Ovulation calculator
Ovulation and fertile window calculator
Plan ahead
Ovulation & fertile window calculator
Estimate your most fertile days from your last period and usual cycle length.
The day bleeding started, not when it ended.
Days from one period to the next — most are 21–35.
Days from ovulation to your next period. Usually 12–14.
That date is in the future — please pick the start of a period that has already begun.
An estimate, not a diagnosis. These dates assume a regular cycle and a typical luteal phase, and predict the cycle following the date you enter. Ovulation timing varies between people and between cycles, so this tool should not be relied on to achieve or avoid pregnancy. If your cycles are irregular or you have questions about your fertility, please speak with your doctor or fertility specialist.
Calculate your fertile window
Use this calculator to improve the chances of becoming pregnant, timing intercourse around ovulation day. Having sex daily, or second daily, in the days leading up to ovulation increases the likelihood of sperm being present when the egg is released.
Use ovulation predictor kits
Ovulation predictor kits can be used to detect a surge in luteinizing hormone (LH), this signals peak fertility and is an especially good time to have sex. It is recommended to begin testing a few days before you expect ovulation. You can use this calculator to predict ovulation day. You need to adjust your average cycle length. Once the test is positive have sex that day and the next day.
What is ovulation?
Ovulation is when an ovary releases an egg, typically around the middle of the cycle, about day 14 in a 28 day cycle. This can vary as cycle lengths commonly range from 25 to 35 days.
Are there signs of ovulation?
You may notice physical signs as ovulation is approaching. Cervical mucous often becomes clear, slippery and stretchy in the days beforehand, which helps the sperm travel more easily.
How does pregnancy happen?
For pregnancy to occur, several conditions need to be in place, a healthy egg, healthy sperm, open fallopian tubes, and a normal uterus. Once the egg is released from the ovary, the tips of the fallopian tube, sweep the egg into the tube. Little fibres on the inside of the fallopian tube beat the egg towards the uterus. Meanwhile, sperm need to swim in sufficient numbers and quality towards the egg. Once sperm reach the egg, the first few sperm soften the outside of the egg, known as the zona pellucida, allowing a single sperm to enter the egg. This is the moment of fertilisation. The fertilised egg, now known as an embryo, travels to the uterus, where it implants in the lining of the uterus, known as the endometrium.