Weeks to months of pregnancy: calculator and full table
Hi everyone ❤️. One of the questions you hear most often when you find out you are pregnant is the one in this title: “I am 12 weeks, how many months is that?”. It is completely normal to get confused, because pregnancy is officially measured in weeks and trimesters, while in everyday life everyone talks in months.
So you do not have to do the maths or search all over the place, here is a weeks to months calculator that tells you in a second which month you are in, together with a full table and the key ideas to understand it all. The most important thing to remember: the official way to follow your pregnancy is by weeks and trimesters, not by months, so the months equivalent is a practical guide, not an exact measure (months are not all the same length).
Which month am I: the calculator
With the calculator above you just enter how many weeks pregnant you are (and the extra days, if you remember them). It will tell you:
- Which month you are in (from 1 to 9), using the most common equivalent.
- Which trimester you are in.
- How many weeks are left until week 40 (full term).
And if you prefer, you have the full table at the end of the article to check it in a glance.
Weeks to months of pregnancy table
This is the most widely used approximate equivalent. Remember that months are not a medical standard: the official measurements are weeks and trimesters.
| Month of pregnancy | Weeks |
|---|---|
| Month 1 | Weeks 1 to 4 |
| Month 2 | Weeks 5 to 8 |
| Month 3 | Weeks 9 to 13 |
| Month 4 | Weeks 14 to 17 |
| Month 5 | Weeks 18 to 22 |
| Month 6 | Weeks 23 to 27 |
| Month 7 | Weeks 28 to 31 |
| Month 8 | Weeks 32 to 35 |
| Month 9 | Weeks 36 to 40 |
If you are weeks and days along (for example, 12 weeks and 4 days), use the month that matches your whole week: at 12 weeks you are 3 months until you reach week 14, when month 4 begins.
How many months is 40 weeks of pregnancy?
A full-term pregnancy lasts around 40 weeks, which roughly equals 9 months (although, because of lunar months of about 4 weeks each, many people also describe it as about 10 lunar months). The medical way of measuring it is by trimesters:
- First trimester: from week 1 to week 13 (months 1-3).
- Second trimester: from week 14 to week 27 (months 4, 5 and 6).
- Third trimester: from week 28 to week 40 and beyond (months 7, 8 and 9).
This trimester split is exactly what your midwife or doctor uses to follow the progress of your pregnancy.
Why does it differ depending on where I look?
It is normal for one table to tell you that 24 weeks is 6 months and another to say 5. The reason is that there is no official table: each source decides how to split the weeks between months, and because a calendar month lasts between 28 and 31 days, the conversion is never exact.
What is agreed across the whole medical community is counting by weeks and trimesters. That is why in this article (and across the whole site) the reliable reference is the weeks: from there you can orient yourself by months, but if you have a specific doubt about your pregnancy, your healthcare professional is always the one to answer it.
Useful links to follow your pregnancy week by week
Now that you know which month you are in, these guides will come in handy:
- Our online gestogram calculates your estimated due date and the baby’s growth each week.
- The pregnancy weeks calculator tells you exactly which week you are in based on your last period.
- If you are trying to get pregnant, the fertile days calculator helps you find your fertile window and ovulation day.
- You can follow your progress with the guides for week 1 and week 12, or the whole week by week hub.
Frequently asked questions
How many months am I if I am 12 weeks pregnant?
At 12 full weeks you are 3 months (the third month covers weeks 9 to 13). From week 14 you move into the fourth month.
How many months is 20 weeks of pregnancy?
20 weeks is 5 months (the fifth month goes from week 18 to week 22). You are also in your second trimester.
How many months is 30 weeks?
30 weeks is 7 months (the seventh month goes from week 28 to week 31), within the third trimester.
Is pregnancy 9 or 10 months?
By calendar months, a full-term pregnancy (around 40 weeks) roughly equals 9 months. Some ways of counting use “lunar months” of about 4 weeks, giving about 10, but what matters — and what medicine uses — is weeks and trimesters.
Why do different weeks-to-months tables not match?
Because there is no official table: months last different lengths (between 28 and 31 days) and each source splits the weeks its own way. The exact and universal measure is weeks, and months are only a guide from there. For any doubt, talk to your doctor or midwife.
Is the weeks-to-months calculator reliable?
It is an approximate equivalent based on the most common table (month 1: weeks 1-4, up to month 9: weeks 36-40). It is useful to get your bearings, but the correct way to measure your pregnancy is by weeks and trimesters, which is what healthcare professionals use.
I hope this helps clear up the pregnancy months question ❤️. If you want to look deeper into your specific week, check out the week-by-week guides; and if you have symptoms you want to review, you can take our online pregnancy test to get some orientation. And for a laugh, do not miss the finger pregnancy test game (it is just a game, not a real test).
Remember this content is for information only. If you are pregnant and have any doubts about your pregnancy, always talk to your doctor or midwife: they are the ones who can guide you best ❤️.
