Fertility toolsFree and private
Ovulation CalculatorYour fertile window and the best days to try
Tell us when your last period started and how long your cycles usually are. You will see your fertile days for the next three cycles, the day you are most likely to ovulate, and what the chance of pregnancy looks like day by day. Nothing you enter leaves your phone.
- 6 Fertile days in every cycle
- 33 Percent best single day chance
- 3 Cycles planned ahead for you
- 0 Dates stored it all stays on your phone
Calculator
When are your fertile days?
Set your cycle, then tap the day your last period started. The calendar answers on the spot.
No date picked yet
Plan ahead
Your next three cycles
Shown for the example above. Tap your own date and all three months follow.
Pick the day your last period started and your next three cycles appear here, month by month.Pick my date
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1Cycle 1from 5 Nov 2026
- Period
- 5 Nov – 9 Nov
- Fertile window
- 14 Nov – 19 Nov
- Ovulation
- Thu 19 Nov
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2Cycle 2from 3 Dec 2026
- Period
- 3 Dec – 7 Dec
- Fertile window
- 12 Dec – 17 Dec
- Ovulation
- Thu 17 Dec
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3Cycle 3from 31 Dec 2026
- Period
- 31 Dec – 4 Jan
- Fertile window
- 9 Jan – 14 Jan
- Ovulation
- Thu 14 Jan
Your best days
The six days that matter most
Pregnancy can only start in these six days. The last three give you the best chance, so that is the time to try.
- Sat 14 Nov 10% Possible chance 5 days before
- Sun 15 Nov 16% Possible chance 4 days before
- Mon 16 Nov 14% Possible chance 3 days before
- Best day Tue 17 Nov 27% High chance 2 days before
- Best day Wed 18 Nov 31% Highest chance 1 day before
- Ovulation Thu 19 Nov 33% Highest chance Ovulation day
Simple rule: have sex every day or every other day in these six days. You do not need to time it to the hour.
Average chance from one day of sex, from a study of couples trying for a baby (Wilcox, NEJM 1995).
Signs of ovulation
Four signs you are about to ovulate
The calendar gives the likely days. These signs from your body confirm them.
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Look for this now
Clear, stretchy mucus
Clear and slippery, like raw egg white. It means your fertile days have started.
Around 14 Nov to 19 Nov
Check it each time you go to the toilet
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Look for this now
A positive LH test
A positive ovulation test means you will probably ovulate in the next 1 to 2 days.
Around 17 Nov to 18 Nov
Test once a day from a few days before
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Look for this now
A twinge low in your tummy
A brief ache on one side of your lower tummy, right around ovulation.
Around 18 Nov to 20 Nov
Note which side, it can switch each month
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Look for this now
A small rise in temperature
Your morning temperature goes up a little once ovulation has happened.
Around 20 Nov to 2 Dec
Measure before you get out of bed
Trying for a while?
When it is time to talk to a fertility specialist
Most couples conceive within a year. If it is taking longer, a specialist can find out why, and many causes are simple to treat.
- Under 35after 12 months of regular sex without contraception
- 35 or olderafter 6 months of trying
- Straight awayif your periods are very irregular or have stopped, if you have PCOS or endometriosis, or if either of you has a known fertility concern
Questions
What people ask about ovulation
Straight answers to the questions we hear most. Something else on your mind? Our specialists are happy to talk it through.
Ask a specialist-
01When am I most likely to get pregnant?
In the six days that end on the day you ovulate, and most of all in the last three. Sperm can live for up to five days, while an egg lives for about a day, so sex in the days before ovulation gives the best chance.
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02How is ovulation worked out?
Ovulation usually happens about 14 days before your next period starts. With a 28 day cycle that is around day 14; with a 32 day cycle it is around day 18. The calculator counts forward from the first day of your last period using your usual cycle length.
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03What if my cycles are irregular?
Switch on "My cycles vary" and add your shortest and longest cycle from the past few months. The calculator then gives a wider window that covers both, which is more honest than a single date. Ovulation test strips help you narrow it down.
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04What are the real chances of pregnancy each day?
In a well known study of couples trying to conceive, the chance of pregnancy from sex on a single day rose from about 10 percent five days before ovulation to about 33 percent on the day itself. These are averages; age and health change them for each person.
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05Can I use this calculator to avoid pregnancy?
No. Cycles shift from month to month, and a calendar estimate is not reliable enough for contraception. Please talk to a doctor about a method that suits you.
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06How long should we try before seeing a specialist?
See a fertility specialist after 12 months of regular unprotected sex if you are under 35, or after 6 months if you are 35 or older. Go sooner if your periods are very irregular or absent, if you have PCOS or endometriosis, or if either partner has a known fertility concern.
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07Is my information stored anywhere?
No. The calculation happens in your own browser. The dates you enter are never sent to us, never saved and never added to the page address.
We are here when you need us
Timing helps. So does the right person on your side.
If you have been trying for a while, one conversation with a specialist can tell you far more than a calendar ever will.