Due date calculator
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.
Related reading
Implantation bleeding vs period: how to tell them apart
Implantation bleeding is light pink or brown spotting that can occur about 10–14 days after ovulation, when a fertilized egg attaches to the uterus. Compared with a period it is lighter, shorter (a few hours to 1–2 days), and arrives a little earlier — and it does not build into a full flow.
Read more →How soon can I take a pregnancy test?
For a reliable result, take a home pregnancy test from the first day of your missed period — about 14 days after ovulation. Some sensitive tests can detect pregnancy a few days earlier, but an early negative can still turn positive later.
Read more →Early pregnancy symptoms: the first signs
Early pregnancy signs — tender breasts, fatigue, nausea, frequent urination and mood changes — can appear around the time your period is due, sometimes a few days earlier. But they are non-specific and also happen before a period: only a pregnancy test confirms it.
Read more →Symptoms by DPO (7–14)
What each day past ovulation can feel like
Read more →References
- ACOG – Methods for Estimating the Due Date (Committee Opinion 700)
- NHS – Pregnancy due date calculator (nhs.uk)