular, our calculator will use 28 days. However, cycle lengths can generally range from 21 to 35 days. Chances are, you won't have an exact length, but choose the one that's most common for you.

  • What is my luteal phase?

    Bit of a strange term, but it means the second half of your menstrual cycle - when fertilisation and implantation can happen. It starts as you ovulate (when your ovaries release an egg) and finishes when your period starts. During your luteal phase, the lining of your uterus becomes thicker and your body temperature rises, creating the best conditions for a possible pregnancy. Typically, your luteal phase lasts between 10-16 days. If you're not sure, our calculator will use the average of 14 days.

  • So when should I have sex?

    Our Ovulation Calendar will show your 'fertile window', which is the best time to have sex if you want to conceive. This fertile window is 6 days long - 5 days before you ovulate and the day of ovulation. But wait! There's also a fertility hotspot within your window - 2 days before you ovulate and your ovulation day are your real 'go for it' days, when research suggests you have a 30% chance of getting pregnant. Cue the oysters…