Enter your ovulation date and next period date to calculate your luteal phase length, fertile window, and whether your luteal phase falls in the normal, short, or long range.
This luteal phase calculator is separate from a BMI calculator. Looking for body mass index? Use the BMI Calculator for Women instead.
The day the egg was released.
First day of your following period.
Helps estimate ovulation if you only know your period date.
The luteal phase is the second half of your cycle — the stretch between ovulation and the start of your next period. For most women it lasts 11 to 17 days, with 12 to 14 days being the most common.
Unlike the follicular phase (which can vary widely), the luteal phase tends to stay fairly consistent for each woman. This stability is why clinicians can estimate ovulation by counting backward approximately 14 days from your expected period date.
Normal
11–17
days
Most common: 12–14 days
Short
<11
days
May affect implantation
Long
>17
days
Uncommon; worth checking
The luteal phase must be long enough for a fertilized egg to travel down the fallopian tube and implant into a sufficiently thick uterine lining. If the luteal phase is too short (under 10 days), the lining may break down before implantation can occur, leading to very early pregnancy loss or difficulty conceiving. Progesterone is the key hormone here — it maintains the lining. Low progesterone often correlates with a short luteal phase, which is why women tracking fertility often monitor both luteal length and progesterone levels.
The luteal phase begins the day after ovulation and ends the day before your next period starts. In a typical 28-day cycle, ovulation falls around day 14, so the luteal phase spans roughly day 15 through day 28. If your cycle is shorter or longer, the luteal phase still tends to last 12–14 days — it's usually the follicular phase (before ovulation) that shifts, not the luteal one.
Example: ovulation on March 14, next period on March 28 → luteal phase = 13 days (March 15–27).
The average luteal phase is 12 to 14 days, with a normal range of 11 to 17 days. Because it stays fairly stable cycle to cycle, doctors often estimate ovulation by subtracting 14 from the day your next period is due.
A luteal phase consistently under 10 days is called a short luteal phase or luteal phase defect. It may make conception harder because the uterine lining doesn't have enough time to develop for implantation. Possible causes include:
The luteal phase is when implantation must happen — usually 6 to 10 days after ovulation. Progesterone keeps the uterine lining thick and receptive to a fertilized egg. If pregnancy occurs, the corpus luteum continues producing progesterone until the placenta takes over around week 10. A healthy luteal phase length and adequate progesterone are therefore both important when trying to conceive. If you're tracking for pregnancy, pair this tool with our Pregnancy Due Date Calculator and Menstrual Cycle Calculator.
The luteal phase is a phase of your menstrual cycle. BMI (body mass index) measures body weight relative to height — a completely different metric. Use the right tool below:
A calculator is a starting point — your body is the source of truth. Reach out to your OB/GYN or a women's health specialist if you notice any of the following:
The luteal phase is the time from ovulation to the start of your next period. A healthy luteal phase is 11–17 days, with 12–14 days being most common. Under 11 days is considered a short luteal phase.
Enter your ovulation date and the start date of your next period. The calculator counts the full days between them — that's your luteal phase length.
If you don't know your exact ovulation date, you can estimate it by subtracting 14 from your average cycle length.
Check your BMI alongside your luteal phase for a fuller picture of your cycle health.
Find your average cycle length, next period, and fertile window.
Discover which menstrual phase you're in today and how to support it.
Log periods, symptoms, and moods over time for pattern insights.
Understand your hormone patterns and how they affect energy and mood.
This page is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of your physician or other qualified healthcare provider with any questions you may have regarding your menstrual cycle, fertility, or a medical condition.
Free printable planners and calculators built for women's wellness — no account needed.
Printable cycle calendar, ovulation and luteal phase log, and symptom tracker — spot short or long luteal phases at a glance.
All the tools and guides in this cluster, in one place.
Predict your next period, fertile window, and phases.
OpenFind your average cycle length.
OpenEstimate when your luteal phase starts.
Current pageTrack irregular cycles and spot patterns.
OpenStep-by-step guide to counting cycle days.
OpenWhat's normal for cycle length.
OpenTiming and signs of the luteal phase.
Open