TopToolsAiEstimate your baby's due date based on the first day of your last menstrual period — a quick way to get a rough timeline alongside your doctor's official estimate. If the first day of the last period was 1 January 2026, the estimated due date comes out to roughly 8 October 2026, using the standard 280-day pregnancy estimate counted from that date.
Last updated: 1 Sep 2026
How to use Pregnancy Due Date Calculator
- Enter the first day of your last menstrual period.
- Click "Calculate Due Date" for an estimated due date using the standard 40-week rule.
- This is an estimate only — always confirm with your doctor.
Frequently asked questions
How accurate is this estimate?
It gives a standard 40-week estimate from your last period, the same starting point many doctors use — but an ultrasound-based estimate from your doctor is more precise.
Does it work if my cycle isn't exactly 28 days?
The calculation assumes an average 28-day cycle. If yours varies a lot, mention that to your doctor for a more accurate date.
What if I know my conception date instead of my last period?
You can estimate a similar due date by adding about 38 weeks to the conception date instead of 40 weeks from the last period.
How often do babies arrive exactly on the due date?
Rarely, in fact — only a small percentage of babies are born on the exact estimated due date; most arrive within a couple of weeks before or after.
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