Pregnancy Due Date Calculator
Estimate a pregnancy due date from your last period or conception date.
What is the Pregnancy Due Date Calculator?
This tool estimates a pregnancy due date using two standard methods: Naegele's rule, which adds 280 days (40 weeks) to the first day of the last menstrual period and adjusts for cycle lengths other than 28 days, or a straightforward 266 days from a known conception date.
How to use it
- Choose whether you know the first day of your last period, or an exact conception date.
- Enter the date (and your average cycle length, for the LMP method).
- See the estimated due date, current week of pregnancy, and trimester.
An important accuracy note
Naegele's rule assumes a standard 28-day cycle with ovulation on day 14; this tool adjusts the estimate for a longer or shorter average cycle, but it's still a population-based estimate, not a measurement of your specific pregnancy. Only around 1 in 20 births happen exactly on the calculated due date — a full-term pregnancy is considered normal anywhere from 3 weeks before to 2 weeks after it. This tool is for general estimation only and does not replace dating confirmed by a clinical ultrasound or the guidance of a healthcare provider.
Want the "why" behind this tool? Read Why Due Date Calculators Assume a 28-Day Cycle.