Ovulation Date Calculator — Day-by-Day Cycle Chart
Find the day you are most likely to ovulate this cycle from your last or next period, with a day-by-day fertility chart for the whole cycle.
Estimate one cycle’s ovulation date from a last-period date or an expected next period. The chart shows what the calendar assumptions imply, not observations of ovarian activity. Dates can shift even in apparently regular cycles, so the page does not assign individual pregnancy probabilities to chart days.
How to use this tool
- Choose whether you know your last period or your next expected period.
- Pick that date.
- Enter your usual cycle length and, if you know it, your luteal phase length (14 days by default).
- Optionally set how long your period lasts so the chart marks those days.
Formula
Ovulation day = next period − luteal phase length
The next period is last period plus cycle length, when needed. This page defines luteal length as elapsed days from estimated ovulation to the next period. Thus cycle day = cycle length − luteal length + 1. The projected fertile interval is the six days ending at estimated ovulation. ASRM identifies the two days before actual ovulation as the period of highest fecundability.
Example
A period that started on 10 February 2026 with a 30-day cycle puts the next period on 12 March. Counting back 14 days gives ovulation on 26 February 2026, which is cycle day 17. The fertile days run from 21 to 26 February, with 24–25 February the peak.
Frequently asked questions
Is ovulation always on day 14?
No. Under this calculator’s explicit elapsed-day convention, a 28-day cycle and 14-day interval to the next period place ovulation on cycle day 15. Biological variation is much larger than this counting distinction, and calendar dates cannot establish the actual day.
Can I get pregnant the day after ovulation?
A calendar prediction cannot tell whether ovulation has already happened. The six-day interval describes timing relative to observed ovulation in research, not a guarantee that intercourse outside this projected interval cannot lead to pregnancy.
How do I find my luteal phase length?
Repeated cycle observations may help estimate it, but a first positive LH test is not the exact ovulation time and does not confirm ovulation. Keep the definition of elapsed days consistent and consult a clinician when interpretation matters.
Sources
This tool gives an estimate for general information only. It is not financial, tax, legal or medical advice — check with a qualified professional before you rely on the result.
Last updated: 2026-10-30