Due date calculator
Your estimated due date is about 280 days (40 weeks) after the first day of your last period, adjusted for your cycle length. Enter your dates below to see your due date and how many weeks pregnant you are.
Only your doctor can confirm gestational age and due date — especially after an ultrasound. This estimate is for orientation.
🔒 Calculated locally — your dates never leave your device
This calculator uses Naegele’s rule (last period + 280 days) with an adjustment when your cycle is longer or shorter than 28 days. Only about 1 in 20 babies arrives exactly on the due date — most are born within two weeks either side.
Your doctor may adjust the date after a first-trimester ultrasound, which is the most accurate dating method.
Frequently asked questions
How is the due date calculated?
By Naegele’s rule: first day of your last period + 280 days, adjusted by (your cycle length − 28). An early ultrasound may refine it.
How many weeks pregnant am I?
Pregnancy weeks count from the first day of your last period — not from conception. The calculator shows your current week and trimester automatically.
Is the due date exact?
No. It is the middle of a range: most babies are born between 38 and 42 weeks. Treat it as a planning anchor, not a deadline.
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Related reading
References
- ACOG – Methods for Estimating the Due Date (Committee Opinion 700)
- NHS – Pregnancy due date calculator (nhs.uk)
This page will be reviewed by a named OB-GYN before launch. Educational content — not medical advice.
Medical disclaimer: This tool and content are for educational purposes only and are not a substitute for professional medical advice. If something feels wrong, see a doctor.