Ovulation calculator
This estimates when you are likely to ovulate and the days you are most fertile, using your own cycle length.
Your details
Ovulation is most likely around
Fri 30 October 2026
an estimate: bodies vary
- Most fertile days25 Oct to 30 Oct
- Next cyclearound 27 Nov
- Cycle length used28 days
- Start ovulation testscycle day 12, 27 Oct (about 17 days before your cycle ends)
This counts 14 days back from your next expected period. Ovulation tests, cervical mucus changes and temperature tracking give a better personal picture. Contraception should never be based on a calendar estimate.
Trying for a year without success (6 months if you are 36 or over) is a good time to see your GP. Sooner if you have irregular periods or a known condition.
The working
Fourteen days back
The time from ovulation to the next period is fairly steady at about 14 days. So with a 28 day cycle starting 1 October, ovulation is likely around 15 October, and the fertile days run from 10 to 15 October. With a 32 day cycle it moves to about 19 October.
Ovulation tests and varying cycles
When to start testing
Most ovulation test leaflets say to start about 17 days before your next period is due, so cycle day 12 in a 28 day cycle. If your cycles vary, count from your shortest one so you do not miss an early surge. Ovulation usually follows a positive test within a day or two.
Large app studies show the day of ovulation moves more than the 14 day rule suggests, even in regular cycles. With cycles of 26 to 32 days starting 16 October, ovulation could fall anywhere from 28 October to 3 November, so we show that range too.
Signs to look for
Your body's clues
- Clear, slippery, stretchy mucus, like raw egg white
- A small rise in temperature after ovulation
- Ovulation test strips turning positive a day or so before
- Some people feel a twinge on one side
Making it simple
The NHS view
The NHS suggests sex every 2 to 3 days throughout the cycle, which covers the fertile days without timing pressure. Folic acid (400 micrograms a day) is advised from when you start trying until 12 weeks of pregnancy.
Read with care
What this cannot tell you
- Exact dayOvulation can shift, even in regular cycles.
- Fertility problemsThis cannot tell you whether you are ovulating.
- ContraceptionCalendar estimates are not a reliable method.
Questions
Common questions
When do I ovulate?
About 14 days before your next period, so day 14 of a 28 day cycle.
How many days am I fertile?
About 6 days: the 5 before ovulation and the day itself.
Can I get pregnant on my period?
It is unlikely but possible, especially with short cycles.
Sources
- NHS: trying to get pregnant
- Wilcox AJ et al. Timing of sexual intercourse in relation to ovulation. N Engl J Med 1995
- NICE CG156: fertility problems, assessment and treatment
- Bull JR et al. Real-world menstrual cycle characteristics of more than 600,000 menstrual cycles. NPJ Digit Med 2019
Last checked 21 October 2026. Spotted something wrong? Tell us and we will fix it.
Support when you need it
Contact your midwife or GP any time you are worried, and call NHS 111 if you cannot reach them. If a date or a result brings up difficult feelings, Tommy's and the Miscarriage Association offer kind, free support.
Related
Related calculators
- Fertile window calculatorYour next three fertile windows.Open
- Period calculatorYour next three periods, from your last one.Open
- Conception calculatorWhen conception probably happened.Open
- Cycle length calculatorAverage cycle and how much it varies.Open
- Due date calculatorEstimated due date from the first day of your last period.Open
- Fertility appointment countdownDays to your clinic visit, and the cycle day.Open