Pregnancy calculators
Pick the first day of your last period to see your due date and how far along you are. The pages below cover every week from 4 to 40 and each month of the year.
How it works
The due date is 280 days after the first day of the last period. Weeks along are the days since that first day divided by 7. If you know the conception date instead, use the conception date calculator, which adds 266 days.
Worked example
Say the first day of the last period is 12 January. Add 280 days to reach 19 October. Add 70 days to reach 23 March, which is the start of week 10. 70 divided by 7 is 10. This example uses a 365-day year.
Common questions
Which pregnancy calculator should I use?
Use the last period calculator if you know that date. Use the conception date calculator if you know when you conceived, for example after fertility treatment.
How many weeks is a full pregnancy?
A full pregnancy is counted as 40 weeks, which is 280 days from the last period. Birth from week 37 up to week 42 counts as term.
What do the trimesters cover?
The first trimester covers weeks 1 to 13. The second covers weeks 14 to 27. The third runs from week 28 to the birth.
Is the due date exact?
No. Only a small share of babies arrive on the due date. Treat it as the middle of a window.