Cervical mucus changes
Most reliable at homeDischarge turns clear, slippery and stretchy, like raw egg white, in the days before ovulation. It is the single most useful sign you can read without a device.
Tools & Calculators
Six days a month
actually count.
Ovulation is one day, but the fertile window is six: the five days before the egg is released, plus the day itself. Sperm can wait; the egg cannot. Enter the first day of your last period and this works out exactly when those days fall for you.
The short answer
Ovulation happens about 14 days before your next period starts, not 14 days after the last one began. So on a 28 day cycle it falls around day 14, and on a 32 day cycle around day 18. Your fertile window is the five days before ovulation plus ovulation day. The best odds are the two days immediately before release, at roughly 25 to 30 percent per cycle.
- The formula
- Cycle length minus luteal phase, counted forward from day one of bleeding
- Why the window opens early
- Sperm survive up to 5 days; the egg lasts only 12 to 24 hours
- Best sign at home
- Clear, stretchy, egg-white cervical mucus in the days before release
- When to get seen
- 12 months trying under 35, 6 months at 35 to 39, 3 months at 40 and over
Your window, in one view
Tap the day your last period started. Everything else moves with it. Nothing is sent anywhere and nothing is stored.
Clinical reference: ASRM, Optimizing natural fertility. Calendar estimates cannot confirm ovulation and are less reliable with irregular cycles.
September 2026
Tap any day to set day one
Shaded days are calculated from a 28 day cycle with a 14 day luteal phase.
Your cycle, phase by phase
The day ranges below move with the cycle length you set. The phase you are in right now is marked.
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Menstrual
The lining sheds. Bleeding usually lasts three to seven days, and day one of bleeding is day one of the cycle.
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Follicular
Follicles mature in the ovary and oestrogen climbs. The lining rebuilds. This is the phase that stretches or shortens when a cycle is long or short.
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Fertile window
The six days that matter: the five before ovulation plus the day itself. Sperm survive up to five days in fertile cervical mucus, which is why the window opens before the egg does.
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Ovulation
An LH surge releases the egg, roughly 24 to 36 hours after the surge begins. The egg is viable for 12 to 24 hours.
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Luteal
Progesterone rises to hold the lining. This phase is the steady one, almost always 12 to 16 days, whatever the total cycle length.
What your hormones are doing
Which day is worth the most
Chance of conceiving from intercourse on each day of the window. Population averages, and the shape is what matters, not the decimal.
4%
5 days before
12%
4 days before
20%
3 days before
25%
2 days before
30%
1 day before
25%
Ovulation day
8%
1 day after
2%
2 days after
The window opens five days before release because sperm survive that long in fertile mucus. It shuts almost immediately after, because the egg does not. Covering the window with sex every one to two days beats trying to land on a single date.
The next three cycles
Projected forward on the same cycle length. Re-enter your dates each month, because a real cycle rarely repeats to the day.
| Cycle | Period starts | Fertile window | Peak two days | Ovulation | Test from |
|---|---|---|---|---|---|
| This cycle | Fri, 11 Sep | Sun, 20 Sep to Sat, 26 Sep | Wed, 23 Sep to Fri, 25 Sep | Fri, 25 Sep | Fri, 9 Oct |
Six signs you are ovulating
A calendar predicts. These report. Where the two disagree, believe your body.
A positive LH test
24 to 36 hours warningOvulation predictor kits detect the luteinising hormone surge that triggers release. A positive means ovulation is likely within a day and a half, so it tells you the window is open now.
Basal body temperature rise
Confirms after the factWaking temperature rises by roughly 0.3 to 0.5 degrees Celsius after ovulation and stays up. It confirms that you ovulated, but only once the window has closed.
Mittelschmerz
About 1 in 5 womenA one-sided twinge or dull ache low in the abdomen, lasting minutes to a day or two. Useful if you get it consistently, meaningless if you do not.
Higher libido
Soft signalDesire tends to peak in the two days before ovulation, tracking the oestrogen rise. Real, but too variable to time anything by on its own.
Breast tenderness or spotting
Soft signalLight mid-cycle spotting and breast sensitivity follow the hormone swings around release. Worth noting in a tracker, not worth planning around.
What helps, and what does not
The advice that survives contact with the evidence, on both sides of the ledger.
Do
- Track three full cycles before you trust a dateOne cycle tells you almost nothing. Three tells you your real average and how much it varies.
- Have sex every one to two days across the whole windowCovering the window beats trying to hit a single day. Daily and alternate-day both work.
- Start folic acid before you conceive, not after400 micrograms daily, from at least one month before conception, to lower the risk of neural tube defects.
- Read your cervical mucus alongside the datesThe calculator predicts. Mucus reports what your body is actually doing this cycle.
- Use an LH kit if your cycles vary by more than a few daysIt replaces a guess with a measurement, and it costs very little.
- Keep weight, sleep and alcohol in a sensible rangeA BMI well outside 19 to 30, chronic short sleep and heavy drinking all disturb ovulation.
Do not
- Do not rely on dates alone if your cycles are irregularIf your cycle length swings by more than seven or eight days, a calendar prediction is close to guesswork. Get the irregularity looked at.
- Do not save up sperm for the fertile windowLong abstinence lowers motility. Regular ejaculation through the cycle produces better samples than stockpiling.
- Do not use ordinary lubricant while tryingMost lubricants slow or kill sperm. If you need one, use a product specifically labelled fertility friendly.
- Do not smoke or vape, and do not sit in the heatSmoking brings menopause forward and damages egg and sperm quality. For men, saunas and hot tubs suppress production for weeks.
- Do not over-trainVery high training loads with low body fat can stop ovulation altogether. Moderate exercise helps; extreme exercise does not.
- Do not treat a missed window as a failed monthEven with perfect timing, a healthy couple has roughly a one in four chance in any given cycle. Most conceptions take several tries.
When to stop tracking and get seen
Tracking is worth doing. Tracking for years while something treatable goes unfound is not.
Under 35
After 12 months
Trying for a year with regular unprotected sex and no pregnancy is the point at which investigation is warranted.
35 to 39
After 6 months
Egg quality and quantity fall faster from the mid thirties, so the waiting period halves.
40 and over
After 3 months
Do not wait out a full year. Testing early keeps more options open.
Any age
Straight away
If any of the flags below apply, book without waiting out a trying period at all.
Book straight away if any of these apply
- Periods that are absent, or arrive more than 35 days or less than 21 days apart
- A cycle length that swings by more than seven or eight days month to month
- A known diagnosis of PCOS, endometriosis, fibroids or thyroid disease
- Two or more miscarriages
- Previous pelvic surgery, an ectopic pregnancy or pelvic infection
- A known problem on the male side, or a previous abnormal semen analysis
- Past chemotherapy, radiotherapy or pelvic surgery for either partner
- Severe period pain or pain during sex that disrupts normal life
Where this calculator stops working
It is arithmetic on an assumption. Here is where the assumption breaks, stated plainly rather than buried.
Irregular cycles
The maths assumes a luteal phase of fixed length subtracted from a predictable cycle. If your cycle length moves around, so does the answer.
PCOS
Ovulation may be late, unpredictable or absent. Dates are unreliable here and an LH kit can read falsely positive.
Coming off the pill
It can take one to three cycles for ovulation to settle into a rhythm you can predict.
Breastfeeding
Prolactin suppresses ovulation, and the first ovulation after birth arrives before the first period, with no warning.
Illness, travel and stress
A fever, a long-haul flight or an acute stress can delay ovulation in that cycle by days.
Perimenopause
From the early forties, cycles shorten and then scatter. Prediction by calendar loses its footing.
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1
Find day one
Day one is the first day of proper bleeding, not spotting. Enter that date.
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2
Enter your cycle length
Count from day one of one period to the day before the next. Use your average over three cycles.
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3
Read your window
The calculator returns your ovulation date, the six fertile days around it, and the day a test becomes meaningful.
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4
Confirm with your body
Check the dates against cervical mucus and, if cycles vary, an LH kit. Adjust the cycle length next month.
Ovulation questions, answered straight
01 How do I calculate my ovulation date?
Subtract the length of your luteal phase from your cycle length, then count that many days forward from the first day of your last period. The luteal phase is close to fixed at about 14 days for most people, so on a 28 day cycle ovulation falls around day 14, and on a 32 day cycle around day 18. It is the follicular phase before ovulation that stretches or shortens, not the luteal phase after it.
02 When am I most fertile?
The two days immediately before ovulation. Intercourse on the day before ovulation carries roughly a 30 percent chance of conception, and two days before roughly 25 percent, compared with about 4 percent five days before. The full fertile window is six days: the five days before ovulation plus ovulation day itself.
03 How many days after my period do I ovulate?
On a 28 day cycle, ovulation usually falls about nine days after a five day period ends, which is day 14 of the cycle. On a longer cycle the gap is bigger and on a shorter cycle smaller, because the phase before ovulation is the part that varies. Counting from day one of bleeding is more reliable than counting from the day your period stops.
04 Can I get pregnant right after my period?
Yes, and it is more common than people expect. Sperm survive up to five days in fertile cervical mucus, so sex towards the end of a period can still meet an egg released early, especially on a short cycle of 21 to 24 days where ovulation can arrive around day 8 or 9.
05 How long does the egg survive after ovulation?
Twelve to twenty four hours. That short window is why the fertile days sit before ovulation rather than after it: sperm can wait for the egg, but the egg cannot wait for sperm.
06 What if my cycles are irregular?
A calendar prediction assumes a cycle length it can rely on. If yours swings by more than seven or eight days, treat the dates as a rough guide only and confirm with ovulation predictor kits and cervical mucus. Persistently irregular cycles, or cycles shorter than 21 days or longer than 35, are worth investigating rather than working around.
07 How accurate is an ovulation calculator?
For someone with regular cycles it usually lands within a day or two, which is close enough because the fertile window is six days wide. It is far less reliable with irregular cycles, with PCOS, in the first cycles after stopping hormonal contraception, while breastfeeding, and in perimenopause. It is a planning tool, not a test.
08 How often should we have sex to conceive?
Every one to two days across the fertile window. Daily and alternate day intercourse produce similar pregnancy rates, and both beat trying to pinpoint a single day. Saving up sperm for the window is counterproductive, because long abstinence reduces motility.
09 Can I ovulate without getting a period?
Yes. Ovulation comes first and the period follows about two weeks later, so it is possible to ovulate and conceive before any period returns, which is why pregnancy can happen while breastfeeding or after a long gap. The reverse also happens: you can bleed in a cycle where no egg was released.
10 When should I see a fertility specialist?
After twelve months of trying if you are under 35, six months if you are 35 to 39, and three months if you are 40 or over. Come sooner, without waiting out a trying period, if your periods are absent or irregular, if you have known PCOS or endometriosis, if you have had two or more miscarriages or previous pelvic surgery, or if there is a known problem on the male side.
Next step
Tracked for months and still nothing?
That is exactly when a consultation earns its keep. Bring your cycle chart. Dr. Kavita Manchanda will read it against your history and tell you whether the timing is the problem, or something else is.