Your next fertile window
Predictions assume regular cycles. Do not use this calculator as a method of contraception.
How the fertile window is worked out
The calculator estimates ovulation as 14 days before your next period, then marks the 5 days before ovulation, the ovulation day and the day after as fertile. It repeats this for each cycle and shows your expected period days too, so you can plan ahead.
Getting the most from the calendar
- Use the average of your last 3 to 6 cycles for the cycle length.
- Update the calendar each time a new period starts.
- Combine it with ovulation test kits or cervical mucus tracking for a more accurate picture.
When to see a doctor
See your doctor if you have been trying for 12 months without success (or 6 months if you are 35 or over), or sooner if your periods are irregular, very painful or absent.
Frequently asked questions
Which day am I most fertile?
The two days before ovulation and the day of ovulation give the highest chance of pregnancy.
Can I get pregnant outside the fertile window?
It is less likely but possible, especially if your cycle is irregular or you ovulate earlier or later than predicted.
Can I use this calendar as contraception?
No. Calendar predictions are not reliable enough to prevent pregnancy.
Is my information saved?
No. The calendar is made in your browser and nothing is stored.