Luteal Phase Length Calculator
The luteal phase is the stretch of your cycle from ovulation to the first day of your next period. Because it is relatively stable, measuring it helps you predict future periods and estimate ovulation timing. Enter your ovulation date (from an ovulation test, basal body temperature shift, or other method) and the first day of your next period to get the luteal phase length in days. This is an educational cycle-tracking estimate, not a diagnosis.
Luteal phase formula
Luteal phase length = (next period date - ovulation date) in days
The calculation is the whole-day difference between the two calendar dates. The next period date must be after the ovulation date. The band label is a simple descriptive guide only (under 10 days short, 10 to 11 days borderline, 12 to 14 days typical, over 14 days longer than typical) and is not a medical assessment.
Worked example
Ovulation on 14 June 2026, next period on 28 June 2026:
- Luteal phase length = 28 - 14 = 14 days.
- Band: typical (12 to 14 days).
Luteal phase: frequently asked questions
What is the luteal phase?
The luteal phase is the part of the menstrual cycle from ovulation to the first day of your next period. During it the ruptured follicle forms the corpus luteum, which produces progesterone. It is the more constant phase of the cycle, often described as around 12 to 14 days, though it varies between individuals.
How is luteal phase length calculated here?
It is the number of whole days from your ovulation date up to (but not including) the first day of your next period. If you ovulated on 14 June and your next period started on 28 June, the luteal phase is 14 days. You can identify ovulation from a positive ovulation test, a basal body temperature shift, or another tracking method.
What luteal phase length is considered typical?
Many references describe a luteal phase of roughly 12 to 14 days as typical. A short luteal phase (sometimes defined as under about 10 days) is referred to as a luteal phase defect by some clinicians. This tool reports your measured length and offers no diagnosis. Discuss any concerns with a healthcare provider.
Why track the luteal phase?
Because it is relatively stable, the luteal phase length helps predict future periods and pinpoint ovulation timing when trying to conceive. Knowing it lets you estimate ovulation in future cycles as next period minus luteal phase length.
Official sources
- Office on Women's Health, U.S. Department of Health and Human Services: Your menstrual cycle.
- U.S. National Library of Medicine, MedlinePlus: Ovulation.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.