How many months pregnant am I?
Convert pregnancy weeks to months and days, or months to weeks. We use a transparent four-week pregnancy-month convention and show a calendar-month comparison alongside, so you can see why different sites give slightly different answers.
Pregnancy weeks to months chart
Lookup table from week 1 through week 42. The four-week pregnancy months column uses a clean 1 month = 4 weeks = 28 days convention. The calendar-month comparison column uses an average calendar month of 30.4375 days (365.25 ÷ 12) so the comparison is consistent across all rows.
| Week | Four-week pregnancy months | Calendar-month comparison | Days since LMP |
|---|---|---|---|
| 1 LMP-counted | 0.25 | ~0.2 | 7 |
| 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 |
| 7 | 1.75 | ~1.6 | 49 |
| 8 | 2 | ~1.8 | 56 |
| 9 | 2.25 | ~2.1 | 63 |
| 10 | 2.5 | ~2.3 | 70 |
| 11 | 2.75 | ~2.5 | 77 |
| 12 | 3 | ~2.8 | 84 |
| 13 | 3.25 | ~3.0 | 91 |
| 14 | 3.5 | ~3.2 | 98 |
| 15 | 3.75 | ~3.4 | 105 |
| 16 | 4 | ~3.7 | 112 |
| 17 | 4.25 | ~3.9 | 119 |
| 18 | 4.5 | ~4.1 | 126 |
| 19 | 4.75 | ~4.4 | 133 |
| 20 | 5 | ~4.6 | 140 |
| 21 | 5.25 | ~4.8 | 147 |
| 22 | 5.5 | ~5.1 | 154 |
| 23 | 5.75 | ~5.3 | 161 |
| 24 | 6 | ~5.5 | 168 |
| 25 | 6.25 | ~5.7 | 175 |
| 26 | 6.5 | ~6.0 | 182 |
| 27 | 6.75 | ~6.2 | 189 |
| 28 | 7 | ~6.4 | 196 |
| 29 | 7.25 | ~6.7 | 203 |
| 30 | 7.5 | ~6.9 | 210 |
| 31 | 7.75 | ~7.1 | 217 |
| 32 | 8 | ~7.4 | 224 |
| 33 | 8.25 | ~7.6 | 231 |
| 34 | 8.5 | ~7.8 | 238 |
| 35 | 8.75 | ~8.0 | 245 |
| 36 | 9 | ~8.3 | 252 |
| 37 | 9.25 | ~8.5 | 259 |
| 38 | 9.5 | ~8.7 | 266 |
| 39 | 9.75 | ~9.0 | 273 |
| 40 | 10 | ~9.2 | 280 |
| 41 | 10.25 | ~9.4 | 287 |
| 42 | 10.5 | ~9.7 | 294 |
Why do some sites say 9 months and others say 10? Pregnancy lasts roughly 40 weeks from LMP. Divided into four-week months, that is 10 months. Divided into average calendar months (30.4 days each), that is closer to 9.2 months. Both numbers describe the same pregnancy. See the methodology for the formulas.
How this works
Pregnancies are dated in weeks, counted from the first day of the last menstrual period (LMP). The full term is 40 weeks from LMP; pregnancies normally end between 37 and 42 weeks. Months are a user-facing summary, not a clinical measurement, and there is no single "pregnancy month" definition.
DueDateLab uses a four-week pregnancy-month convention because it produces clean, deterministic conversions: 4 weeks = 1 month, 28 weeks = 7 months, 40 weeks = 10 months. The calendar-month comparison column uses an average calendar month of 30.4375 days, so the same week comes out closer to 9.2 calendar months at term. Both numbers are correct; they describe the same span using different month definitions.
When to see a clinician
This tool is for orientation, not diagnosis. Confirm your dating with your OB or midwife. An early ultrasound is the most accurate way to date a pregnancy. If you are looking for a calendar date for the birth, use our Due Date Calculator.
Read more: First Trimester Week by Week and Due Date vs Conception Date.
Frequently asked questions
How many months am I at 28 weeks pregnant?
28 weeks equals 7 four-week pregnancy months, which is about 6.4 average calendar months. Both numbers describe the same span; the difference is whether you divide by 4 weeks or by an average calendar month of 30.4 days.
Is pregnancy 9 months or 10 months long?
A full-term pregnancy lasts about 40 weeks from LMP. Divided into four-week pregnancy months, that is 10 months. Divided into average calendar months, that is closer to 9.2 months. Both summaries are accurate; they reflect different month definitions, not different pregnancy lengths.
Why are weeks 1-3 included if I am not yet pregnant?
Pregnancy weeks are counted from the first day of your last menstrual period, which is before conception. Weeks 1 and 2 are counted before pregnancy has technically occurred, and conception typically happens around week 3. The convention is universal in clinical dating because LMP is easier to know than the exact day of conception.
What if I am 28 weeks and 3 days pregnant?
Enter the days alongside the weeks in the calculator. 28 weeks and 3 days is 199 days since LMP, which is about 7.1 four-week pregnancy months, written as 7 four-week months plus 3 days. The calendar-month comparison is about 6.5.
Can I convert months to weeks instead?
Yes. Switch the calculator to "Four-week pregnancy months" and enter the number. 7 four-week pregnancy months equals 28 weeks, or 196 days since LMP. The reverse conversion uses the same 1 month = 4 weeks rule.
Is the four-week pregnancy month a clinical standard?
No. Clinical care tracks pregnancy in weeks. The four-week month is a transparent arithmetic convention used to translate weeks into a month-shaped summary. Different sites use different conventions, which is why month-based numbers vary; weeks always agree.