Free tool · Planning a pregnancy
Ovulation & period calculator.
Find your fertile days, your estimated ovulation date, when your next period is due and the earliest day to take a pregnancy test. It takes a few seconds, and nothing you enter is saved.
Always free
Fully private
Your cycle
Months ahead
How it works
Three dates, one calculation.
What is an ovulation calculator?
An ovulation calculator estimates when you release an egg each cycle, from the first day of your last period and your usual cycle length. It counts back about 14 days from your next expected period to find ovulation, and marks the five days before it as your fertile window.
01
Your next period
We add your cycle length to the first day of your last period. A 28-day cycle that began on 1 March points to the next period on 29 March.
02
Ovulation
Ovulation usually happens about 14 days before your next period, not on day 14 of every cycle. In a 32-day cycle, that is around day 18.
03
Your fertile window
Sperm can live for up to five days, so your fertile days are the five days before ovulation and ovulation day itself. The two or three days just before ovulation give the best chance.
Good to know
A guide, not a guarantee.
Cycles change from month to month. Stress, illness, travel, weight changes, breastfeeding and conditions such as PCOS can all move ovulation earlier or later, so treat the dates as a starting point. The more regular your cycle, the closer the estimate is likely to be.
Signs your body may be ovulating
- Clearer, slippery, stretchy vaginal discharge, a little like raw egg white
- A small rise in your resting body temperature that stays up after ovulation
- A mild ache on one side of the lower tummy for some women
- A positive ovulation (LH) test from a pharmacy kit
It isn’t a form of contraception
Counting days alone is not a reliable way to avoid pregnancy. If you don’t want to get pregnant, talk to your doctor about contraception that suits you.
When to talk to a doctor
- You have been trying for a baby for a year without success, or for six months if you are 35 or older
- Your cycles are usually shorter than 21 days or longer than 35 days
- Your periods are very painful, very heavy, irregular or have stopped
Questions
Frequently asked questions.
When am I most fertile?
In the five days before ovulation and on ovulation day itself. The chance of pregnancy is highest in the two or three days just before you ovulate.
Can I get pregnant just after my period?
It is possible, especially if your cycle is short. Sperm can survive for up to five days, so sex a few days after your period ends can lead to pregnancy if you ovulate early.
How accurate is an ovulation calculator?
It gives a good estimate if your cycles are regular. If they vary, ovulation tests or tracking your temperature and discharge will tell you more about your own pattern.
When should I take a pregnancy test?
Most home tests work from the first day of a missed period. If you don’t know when your period is due, wait at least 21 days after you last had unprotected sex.
What if my cycles are irregular?
Enter your average cycle length from the last few months, and use the dates as a rough guide. If your cycles are often shorter than 21 days or longer than 35, mention it to your doctor.
Is my information saved anywhere?
No. The calculator works entirely on your phone or computer. Nothing you type is stored or sent to us.
Read next
When you’re ready
Planning a pregnancy? We’re here.
From your first trimester to your first forty days after birth, our doctor-guided team cares for you at home.