Safe period calculator
The "safe period" is the part of your cycle when conception is less likely — but ovulation shifts, so it is NOT reliable contraception: with typical use, 12–24 women in 100 become pregnant within a year. Use this tool to understand your rhythm, not to prevent pregnancy.
⚠️ NOT a contraceptive method. Calendar-based "safe days" fail for 12–24 in 100 couples per year of typical use (WHO/ACOG). If you do not want to become pregnant, use reliable contraception.
🔒 Calculated locally — your dates never leave your device
The calendar marks the higher-risk fertile window (5 days before ovulation through 1 day after) and the relatively lower-risk days around it, based on your average cycle.
Why it fails: ovulation can move with stress or illness, sperm survive up to ~5 days, and many cycles are not perfectly regular. If avoiding pregnancy matters to you, choose a reliable method (condoms, pill, IUD) — talk to a doctor.
Frequently asked questions
How safe is the safe period really?
With perfect calculation the calendar method still fails about 5% per year; with typical real-world use, 12–24%. That is roughly 1 unplanned pregnancy per 4–8 couples per year — far below condoms, the pill or an IUD.
Which days are the "safe" ones?
Days outside the fertile window (5 days before ovulation to 1 day after) are relatively lower risk. But because ovulation shifts, no calendar day is truly guaranteed safe.
What if we had unprotected sex during the fertile window?
If you want to avoid pregnancy, ask a doctor or pharmacist about emergency contraception as soon as possible — it is a backup, not a routine method.
More free tools
Related reading
References
- WHO/JHU – Family Planning: A Global Handbook for Providers, ch. Fertility Awareness Methods
- ACOG – Fertility Awareness-Based Methods (effectiveness data)
- CDC – Contraception: typical-use failure rates
This page will be reviewed by a named OB-GYN before launch. Educational content — not medical advice.
Medical disclaimer: This tool and content are for educational purposes only and are not a substitute for professional medical advice. If something feels wrong, see a doctor.