20 weeks pregnant
This calculator finds an estimated due date and how far along you are. The worked example is a pregnancy at exactly 20 weeks.
How it works
Due date equals the first day of your last period plus 280 days. Weeks along equals days since that first day divided by 7, rounded down. At 140 days along, 140 days remain.
Worked example
The first day is 5 August. Add 140 days to get 23 December. 140 divided by 7 is 20 weeks. Add the 140 days still to go and the total is 280. The due date is 12 May. The year in this example has 365 days.
Common questions
What if my cycle is not 28 days?
The 280 day rule assumes ovulation near day 14. If your cycle is much longer or shorter, your doctor may adjust the due date, often with an ultrasound. With a 35-day cycle some clinicians add 7 days, which would move 12 May to 19 May.
Does a leap year change the due date?
It can. A year with an extra day in February moves dates after that day by one. The calculator above uses the real calendar for your dates. If the span from 5 August includes a 29 February, 12 May reads one day earlier, as 11 May.
How many months is 20 weeks pregnant?
About 4.6 months. A pregnancy is 40 weeks, a little over 9 calendar months. Months are only a rough guide. At 20 weeks there are 140 days to the due date.
Which trimester is week 20?
Second trimester. The first trimester covers weeks 1 to 13, the second covers weeks 14 to 27 and the third runs from week 28 to the birth. Week 20 is week 7 of the second trimester.
Why do weeks start from the last period and not conception?
Most people know the date of their last period but not the day of conception. Counting from the last period gives everyone the same starting point. A pregnancy is about two weeks longer on paper than from conception. Counted from conception, this would be week 18, which is 126 days.