What this tool answers
This page begins with a last-period date and cycle assumptions, then estimates ovulation timing forward. It does not start with a due date or identify the day of an actual conception.
Formula
Estimated ovulation = last period + cycle length − luteal-phase length.
Worked example: A 31-day illustrative cycle
A last-period date of July 10, 2026, a 31-day cycle and a 14-day luteal phase give an estimated ovulation date of July 27, 2026. The retained tool’s approximate window runs July 22–28. Actual timing may differ.
Load these worked-example inputs
Limitations
Cycle timing is variable. This calculation is not contraception, diagnosis, confirmation of pregnancy or proof of a conception date. Discuss pregnancy dating with a qualified clinician.
Frequently asked questions
Which date starts this cycle-based estimate?
It starts from the entered first day of the last menstrual period.
Why does changing cycle length change the estimated window?
The model uses cycle length to estimate the next period and subtracts the stated luteal phase.
Can a predicted ovulation date confirm conception?
No. It is an estimate based on assumptions, not confirmation that conception occurred.