What Is Due Date Calculator?
The Due Date Calculator applies Naegele's rule by adding 280 days to the first day of your last period, and shifts that date by the difference between your cycle and 28 days whenever a longer or shorter cycle is entered. It also reports an estimated conception date 14 days before that last period, how many weeks and days along you are today, and which trimester that places you in. The remaining days and weeks to the due date are listed with the method used.
Who Uses the Due Date Calculator?
Expectant parents use it for a first estimate and to see how the 280 day figure is actually derived. Students and developers use it to watch Naegele rule worked through on real inputs, and anyone who already has a date from a scan can compare the two figures side by side.
How to Use the Due Date Calculator
- Enter the first day of your last period in the date field, and add your cycle length in days if you know it, since that field is preset to 28.
- Press the calculate button to get the estimated due date shown both in numeric form and written out in full.
- Read off your gestational age in weeks and days, your trimester on the progress bar, the estimated conception date, and the days and weeks still remaining.
Why Choose Our Due Date Calculator?
- Shows the reasoning behind the headline date: 280 days from the last period, shifted by however much your cycle differs from 28 days
- Reports gestational age in weeks and days plus the trimester, placing you on a 0 to 42 week bar so progress is visible at a glance
- The cycle length field adjusts the estimate for longer or shorter cycles, which a flat 280 days would ignore
- States plainly that due dates are estimates and directs you to follow the date from your midwife, doctor or early scan instead
Try the Due Date Calculator above — it is free, fast, and works on any device. Bookmark this page to return whenever you need it.