Adjusts for your cycle
Uses Naegele's rule and shifts the due date for cycles longer or shorter than 28 days, rather than assuming an average.
Pregnancy Due Date Calculator
Your estimated due date, current week and trimester milestones.
- Input
- No upload needed — instant
- Privacy
- Nothing is uploaded
- Cost
- Free · no sign-up · no watermark
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Overview
About the Pregnancy Due Date Calculator
Estimate your pregnancy due date from the first day of your last period and cycle length, and see your current week, trimester milestones and conception estimate.
A due date is counted from the first day of your last menstrual period, not from conception, because that date is the one most people can recall. Enter it here and this calculator estimates your due date, tells you how far along you are, and lays out the trimester milestones.
Naegele's rule
due date = LMP + 280 days
adjustment = (cycle length − 28) daysThe standard rule adds 280 days (40 weeks). If your cycle is longer or shorter than 28 days, ovulation — and therefore the due date — shifts by the same difference, which this calculator applies.
What the dates mean
Pregnancy runs about 40 weeks: the first trimester to week 13, the second to week 27 and the third to birth. Only about 5% of babies arrive on the exact due date; anywhere from week 37 to 42 is considered full term.
Private and precise
This calculator produces estimates from published formulas and is not medical advice. For anything about your health, talk to a doctor or a registered dietitian.
Step by step
How to use the Pregnancy Due Date Calculator
Enter the first day of your last menstrual period.
Set your average cycle length if it is not 28 days.
Read your estimated due date, current week and the trimester milestones.
Why use it
Benefits and common use cases
What this tool is good for, and what it deliberately does not try to do.
Know where you are
Shows how many weeks and days pregnant you are now and which trimester you are in, counted to today.
Milestones at a glance
A table lists the start of each trimester and the due date, so you can plan appointments and time off.
Questions
Frequently asked questions
Short, honest answers about quality, limits and privacy.
How is a due date calculated?
By Naegele's rule: the first day of your last period plus 280 days (40 weeks). If your cycle is not 28 days, the estimate is adjusted by the difference, because ovulation shifts with cycle length.
How accurate is the due date?
It is an estimate. Only around 5% of babies are born on the exact due date, and a full-term birth can happen anywhere from 37 to 42 weeks. An ultrasound in the first trimester gives a more accurate date than period math.
Why count from my last period?
Because the exact date of conception is usually unknown, pregnancy is dated from the first day of the last menstrual period, which is about two weeks before ovulation. That is why 'week 1' is before you are actually pregnant.