4 weeks pregnant in months
A direct conversion using DueDateLab's transparent four-week pregnancy-month convention, with an average calendar-month comparison alongside.
DueDateLab — Weeks to Months · Week 4
Conversion
four-week pregnancy month
4 weeks = 1 four-week pregnancy month. That is about 0.9 average calendar months and 28 days since LMP.
Surrounding weeks
How this week sits in context, with two weeks on each side. The full chart from week 1 to week 42 is on the hub page.
| Week | Four-week pregnancy months | Calendar-month comparison | Days since LMP |
|---|---|---|---|
| 2 LMP-counted | 0.5 | ~0.5 | 14 |
| 3 LMP-counted | 0.75 | ~0.7 | 21 |
| 4 | 1 | ~0.9 | 28 |
| 5 | 1.25 | ~1.1 | 35 |
| 6 | 1.5 | ~1.4 | 42 |
Why "months" is approximate
Pregnancies are dated in weeks, counted from the first day of the last menstrual period. Months are a user-facing summary. There is no single clinical definition of a pregnancy month. DueDateLab uses a transparent four-week convention because it produces clean conversions: 1 month = 4 weeks = 28 days. The calendar-month comparison column uses an average calendar month of 30.4375 days (365.25 ÷ 12), so the same week comes out a little smaller in calendar months. Both numbers are correct; they describe the same span using different month definitions.
For a calendar date for the birth, use the Due Date Calculator. For the formula and the full week-by-week chart, see the methodology.