Naegele Due Date Calculator
Estimate pregnancy due date from the first day of the last menstrual period using Naegele's rule.
How to Use the Naegele Due Date Calculator
- Enter the first day of your last menstrual period in YYYY-MM-DD format.
- Click Calculate to see estimated due date and current gestational age.
Use Cases
- •First-trimester pregnancy planning.
- •Scheduling antenatal appointments.
- •Estimating gestational age for prescribing decisions.
Formula
Due date ≈ LMP + 280 days (40 weeks). Naegele's rule assumes a regular 28-day cycle with ovulation on day 14.
Frequently Asked Questions
How accurate is Naegele's rule?
Naegele's rule gives an estimate accurate to within about ± 1 week for most pregnancies with a regular 28-day cycle. Ultrasound dating in the first trimester is more accurate.
What if my cycle is not 28 days?
If your cycle is longer, shift the due date forward by the number of days your cycle exceeds 28 (for example, 35-day cycle → add 7 days). Shorter cycles subtract.
Disclaimer
Educational use only. Always confirm dating with your healthcare provider.