Ovulation Calculator

Ovulation typically occurs 12 to 16 days before the start of your next period, which for a 28-day cycle means around day 14. The fertile window spans approximately six days, made up of the five days before ovulation, since sperm can survive that long in fertile cervical mucus, plus the day of ovulation itself, when the egg lasts 12 to 24 hours. Counting starts from day 1, the first day of bleeding, rather than the day the period ends.

This calculator estimates your ovulation day and fertile window based on your cycle length and the first day of your last period. For regular cycles it counts back 14 days from the expected next period. For irregular cycles it gives a broader estimated range and recommends additional tracking methods. Cycle length moves the date without changing the rule, so a 21-day cycle puts ovulation around day 7 or 8, a 28-day cycle around day 14, and a 35-day cycle around day 21 or 22.

Your body gives several signals worth learning. Cervical mucus turns clear, slippery and stretchy, much like raw egg white, and is the most reliable physical sign. Basal body temperature dips slightly beforehand then rises by 0.2 to 0.5°C afterwards, which confirms ovulation has happened rather than predicting it. Between 20 and 30% of women feel Mittelschmerz, a one-sided twinge low in the abdomen. Breast tenderness, higher libido and occasional light spotting round out the list.

The NHS advises that the most accurate way to confirm ovulation is with ovulation predictor kits (OPKs), which detect the LH surge 24 to 36 hours before ovulation. A pack of 10 to 20 tests costs £8 to £25. Basal body temperature tracking and cervical mucus monitoring can also help, and two methods used together beat any one on its own. Tracking apps such as Flo, Clue and Natural Cycles have grown steadily more accurate at predicting the window from your own recorded data.

Having sex every one or two days through the fertile window gives sperm time to replenish while covering the days that matter most, namely the two or three days before ovulation and ovulation day itself. In a 28-day cycle that points at days 11 to 14. No sexual position has been shown to make any difference. Many ordinary lubricants are spermicidal, so a sperm-friendly product such as Pre-Seed or Conceive Plus is the safer choice. Keeping BMI between 18.5 and 25, stopping smoking, limiting alcohol and managing stress apply to both partners.

Folic acid at 400 micrograms a day is recommended from three months before conception, rising to 5 mg for anyone with a BMI of 30 or above, diabetes, or a family history of neural tube defects. If you have been trying to conceive for 12 months, or 6 months if you are over 35, the NHS recommends speaking to your GP. First-line tests are a semen analysis, blood tests and an ultrasound scan, with referral to a fertility clinic if there is still no pregnancy after 18 to 24 months.

About 1 in 7 UK couples experience difficulty conceiving. Ovulation disorders such as PCOS and premature ovarian insufficiency, tubal damage from endometriosis or infection, male factor problems in 30 to 40% of cases, and age all feature, with female fertility falling sharply after 35 and male fertility after 50. PCOS is often treated on the NHS with metformin or clomiphene citrate. NHS IVF offers up to 3 cycles to women under 40 who meet the criteria, which include a BMI of 19 to 30, both partners being non-smokers, neither having a child from a previous relationship and 2 or more years of trying, although many areas now fund only one cycle. Privately a cycle costs £4,000 to £8,000, and a full course often reaches £15,000 to £30,000.