DYU FERTILITY · PATIENT TOOLS
Ovulation calculator
Estimate your fertile window from the first day of your last period and your usual cycle length. For regular cycles of 21–35 days.
PLAN WITH AN ESTIMATE
Your result will appear here
Enter your details and select Calculate. Dates are estimates and should be interpreted alongside advice from your clinician.
How the estimate works
The calculator estimates your next period from your cycle length, then counts back 14 days to estimate ovulation. The fertile window covers the five days before that estimate and the estimated ovulation day. Actual timing varies, even with regular periods.
This tool cannot confirm ovulation and must not be used for contraception or to time fertility medicines. If your cycles are irregular, ask a clinician about an assessment.
ASRM: Optimizing natural fertility ↗