Pregnancy weeks to months converter
Convert how far along a pregnancy is between weeks, months and days, and see the trimester.
That is the 2nd trimester, with about 20 weeks to the due date.
What it means
How far along is that?
Counted from the first day of the last period, as doctors do. Months are average calendar months; some books count four-week months instead. For information only.
Every unit
That point in every count
Learn
Three things worth knowing
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Weeks ÷ 4.35
Weeks divided by 4.35 gives calendar months: 20 weeks ≈ 4.6 months, 30 weeks ≈ 6.9.
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Naegele’s rule
Franz Naegele’s 1812 rule dates birth at 280 days (40 weeks) after the last period; it is still the starting point for due dates.
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Nine months is forty weeks
40 weeks is 9.2 calendar months, so “nine months” is close but short.
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Background
About counting pregnancy
Doctors count pregnancy in weeks from the first day of the last period, about two weeks before conception; a full-term pregnancy is about 40 weeks. That is 9.2 calendar months, which is why weeks are used: months do not divide evenly.
The first trimester runs to the end of week 13, the second to the end of week 27, the third to birth.