Weeks to Months Converter
When Grandma asks 'how many months?', have an answer ready: approximately, and honestly.
“How many months is 22 weeks?”, fair question, and the honest answer is “approximately.” Enter your week and we’ll translate.
0–42 weeks.
Quick reference
| Weeks | You’re in your… | Trimester |
|---|---|---|
| 4 weeks | 1st month (0 completed) | 1st |
| 8 weeks | 2nd month (1 completed) | 1st |
| 12 weeks | 3rd month (2 completed) | 1st |
| 16 weeks | 4th month (3 completed) | 2nd |
| 20 weeks | 5th month (4 completed) | 2nd |
| 24 weeks | 6th month (5 completed) | 2nd |
| 28 weeks | 7th month (6 completed) | 3rd |
| 32 weeks | 8th month (7 completed) | 3rd |
| 36 weeks | 9th month (8 completed) | 3rd |
| 40 weeks | 9th month (9 completed) | 3rd |
How this works
We convert using the average calendar month (30.44 days): months completed = weeks × 7 ÷ 30.44, rounded down, capped at 9. There is no single official weeks-to-months mapping, which is why every answer is labeled approximate. Trimester boundaries follow ACOG definitions (second begins at 14w0d, third at 28w0d).
Sources & method
Due-date and gestational-age math follows ACOG Committee Opinion 700, “Methods for Estimating the Due Date” (Naegele’s rule and ART-based dating). Trimester boundaries follow ACOG patient-education definitions. All results are planning estimates, your prenatal healthcare provider determines your clinical due date.
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