TempoLife › Features › Due date, ovulation and weight gain › ovulation
Ovulation calculator
Ovulation about 14 days before the next period — so cycle length minus 14 days after the period start — with the fertile window of the 5 days before ovulation through the day after (ACOG).
These are estimates for planning, built from published methods (Naegele, ACOG, IOM) — not antenatal care. Your clinician adjusts dates to your actual measurements and history; that personalised answer is the one that counts.
Your window
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The method
The luteal phase — the days between ovulation and the next period — is the stable part of the cycle at about 14 days. So ovulation ≈ cycle length − 14, counted from the period start. The fertile window adds the survival times: about 5 days for sperm, about 24 hours for the egg.
Source: ACOG — fertility awareness-based methods · checked 2026-09-03
Frequently asked questions
When do I ovulate?
On average, 14 days before the next period starts. For a 28-day cycle that is day 14; for a 33-day cycle, day 19. The calculator does that arithmetic for your cycle length.
What is the fertile window?
The days intercourse can lead to pregnancy: sperm survive up to about 5 days and the egg about 24 hours after ovulation, so roughly the 5 days before ovulation plus the day after — the framing ACOG uses.
Is calendar math enough to plan a pregnancy?
It is a starting point. Cycles vary, ovulation shifts, and the calendar estimate can be off by days either way. Ovulation tests and basal-temperature tracking narrow it; for conceiving and for avoiding pregnancy, talk to a clinician.
Track the cycle, see the pattern
TempoLife keeps the calendar, the symptoms and the habits together — the pattern a clinician can actually read.