HEALTH & EVERYDAY
Ovulation window calculator
Estimate ovulation day from cycle length.
Estimated result
Cycle day 14
- Estimated fertile window
- Days 9–15
Cycles vary and this must not be used as contraception.
SOURCES & REVIEW
Checked against official guidance
Last checked 14 July 2026 · Rule version GB-2026.27.1
NHS: Trying to get pregnant ↗COMMON QUESTIONS
Frequently asked questions
Is this an exact quote or tax return?
No. It is an estimate based on the inputs and assumptions shown.
When was this checked?
The method and linked official guidance were reviewed for the current UK release.