Enter the first day of your last period (or your conception date) and the estimated due date, current week of pregnancy, and trimester update as you change the fields. Everything is computed in your browser; nothing is uploaded.
Pregnancy Due Date Calculator Online
Enter the first day of your last period, or a known conception date, and the pregnancy due date calculator returns the estimated due date, how many weeks and days along you are today, and which trimester that falls in. Every figure updates as you change a field, so there is no button to press.
Key features
- Two methods to choose from: first day of last period (LMP) or conception date. Picking one from the Method dropdown relabels the date field to match.
- Average cycle length is adjustable from 20 to 45 days and defaults to 28, so a longer or shorter cycle shifts the estimate instead of being ignored.
- Gestational age is reported in completed weeks plus days, with the matching trimester beside it.
- Your dates stay in the browser - the due date is worked out on this device, with no upload and no account.
How the estimate is made
From a last-period date the calculator adds 280 days, adjusted up or down by the difference between your cycle length and a 28-day cycle. From a conception date it adds 266 days instead. That is the Naegele rule, the same arithmetic a paper pregnancy wheel uses. About 1 in 20 babies arrive on the exact estimated date, so read the result as a due window rather than an appointment.
Good to know
Results are general estimates and are not medical advice. An early dating ultrasound is more accurate than any date-based formula, so confirm your dates with your care provider.
Frequently Asked Questions
What does Pregnancy Due Date Calculator Online do?
It estimates a due date from either the first day of your last period or a known conception date, and reports how far along the pregnancy is today in completed weeks plus days, along with the matching trimester.
Which method should I pick, last period or conception date?
Use the first day of your last period (LMP) when you know that date - it is the usual starting point and lets you set your average cycle length. Pick the conception date method when you know roughly when conception happened, for example after tracking ovulation.
Why does the average cycle length field change the due date?
The last-period method adds 280 days to your date on a 28-day cycle. A longer cycle means ovulation happens later, so the estimate moves later by the same number of days; a shorter cycle moves it earlier. The field accepts 20 to 45 days and defaults to 28.
How accurate is the estimated due date?
It follows the Naegele rule, the same arithmetic as a paper pregnancy wheel, so treat it as a due window rather than a fixed appointment - about 1 in 20 babies arrive on the exact date. An early dating ultrasound is more accurate than any date-based formula. Results are general estimates and are not medical advice.
Are my dates uploaded anywhere?
No. The due date is worked out in your browser on this device, with no upload and no account.