5 calculators
Women's Health Calculators
Cycle and pregnancy maths is all counting — but counting from the right day, in the right direction, and everyone counts differently.
All Women's Health calculators
About these calculators
These five calculators work from the dates you already know. The period and ovulation tools look forward from your last period to predict upcoming cycles and your fertile window. The pregnancy and due date tools tell you how far along you are and when to expect delivery. The conception calculator runs the other way — backwards from a due date or ultrasound to the likely date of conception.
Cycle lengths vary between people and from month to month, so treat every date here as an estimate rather than a fixed appointment. For anything you are relying on medically, confirm it with a midwife or doctor.
Which calculator do you need?
| Your question | Use this |
|---|---|
| When is my next period due? | Period calculator |
| When am I most fertile? | Ovulation calculator |
| How many weeks pregnant am I? | Pregnancy calculator |
| When is my baby due, including after IVF? | Pregnancy due date calculator |
| When did I conceive? | Conception calculator |
The key numbers in one place
- Average cycle: 28 days, but anything from 21 to 35 days is normal for adults.
- Ovulation: about 14 days before your next period, not always on day 14.
- Fertile window: the 5 days before ovulation plus ovulation day.
- Pregnancy: 280 days (40 weeks) from the first day of your last period, or 266 days from conception.
All these tools give estimates based on averages. They are not a form of birth control, and they do not replace advice from a doctor or midwife.