Luteal Phase Calculator

Free Luteal Phase Calculator

Use this free luteal phase calculator to find out how long your luteal phase is, based on your ovulation date and the first day of your next period. Your luteal phase length can be a useful piece of information when trying to conceive or investigating fertility concerns.

The luteal phase is the second half of your menstrual cycle, running from ovulation until your next period begins. It is generally more consistent in length than the first half of the cycle, typically lasting 10 to 16 days. A consistently short luteal phase (under 10 days) may not give a fertilized egg enough time to implant, which is why it is sometimes discussed in the context of fertility.

How to Use the Luteal Phase Calculator

• Enter your ovulation date, tracked using an ovulation predictor kit, basal body temperature charting, or ultrasound.
• Enter the first day of your next period.
• Click Calculate Luteal Phase to see your luteal phase length and classification.

Features

• Calculates the exact number of days in your luteal phase.
• Classifies your result as short, normal, or long.
• Explains what a short or long luteal phase can mean.
• Mobile-friendly with print, share, copy, and download options.

Frequently Asked Questions

How is luteal phase length calculated?

It is the number of days between your ovulation date and the first day of your next period. This calculator simply subtracts the two dates you enter.

What is considered a normal luteal phase length?

Most sources consider 10 to 16 days to be within the typical range, with 12 to 14 days being most common. Consistency across cycles matters more than the exact number.

What does a short luteal phase mean?

A luteal phase under 10 days may not allow enough time for a fertilized egg to implant before the uterine lining sheds. If you notice this consistently while trying to conceive, it is worth discussing with your doctor.

Is this calculator free?

Yes, this luteal phase calculator is completely free to use with no sign-up required.

Related Calculators

Want to predict your ovulation date in the first place? Try our ovulation calculator. Want to track your whole cycle and forecast future periods? Use the menstrual cycle calculator. Curious about your average cycle length from past periods? Check the cycle length calculator. Wondering when implantation happens? Use the implantation calculator. Already expecting? Try our pregnancy due date calculator.