Toolstia / pregnancy due date calculator
Pregnancy due date calculator
Enter the first day of your last period and your usual cycle length to see an estimated due date, the end of each trimester and how far along you are today.
The due date is 280 days (40 weeks) after the first day of the last period, moved earlier or later if your cycle is shorter or longer than 28 days. It is an estimate: only a small share of babies, around 4 to 5%, arrive on the day. An early ultrasound gives a more accurate date than a last period, so follow your midwife or doctor’s dating.
How it works
- Enter the first day of your last period.
- Set your cycle length.
- Read the due date and key dates.
How it is calculated
The due date is 280 days after the first day of your last period, adjusted if your cycle is not 28 days.
Conception date
Ovulation is assumed 14 days before your next period, which gives an estimated conception date.
Trimesters
The first trimester ends at 13 weeks and 6 days, and the second at 27 weeks and 6 days.
An estimate only
Only a small share of babies arrive on the due date. A scan gives a more accurate date.
Questions
Is this medical advice?
No. Follow your midwife or doctor’s dating.
What if my cycle is irregular?
The estimate is less reliable. A scan is a better guide.
Is my date stored?
Everything is worked out in your browser, and nothing you type is sent anywhere.