Pregnancy due date calculator●
Find your estimated due date, how far along you are and when each trimester starts.
Pick how you know the start, then enter the date. Nothing you enter leaves this page.
Your estimate
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The dates you enter are used only in this browser tab. Nothing is sent, saved or tracked.
How the due date is worked out
A full pregnancy is counted as 40 weeks, or 280 days, from the first day of the last period. From your last period the calculator adds 280 days, which is the same as adding one year, subtracting three months and adding seven days (Naegele's rule). If your cycle is longer or shorter than 28 days, the date moves by the difference, because ovulation moves with it. From a conception date it adds 266 days, since conception happens about two weeks after the period starts. For IVF it counts from the transfer date and takes off the age of the embryo, 3 or 5 days. Trimester 1 runs to week 13, trimester 2 from week 14 and trimester 3 from week 28. A scan in early pregnancy is usually a more accurate guide than any date you enter here, so treat the result as a starting point and follow your midwife or doctor.
Date calculator →Common questions
How is the due date calculated?
The calculator adds 280 days to the first day of your last period, adjusted if your cycle is not 28 days. From a conception date it adds 266 days.
How accurate is a due date?
It is an estimate. Only a small share of babies are born on the exact day, and most arrive within a few weeks either side. Your midwife or doctor may update the date after an ultrasound.
What if my cycle is not 28 days?
Enter your usual cycle length. A 32-day cycle moves the due date 4 days later, and a 24-day cycle moves it 4 days earlier.
How does the IVF option work?
It counts back from the transfer date by the age of the embryo, 3 or 5 days, to find the conception date, and then adds 266 days.
Is this medical advice?
No. It is a date calculator. Talk to your midwife or doctor about your pregnancy and your due date.
Is the date I enter stored?
No. It is used in your browser tab only and is never sent or saved.