Pregnancy Due Date Calculator
Enter the first day of your last period and your usual cycle length. You get an estimated due date, how many weeks pregnant you are and the dates of key milestones. This is not medical advice.
An estimate only and not medical advice. Your midwife will confirm your dates, usually at the dating scan, and may change them. Speak to your midwife or GP if you are unsure of your dates.
Worked examples
From the last period
Last period started 5 January 2027, 28 day cycle, checked on 30 March 2027
Estimated due date: Tuesday, 12 October 2027 Weeks pregnant on Tue 30 Mar: 12 weeks Trimester: First Milestone | Date Dating scan window opens (10 weeks) | Tuesday, 16 March 2027 Dating scan window closes (14 weeks) | Tuesday, 13 April 2027 Anomaly scan window opens (18 weeks) | Tuesday, 11 May 2027 Anomaly scan window closes (20 weeks and 6 days) | Monday, 31 May 2027 Full term from (37 weeks) | Tuesday, 21 September 2027 Due date (40 weeks) | Tuesday, 12 October 2027 42 weeks | Tuesday, 26 October 2027
The due date is 280 days after the first day of the last period.
From conception
Conception on 1 February 2027, checked on 1 April 2027
Estimated due date: Monday, 25 October 2027 Weeks pregnant on Thu 1 Apr: 10 weeks and 3 days Trimester: First Milestone | Date Dating scan window opens (10 weeks) | Monday, 29 March 2027 Dating scan window closes (14 weeks) | Monday, 26 April 2027 Anomaly scan window opens (18 weeks) | Monday, 24 May 2027 Anomaly scan window closes (20 weeks and 6 days) | Sunday, 13 June 2027 Full term from (37 weeks) | Monday, 4 October 2027 Due date (40 weeks) | Monday, 25 October 2027 42 weeks | Monday, 8 November 2027
Counting from conception adds 266 days.
About Pregnancy Due Date Calculator
This pregnancy due date calculator estimates when your baby is due. Enter the first day of your last period and your usual cycle length, or the date of conception. It follows the NHS method, which counts 40 weeks from the first day of your last period, and shows how many weeks pregnant you are on any date.
A table lists the usual dates for the dating scan and the anomaly scan, when full term starts and the date you reach 42 weeks. A due date is an estimate and only a small share of babies arrive on it. This is not medical advice, and your midwife will confirm your dates, usually at your dating scan.
How to use Pregnancy Due Date Calculator
- Choose last period or conception.
- Enter the date, and your usual cycle length if you used the last period.
- Optionally enter a different date to check the weeks pregnant on that day.
- Read your due date and the milestone dates.
Common uses
- Finding an estimated due date soon after a positive test
- Planning leave and appointments
- Working out how many weeks pregnant you are today
- Checking the dates of the scan windows
Frequently asked questions
How does the NHS work out the due date?
It counts from the first day of your last period and gives a date 40 weeks later. The NHS calculator lets you change the cycle length, because the standard calculation assumes a 28 day cycle.
What if my cycle is not 28 days?
The tool moves the date by the difference from 28 days, as ovulation happens later in a longer cycle and earlier in a shorter one.
How accurate is a due date?
Pregnancy normally lasts from 37 to 42 weeks, and only a small number of babies are born on the due date. A scan at around 12 weeks gives a more accurate estimate.
Is this medical advice?
No. Speak to your midwife or GP about your dates and your care.