Estimate your due date from the first day of your last menstrual period using Naegele’s rule. Adjust for your average cycle length.
Naegele’s rule adds 280 days (40 weeks) to the first day of the last menstrual period. We also adjust for cycle lengths different from 28 days. The result is a useful estimate but ultrasound dating is more precise later in pregnancy.
A common method is Naegele’s rule: first day of the last menstrual period + 280 days (40 weeks). Ultrasound dating may refine this in clinical care.
It is an estimate. Only a minority of births occur on the exact due date. Your clinician may adjust dates based on ultrasound and history.
Irregular cycles make LMP-based dates less reliable. Early ultrasound is often used to improve dating accuracy.
No. This tool is educational only. Confirm dates and care plans with a qualified healthcare provider.