Luteal Phase Calculator

Work out your luteal phase length from your cycle length and ovulation day. A luteal phase of 10 to 16 days is typical. Example: a 28-day cycle with ovulation on day 14 has a luteal phase of 14 days.

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Cycle length (days)

Day of cycle you ovulated (from OPK or temperature)

How to use the Luteal Phase Calculator

Enter the values in the fields.
Press Calculate to see the result with the steps shown.

Formula and method

Luteal phase length = cycle length – day of ovulation. Follicular phase = day of ovulation – 1.

Luteal phase lengths

Length	Meaning
Under 10 days	Short; may reduce chance of implantation
10 to 16 days	Typical; average about 12 to 14
Over 16 days	Long; check for pregnancy

Cycle length and ovulation day

Cycle length	Ovulation day for a 14-day luteal phase
26	Day 12
28	Day 14
30	Day 16
32	Day 18
35	Day 21

How to find your ovulation day

Use ovulation predictor kits, basal body temperature charts or cervical mucus. A temperature rise confirms ovulation after it happened.

What shortens the luteal phase

Stress, extreme exercise, low body weight, thyroid problems, perimenopause and PCOS can all affect it. This calculator is for education and is not medical advice. Your own doctor, midwife or pediatrician should guide decisions about your care.

Frequently asked questions

What is a normal luteal phase?

10 to 16 days, average 12 to 14.

What is a short luteal phase?

Under 10 days.

Can I lengthen it?

Treat underlying causes; supplements are not proven.

How do I calculate my luteal phase?

Cycle length minus ovulation day.

Does the luteal phase vary by cycle?

Yes, by a day or two.

What is the follicular phase?

The time from period to ovulation.

Sources

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Effortless Math Team

5 minutes ago