Pregnancy Due Date Calculator
Estimate a due date from the last period, a conception date or an IVF transfer date.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
from the last period: first day + 280 days + (cycle length − 28) from conception: conception date + 266 days IVF, day 5 transfer: transfer date + 261 days IVF, day 3 transfer: transfer date + 263 days
This is Naegele’s rule, adjusted for cycle length. Pregnancy is counted from the first day of the last period, about two weeks before conception in a 28-day cycle.
What to watch out for
Choose a starting point and fill in the fields for it. If you have had a dating scan, use the date from the scan. After IVF, the date from the transfer is normally the one used.
Frequently Asked Questions
How is a due date worked out from the last period?
Add 280 days to the first day of the last period, then adjust for a cycle longer or shorter than 28 days. From 1 January 2027, a 28-day cycle gives 8 October 2027 and a 35-day cycle gives 15 October 2027.
How is it worked out from a conception date or IVF transfer?
Conception on 15 January 2027 plus 266 days gives 8 October 2027. A transfer on 10 February 2027 gives 29 October 2027 for a day 5 embryo (261 days) or 31 October 2027 for a day 3 embryo (263 days).
How exact is the due date?
It is an estimate. Only about 1 in 20 babies arrive on the due date. A dating scan gives the date to use. After IVF, the date from the transfer is normally the one used.
What if cycles are irregular?
A date worked out from the last period is unreliable when cycles are irregular. A dating scan gives the date to use.