Weeks to months
Pregnancy weeks to months calculator
Enter how many weeks and days pregnant you are to see which month and trimester that is.
Updated
In short
How many months pregnant am I at each week?
Doctors count pregnancy in weeks, but it's often described as nine months. Using the usual grouping, weeks 0 to 13 are months 1 to 3, the first trimester. Weeks 14 to 27 are months 4 to 6, the second trimester. Weeks 28 to 40 are months 7 to 9, the third trimester. Since months aren't equal lengths, any conversion is approximate.
Your estimate
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This is an estimate, not a diagnosis or birth control.
General information, not medical advice. Your doctor or midwife can tell you what your own results mean.
| Month | Weeks | Trimester |
|---|---|---|
| 1 | 0–4 | 1 |
| 2 | 5–8 | 1 |
| 3 | 9–13 | 1 |
| 4 | 14–17 | 2 |
| 5 | 18–22 | 2 |
| 6 | 23–27 | 2 |
| 7 | 28–31 | 3 |
| 8 | 32–35 | 3 |
| 9 | 36–40+ | 3 |
How it's calculated
- Uses completed weeks: 8 weeks 3 days counts as 8 weeks.
- Months 1 to 9 group the weeks as in the chart, so they line up with ACOG's trimesters.
- Calendar months = days since your last period ÷ 30.44 (the average month).
- Weeks are the medical standard. Use them when talking to your doctor or midwife.
Gyne learns your real cycle and adjusts these estimates as you log.
Frequently asked questions
Is pregnancy 9 months or 10 months?
Both are used. 40 weeks is a little over 9 calendar months. If you group weeks into blocks of 4, you get 10. Doctors avoid the question by counting in weeks.
How many weeks is 5 months pregnant?
About 18 to 22 weeks in the usual grouping.
When does the second trimester start?
At 14 weeks 0 days. The third trimester starts at 28 weeks 0 days.
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