MedDroidPregnancy due date calculator
Built by MedDroid · formulas from Naegele's rule
Free · no sign-up · runs in your browserEstimate your baby's due date from the first day of your last period (with your usual cycle length) or from a known conception date. You also see how many weeks pregnant you are today and your trimester.
Pregnancy due date calculator
Your numbers stay in your browser. Nothing you type here is sent or stored.
Your result
Enter your details and press Calculate to see your result here.
How it works
Naegele's rule: due date = first day of your last menstrual period (LMP) + 280 days (40 weeks).
It assumes a 28-day cycle. If your cycle is longer or shorter, the calculator adds (cycle length − 28) days. For a 32-day cycle that is +4 days.
From a known conception date: due date = conception date + 266 days (38 weeks).
Weeks pregnant are counted from the LMP (or from 14 days before conception), which is how doctors count. Trimesters: first up to 13 weeks 6 days, second 14 to 27 weeks 6 days, third from 28 weeks.
Related pages
Not a diagnosis. This tool gives a general estimate from a standard published formula. It is not a diagnosis and does not replace a check-up by a qualified doctor. If you feel very unwell, call your local emergency number (India: 108 or 112).
Frequently asked questions
How accurate is a due date calculator?
It gives an estimate. Most babies are born within about two weeks either side of the due date. An early ultrasound scan usually gives the most reliable date.
Why is pregnancy counted from my last period and not from conception?
Most people know the date of their last period but not the exact day they conceived. So doctors count from the first day of the last period, which is about two weeks before conception.
My cycles are irregular. Can I still use this?
You can, but the result is less reliable. Enter your usual cycle length if you know it, and ask your doctor about a dating scan.
What if my scan date and this date are different?
Follow the date your doctor gives you. The scan measures your baby directly, so it is usually more accurate than a date worked out from your period.