Pregnancy Due Date & Week Calculator
Estimate your due date, pregnancy week and trimester from the date or report you have.
Open calculator → Cycle planning
Period & Ovulation Calculator
One set of cycle dates, two questions. See when your next period is due, or when you are most likely to be fertile.
How to use it
- Enter the first day of bleeding of your most recent period — spotting the day before does not count.
- Set your average cycle length: the gap from the first day of one period to the first day of the next. If your cycles vary, use the length that happens most often and treat the result as approximate.
- Choose whether you want your next period dates or your fertile window. Both use the same two inputs, so you can switch between them without re-entering anything.
- For the fertile window, read the whole window rather than the single ovulation day. Sperm can survive up to five days, so the days before ovulation matter most.
What counts as a normal cycle — and what this cannot tell you
- A normal adult cycle is 21 to 35 days long, with 2 to 7 days of bleeding. In the first couple of years after periods start, and in the years approaching menopause, cycles are naturally more variable.
- Every date here assumes your next cycle is the same length as the one you entered. Travel, illness, thyroid problems, big changes in weight, stress and PCOS all shift the dates.
- The fertile window is calculated as the six days ending on the estimated ovulation day, which is the interval over which conception is realistically possible.
- This is not a method of contraception, and it cannot diagnose anything. A cycle consistently shorter than 21 days or longer than 35, or one that changes length markedly, is worth discussing with a gynaecologist.
When irregular periods need a gynaecologist
See a doctor if your cycles are consistently shorter than 21 days or longer than 35, if the length varies widely from month to month, if you bleed for more than 7 days or soak through protection hourly, if you bleed between periods or after sex, or if your periods stop for three months and you are not pregnant. These are common, treatable problems — irregular cycles are also the most frequent reason a fertile window estimate turns out to be wrong.
Clinical details & calculation method
- Next period start = last period start + cycle length, rolled forward until the date is in the future. Bleeding end = start + (bleeding days − 1).
- Ovulation is estimated as 14 days before the next expected period, i.e. last period + cycle length − 14.
- Fertile window = the six days ending on the estimated ovulation day (ovulation − 5 through ovulation, inclusive), following the ASRM description of the fertile interval.
- Earliest useful pregnancy test is taken as the day the next period is due; testing earlier raises the chance of a false negative.
- Supported inputs are 21–44 day cycles and 2–10 days of bleeding. Values outside the 21–35 day range are accepted and calculated, and flagged as worth discussing — they are not silently clamped, and the flag is not a diagnosis.
Frequently asked questions
Can I use this as contraception?
No. Ovulation can shift by several days from one month to the next even in women with regular cycles, and sperm can survive up to five days in the reproductive tract. Calendar methods have a high failure rate in ordinary use. Ask a doctor about reliable contraception.
Why is the fertile window six days and not more?
Because conception is realistically possible only in the five days before ovulation and on the day itself — that is the span over which sperm can still be present when the egg is released. The egg survives roughly 24 hours after ovulation.
My cycles are irregular. Is this any use?
Treat it as a rough guide only. With variable cycles the ovulation estimate can be days out, and each further projection drifts more. Ovulation tracking or a scan-based assessment is far more useful, and irregular cycles are themselves worth investigating.
When can I take a pregnancy test?
The date shown is the day your next period is due, which is the earliest a urine test is reliably useful. Testing before then increases the chance of a false negative. A blood beta-hCG test can detect a pregnancy a little earlier.
Does the bleeding-days field change my fertile window?
No. It is only used to estimate when bleeding will finish. Ovulation is worked out from your cycle length alone, which is why the field is optional for the fertile window view.
Emergency? Call Us
24x7 emergency and labour support in Amravati.