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Luteal Phase Length Calculator

Work out your luteal phase length from ovulation and next-period dates (or cycle length), and see whether it falls in the typical 12–14 day range.

Calculate from

Ovulation date

First day of next period

Cycle length (cycle mode)

Ovulation cycle day (cycle mode)

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How it works

Luteal phase = days from ovulation to the day before the next period ≈ cycle length − ovulation day

The luteal phase runs from ovulation to menstruation and is driven by progesterone from the corpus luteum. Unlike the follicular phase it is fairly constant for each woman, usually 12–14 days. A phase under 10 days may not give an embryo time to implant; consistently short phases are one thing fertility clinics check.

Worked example

Ovulation 2 September, next period 15 September → 13-day luteal phase, typical.

Frequently asked questions

How do I know my ovulation date?

A temperature shift, positive ovulation test (ovulation about 24–36 h later) or a clinic scan. Apps that guess from cycle length can be off by several days.

Can a short luteal phase be treated?

Sometimes — progesterone support or ovulation medication — after tests confirm it. Discuss with a doctor rather than self-treating.

Related calculators

Ovulation Calculator

Find your estimated ovulation day, fertile window, peak days and next period from your last period and cycle length — with a luteal-phase setting, irregular-cycle range and a table of your next six cycles.

Menstrual Cycle Calculator

Map your menstrual cycle — period, follicular phase, fertile window, ovulation, luteal phase and likely PMS days — with today’s cycle day and phase, a luteal-phase setting and dates for your next six cycles.

Fertile Window Calculator

Find your fertile window, most fertile days and estimated ovulation date from your last period, cycle length and luteal phase, with the day-by-day chance of conception (Wilcox study), an irregular-cycle range and your next six cycles.

Educational estimate only — your midwife or doctor will confirm dates and advice for your pregnancy.