Your estimated arrival date

Due date calculator

Three ways to calculate: last period, conception date, or IVF transfer. Everything stays on your device.

Due date calculator

First day of your last period

Average cycle length

28 days

Your dates stay on this device

Your personalized result — due date, current week and baby size — will appear here after you calculate.

Based on ACOG & NHS guidelines

100% private — data stays local

Reviewed against the official NHS calculator

How we calculate your due date

For a last-period calculation we use Naegele's rule: 280 days from the first day of your last period, adjusted by the difference between your cycle length and 28 days. Conception date adds 266 days. For IVF, a day-5 blastocyst transfer adds 261 days and a day-3 embryo adds 263. This aligns with NHS and ACOG guidance; your care team may adjust dates after an ultrasound.