How to Track Ovulation: Every Method Compared

Do you need to track ovulation at all?

Not necessarily. NICE, which sets guidance for the NHS in England, says vaginal sex every 2 to 3 days optimises the chance of pregnancy, and that people with regular monthly cycles are likely to be ovulating. Sex at that frequency covers the fertile window without pinpointing it. In the US, the American College of Obstetricians and Gynecologists (ACOG) frames it the other way round: identify your fertile days and have sex every day or every other day during them.

Tracking does have measurable value. A 2023 Cochrane review of seven trials (2,464 women or couples) found that timing sex with urine ovulation tests probably increases the chance of a live birth in women under 40 who have been trying for less than a year: if the chance without testing is 16%, with testing it is 16% to 28%. For fertility awareness methods such as charting temperature and mucus, the evidence was too limited to say. It also lists downsides: stress, time and the cost of kits and app subscriptions.

It makes most sense if you want to learn your pattern or concentrate sex around your fertile days, and for insemination, which NICE says should be timed around ovulation.

Ovulation tracking methods compared

Some methods warn you before ovulation, which is what you need to time sex; others only confirm it afterwards. Accuracy ratings come from a 2017 review by Su and colleagues in Bioengineering & Translational Medicine, drawing on different, mostly small studies: read them as a ranking, not a score.

Calendar and app predictions

Counting days predicts from the past. ACOG's Standard Days method treats days 8 to 19 as fertile, and it works best if your cycles are regular and consistently 26 to 32 days long. In a study of 696 cycles, Allen Wilcox and colleagues found the fertile window fell entirely within days 10 to 17 in only about 30% of women, and warned that its timing "can be highly unpredictable, even if their cycles are usually regular". Apps that only use your period dates share that limit; fertility apps and wearables also covers rings and other temperature-sensing devices. The ovulation and fertile window calculator gives a first estimate on the same basis.

Cervical mucus

Just before ovulation, ACOG says, the amount of mucus noticeably increases and it becomes thin and slippery; just after, it decreases and thickens. Because the change comes first, ACOG suggests sex every day or every other day while thin, slippery mucus is present. Details: understanding cervical mucus.

Basal body temperature

Your resting temperature rises after ovulation, by 0.5 to 1°F (roughly 0.3 to 0.6°C) according to ACOG, and stays up until your period. ACOG says charting can confirm ovulation but cannot predict it. NICE goes further: do not use temperature charts to confirm ovulation, because they do not reliably predict it. In one study in Su's review, temperature placed ovulation within a day of the LH surge in only 17 of 77 cycles. It is best for learning your pattern over several cycles: basal body temperature charting.

Ovulation tests (LH kits)

Urine tests detect the surge of luteinising hormone (LH) that triggers ovulation, and ACOG says a positive result suggests ovulation in the next 24 to 48 hours. Su notes that pregnancy rates from a single act of sex are highest from 2 days before ovulation to the day itself, which points to the day of a positive test and the day after. They have the best trial evidence of any home method. The limits: LH surges vary in shape, and two women in one study of 43 had a surge without ovulating. More: ovulation predictor kits.

Ultrasound follicle tracking

A transvaginal scan can watch the dominant follicle grow and then shrink once it has released the egg. Su describes this as the standard reference for detecting ovulation, used mainly in assisted reproduction, and ACOG lists ultrasound among fertility tests that can predict when ovulation will occur. It means repeated clinic visits, and Cochrane found no trials of timing sex by ultrasound.

Progesterone blood test

This is how doctors confirm ovulation. NICE recommends a progesterone blood test in the mid-luteal phase, day 21 of a 28-day cycle, for anyone being investigated for infertility, even with regular cycles. With long irregular cycles it may need to be later, for example day 28 of a 35-day cycle, and repeated weekly until the next period. ACOG describes it as taken about 1 week before you expect your period. It tells you that you ovulated, not when. See fertility tests explained.

What are the signs of ovulation?

• Wetter, slippery mucus in the days before ovulation (ACOG).
• A positive LH test, 24 to 48 hours before (ACOG).
• A one-sided ache or twinges low in the tummy for some people: see ovulation pain.
• A temperature rise that only shows once ovulation has happened (ACOG).

None of these proves an egg was released: Su notes that a normal LH surge, working corpus luteum and period with no egg released has been reported in 10.7% of cycles in normally fertile women. Ultrasound, which shows the follicle collapsing, is the reference standard.

Tracking ovulation with irregular periods or PCOS

The NHS says irregular periods can make getting pregnant harder because you might not ovulate regularly, and says sex every 2 or 3 days throughout your cycle can help. Calendar methods suit regular cycles, and Su notes that few studies of ovulation-detection methods included women with irregular cycles. Su also lists polycystic ovary syndrome (PCOS) among conditions that can throw LH tests and temperature charts off. If your cycles are long, NICE's progesterone test is timed later and repeated weekly. See irregular periods and conceiving.

When to see a GP

The NHS says to see a GP if your periods are irregular, meaning a gap of less than 21 or more than 35 days, or if they are irregular and you are struggling to get pregnant; you may be referred for tests. For how long to try first, see when to see a doctor about fertility.

Frequently asked questions

How long does ovulation last?

The release of the egg is a single event, and ACOG says the egg survives about 24 hours afterwards. Because sperm survive for several days, ACOG puts the fertile window at 5 days before ovulation to 1 day after. That is why the advance signals, mucus and LH tests, matter most for timing sex.

When does ovulation occur?

In an average 28-day cycle, about 14 days before your next period, according to ACOG. It does not reliably fall on day 14, because the first half of the cycle varies: Wilcox's study found the fertile window entirely within days 10 to 17 in only about 30% of women. So estimates count back from your next period, not forward.

How can you track ovulation at home?

The home options are cycle dates, cervical mucus, basal body temperature, urine LH tests, fertility monitors and saliva tests. In Su's 2017 review, urine LH tests rated highest for accuracy at 97%, mucus moderate and temperature low. ACOG describes combining temperature and mucus as the symptothermal method.

Can you track ovulation without a period?

Calendar methods cannot, because they count from your period. The NHS says that with irregular periods you might not ovulate regularly, and lists pregnancy, hormonal contraception, weight change, stress and too much exercise among common causes. If your periods have stopped, take a pregnancy test and see a GP before relying on any tracking method.