§tools · open utility
due date
calculator.
a quiet, evidence-based estimate.
Most due-date calculators online ask for a date, then bury the answer in a pop-up. This one is open, instant, and based on Naegele's rule (the same formula your obstetrician uses). No signup, no email, no ads.
estimated due date
Saturday, February 27, 2027
how the formula works
Naegele's rule estimates the due date as 280 days (40 weeks) from the first day of your last menstrual period — or 266 days (38 weeks) from the date of conception. It assumes a regular 28-day cycle. If your cycle is longer or shorter your obstetrician may adjust the estimate after the first ultrasound.
This calculator is for general guidance only. It is not a replacement for medical assessment.