Cycle & Fertility
Cycle and fertility estimates, computed from the dates you enter using the methods ACOG and the published cycle literature describe — including how much natural variation those methods carry. Nothing you type here leaves your browser: there is no account, and no cycle data is stored or transmitted.
Everything you type here is computed in your browser. Nothing you enter is stored on a server, sent anywhere, or shared — there is no account and no health data to leak.
Period calculator
A period calculator projects your next period dates from the first day of your last one and your average cycle length. It lists the next six cycles with the fertile window in each, and shows how wide the prediction really is: in 612,613 tracked cycles, only 13 percent were exactly 28 days long.
Ovulation calculator
This ovulation calculator counts back from your next expected period rather than forward from your last one, because the first half of the cycle is what varies. It dates estimated ovulation, ACOG's fertile window of five days before to one day after, and the six-day conception window Wilcox measured in 1995.
Conception date calculator
A conception date calculator subtracts 266 days from an estimated due date, or adds 14 days to the first day of a last period, following the convention ACOG publishes. It returns a conception window rather than a single day, because sperm survive for several days and ovulation timing varies between cycles.
Implantation calculator
An implantation calculator dates the window in which a pregnancy implants, from your estimated ovulation date. Wilcox and colleagues measured this directly in 1999: implantation happened 6 to 12 days after ovulation, and 84 percent of it on days 8, 9 or 10. This page carries no ads.
hCG doubling time calculator
This works out the doubling time between two hCG results and the percentage change between them, using the interval you enter. It shows the arithmetic and the slowest rise Barnhart and colleagues recorded in 2004 for a viable intrauterine pregnancy. It does not interpret your result. This page carries no ads.
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