Pregnancy Due Date Calculator
Estimate your due date from the first day of your last period, with your likely ovulation window and trimester dates. A quick estimate — not medical advice.
The due date is counted as 280 days (40 weeks) from this date — the standard Naegele's rule estimate.
Ovulation is estimated at about 14 days after LMP for a 28-day cycle, adjusted for your cycle length.
Your estimated dates will appear here
Your estimated dates
This is an estimate only, not medical advice. Only about 1 in 20 babies arrive on their exact due date, and an ultrasound dating scan is more accurate. Always confirm dates with your doctor or midwife.
How to use
- Pick the first day of your last menstrual period, and enter your average cycle length.
- Click Calculate Due Date.
- Read your estimated due date, how far along you are, and your ovulation and trimester dates.
Frequently asked questions
How is the due date calculated?
By Naegele's rule: 280 days (40 weeks) counted from the first day of your last menstrual period. It assumes ovulation about 14 days after that date, adjusted for your cycle length.
How accurate is this due-date estimate?
It is an estimate. Only about 5% of babies are born on their exact due date, and most arrive within two weeks either side. An early ultrasound dating scan is more accurate than any LMP calculation.
What is the fertile window?
The days around ovulation when conception is most likely — about 5 days before ovulation through 1 day after. For a 28-day cycle that is roughly days 9 to 15 after the last period started.
Is this medical advice?
No. This calculator gives a general estimate for information only. Always confirm your dates and any health decisions with your doctor or midwife.
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