How Ovulation & Fertility Calculator works
The fertile-window estimate uses cycle dates and an assumed ovulation pattern. Calendar calculations cannot confirm ovulation and may be less useful when cycles are irregular.
Calculate estimated ovulation dates, fertile windows, next expected periods, and potential pregnancy due dates.
Estimate peak fertile days, ovulation dates, next periods, and pregnancy due dates
Ovulation typically occurs 14 days before the start of your next period. Your fertile window includes the 5 days leading up to ovulation and ovulation day itself.
A client-side Ovulation and Fertility Calculator. Predict your peak fertile window, estimated ovulation days, upcoming period dates, and estimated pregnancy due dates based on your menstrual cycle length.
Select the first day of your last menstrual period (LMP).
Adjust your average menstrual cycle length in days (default is 28 days).
View your estimated ovulation day, peak fertile window, and next period date.
Review the projected 3-month fertility calendar.
Calculates estimated ovulation dates and 6-day fertile windows
Predicts next expected menstrual period dates
Estimates potential pregnancy due date if conception occurs during ovulation
Generates a 3-month projected fertility calendar
Browser-based privacy — zero health or period data stored or transmitted
The fertile-window estimate uses cycle dates and an assumed ovulation pattern. Calendar calculations cannot confirm ovulation and may be less useful when cycles are irregular.
Health calculations are estimates based on the information entered. They do not replace examination, testing or advice from a qualified healthcare professional. Results may be less representative for children, pregnancy, medical conditions or unusual circumstances unless the tool specifically states otherwise.
This tool is designed to perform its main calculation or transformation in your browser. Do not enter information that the tool does not need, and review the site's Privacy Policy for analytics, advertising and third-party services.
Answers about how the tool works, its limitations, and how your information is handled.
Ovulation typically occurs about 14 days before your next period begins. In a standard 28-day cycle, ovulation usually occurs around day 14.
Your fertile window includes the 5 days leading up to ovulation plus ovulation day itself, as sperm can live inside the female reproductive tract for up to 5 days.
This tool provides estimates based on your average cycle length. If your cycle varies significantly month to month, ovulation predictor kits (OPKs) or tracking basal body temperature may provide additional accuracy.
No. The result is an informational estimate based on the inputs supported by the calculator. It does not replace advice, diagnosis or treatment from a qualified healthcare professional.
This tool is designed to perform its main calculation or transformation in your browser. Do not enter information that the tool does not need, and review the site's Privacy Policy for analytics, advertising and third-party services.
Continue with related UtilsDesk tools for the same type of task. Each tool has its own instructions, examples, methodology notes, and limitations.