By Team Hypomnema · Updated October 19, 2026
Estimate ovulation and fertile windows, compare projected cycles and download a private calendar. Not contraception advice.
Use the calculator
Enter the first day of your last period and usual cycle length.
Adjust period duration, regularity and luteal-phase assumptions.
Review projected cycles and download a summary or estimated calendar.
Understand the limits
Calendar estimates cannot confirm ovulation or diagnose fertility. Irregular cycles reduce reliability. Do not use this tool to identify safe days or prevent pregnancy. Inputs stay in browser memory.
Keep your information private
Calculations run on your device. Inputs are not saved to browser storage or sent to a calculation server. Downloading explicitly creates a file on your device; calendar files can contain sensitive estimates. Choose where you store or import them.
Try the workflow
Keep your original documents and review the output. You can also browse all guides or contact Team Hypomnema.