Period began 1 January 2026
Due date: 8 October 2026 (28-day cycle). With a 32-day cycle: 12 October 2026.
Pregnancy due date calculator
Naegele's rule: 280 days from the first day of the last period, shifted if your cycle is not 28 days. Only about 4% of babies arrive on the estimated date; most come within two weeks either side. A dating scan is more accurate. This is information, not medical advice.
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Estimated due date
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How your due date is worked out
Pregnancy is counted from the first day of your last period, not from conception, which is why it adds up to 40 weeks even though the baby has only been growing for about 38. Naegele's rule, in use for over two centuries, adds 280 days to that first day. A period starting on 1 January 2026 gives a due date of 8 October 2026.
If your cycle is longer or shorter than 28 days, ovulation falls later or earlier, so the date shifts by the difference. A 32-day cycle moves the due date four days later, to 12 October. If you know the day you conceived, add 266 days instead.
Think of the date as the middle of a range. Few babies arrive exactly on it, and a normal pregnancy runs from 37 to 42 weeks. Doctors confirm it with an ultrasound, ideally between 8 and 13 weeks, when the baby's length is a reliable clock.
The calculator also marks the usual checkpoints: an early scan around week 6, the dating and nuchal scan at 11 to 14 weeks, the anomaly scan at 18 to 22, and the glucose test at 24 to 28. Your own doctor's schedule is what counts. Take this as a planning aid, and talk to your doctor for anything about your health.
Sources
What this calculator does not account for
- Your health, scan results and your doctor's advice.
- Irregular cycles, which make the last-period method unreliable.
- Twins or complications, which change the schedule.
How this is calculated
Formula: Naegele's rule
due date =last period + 280 days + (cycle length − 28)What the symbols mean
- 280Forty weeks counted from the first day of the last period.
- cycleAverage days between periods. 28 is the textbook figure.
Good to know
- From conception, add 266 days. Ovulation is usually about 14 days after your period began.
- To count days between any two dates, use days between dates.
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Worked examples
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<iframe src="/embed/pregnancy-due-date" title="Due date" width="100%" height="720" style="border:0;max-width:42rem" loading="lazy"></iframe>Questions
How accurate is a due date?
Only about 4 to 5% of babies arrive on the estimated date. Most are born between 37 and 42 weeks.
Why does my scan date differ?
Scans measure the baby, not your cycle. If it differs by more than about a week early on, doctors usually go with the scan.
How are the trimesters divided?
First trimester up to 13 weeks and 6 days, second to 27 weeks and 6 days, third from 28 weeks until birth.
What if my cycle is irregular?
The last period method is unreliable then. Get an early ultrasound to confirm the date.