Pregnancy Due Date Calculator

STEP BY STEP

How to use pregnancy due date calculator

1. Enter the first day of your last menstrual period.
2. Set the usual cycle length and reference date.
3. Calculate the estimate and compare with your clinician’s dating.

WHEN IT HELPS

Common uses

• Estimate a due date from a known last menstrual period.
• Check estimated gestational weeks on a chosen date.

IN PRACTICE

Example

A last period starting 1 January 2026 and a 28-day cycle give an estimated due date of 8 October 2026.

GOOD TO KNOW

Can this confirm pregnancy or replace ultrasound dating?

No. This date-based estimate does not confirm pregnancy. A clinician and dating ultrasound can refine the due date, especially for irregular cycles.

Uses 280 days plus cycle length minus 28. Cycles must be 21–45 days for this estimate. Dates use whole calendar days. Irregular cycles reduce reliability; this is not a diagnostic tool.