Pregnancy lasts about 40 weeks from the last period — 9 calendar months and a week. Doctors count in weeks; the month chart is the common way of grouping them, so sources can differ by a week at the edges.
| Month | Weeks | Trimester |
|---|---|---|
| 1st month | weeks 1–4 | First |
| 2nd month | weeks 5–8 | First |
| 3rd month | weeks 9–13 | First |
| 4th month | weeks 14–17 | Second |
| 5th month ← you | weeks 18–22 | Second |
| 6th month | weeks 23–27 | Second |
| 7th month | weeks 28–31 | Third |
| 8th month | weeks 32–35 | Third |
| 9th month | weeks 36–40 | Third |
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Doctors count pregnancy in weeks, but most of us think in months. Enter the first day of your last period — or just the weeks from your scan — to see which month of pregnancy you are in, how many calendar months have passed and your trimester.
The chart groups the 40 weeks into 9 months: weeks 1–4 are the first month, 14–17 the fourth, 28–31 the seventh and 36–40 the ninth.
| Or Weeks Pregnant | 22 weeks |
| + days | 3 days |
| You are in your | 6th month of pregnancy |
| Weeks pregnant | 22 weeks 3 days (week 23) |
| Completed months | 5 months 5 days (5.2 calendar months) |
| Trimester | Second (weeks 14–27) |
| Weeks to go until 40 weeks | 17 weeks 4 days |
| Calculated | from the weeks you entered |
6th month of pregnancy.
Try this example →| First Day of Last Period | 1 Jun 2026 |
| You are in your | 5th month of pregnancy |
| Weeks pregnant | 20 weeks 0 days (week 21) |
| Completed months | 4 months 18 days (4.6 calendar months) |
| Trimester | Second (weeks 14–27) |
| Weeks to go until 40 weeks | 20 weeks 0 days |
| Calculated | from your last period (Mon, 1 Jun 2026) |
| Due date | Mon, 8 Mar 2027 |
5th month of pregnancy.
Try this example →The 5th month (weeks 18–22), about 4½ calendar months.
The 6th month covers weeks 23–27.
40 weeks is about 9¼ calendar months; counted in 4-week blocks it is 10 'lunar' months, which is why both numbers are used.