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Ovulation calculator

Trying for a baby? Use our ovulation calculator to estimate your most fertile days and boost your chances of getting pregnant.

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How does the ovulation calculator work?

The ovulation calculator uses the date of your last period and your average cycle length to estimate your fertile window — the days when you're most likely to conceive. Ovulation usually happens about 14 days before your next period. By predicting this window, the tool helps you time sex or insemination for the best chance of success.

Tip: Having sex every 2–3 days throughout your cycle can also help ensure sperm is always available when ovulation occurs.

What if my periods are irregular?

Irregular periods can make it harder to predict ovulation with a calculator alone. If your cycles vary significantly from month to month, consider:

  • Using ovulation predictor kits (which detect hormone surges in urine)

  • Tracking cervical mucus changes (it becomes clearer and stretchier around ovulation)

  • Monitoring basal body temperature (a slight increase signals ovulation has occurred)

If you're concerned about irregular periods, speak to your GP.

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How will I know if I am ovulating?

Signs you may be ovulating include:

  • A change in vaginal discharge — becoming clearer, slippery, and stretchy

  • Mild pelvic or abdominal pain

  • A slight rise in basal body temperature

  • Increased sex drive or heightened senses (such as smell or taste)

Using a combination of these signs alongside a calculator or ovulation test can improve accuracy.

How else can I increase my chances of getting pregnant?

Improving your general health can support fertility. You can try:

  • Maintaining a healthy weight – being under-or overweight can affect ovulation

  • Taking folic acid before conception

  • Avoiding smoking, excess alcohol and caffeine

  • Managing stress, which can impact hormone balance

If you've been trying to conceive for over a year (or six months if over 35), consider seeking medical advice.

Article history

The information on this page is written and peer reviewed by qualified clinicians.

  • 15 Jul 2025 | Originally published

    Authored by:

    Patient infomatics team

    Peer reviewed by

    Patient infomatics team
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