Your cycle at a glance
The green band is your fertile window. The pointer marks today.
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Pregnancy
Conception Calculator
Find your fertile window and the best days to try to conceive from your last period and cycle length, and see the due date if you conceive this cycle.
Best days to conceive
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Full fertile window—
Ovulation day—
Due date if you conceive—
How it works
Conception can only happen around ovulation, when an egg is available. Because sperm survive up to five days, the fertile window opens a few days before ovulation and closes about a day after. Timing intercourse in the two days before ovulation gives the highest chance of conceiving.
Ovulation = LMP + (cycle − 14)
Best days = ovulation − 2 … ovulation
Due date = ovulation + 266 days
Best days = ovulation − 2 … ovulation
Due date = ovulation + 266 days
Frequently asked questions
How often should we try during the fertile window?
Every one to two days across the window keeps sperm present when the egg is released, which maximises the odds without needing perfect timing.
Does a shorter or longer cycle change things?
Yes. Ovulation still tends to be about 14 days before your next period, so a longer cycle pushes the fertile window later, and a shorter cycle pulls it earlier.