Pregnancy Week Calculator

Find out how many weeks pregnant you are today, from your last period, your due date or your conception date.

This tool gives general estimates only and is not medical advice. Always follow the guidance of your healthcare provider.

How pregnancy weeks are counted

Pregnancy is measured from the first day of your last menstrual period, and a typical pregnancy lasts 40 weeks (280 days) from that date. "Weeks pregnant" means completed weeks, so someone who is 22 weeks and 3 days pregnant has finished 22 full weeks and is now in week 23.

You can start from whichever date you know:

Last period: the count starts on the first day of your last period, adjusted if your cycle is longer or shorter than 28 days.
Due date: the calculator counts back 280 days from your due date. Use this if your doctor or midwife has given you a due date, especially one from a scan, because the result will match theirs.
Conception date: conception happens about two weeks after the start of your last period, so the calculator adds 14 days.

Pregnancy weeks to months

Doctors and midwives count in weeks, but friends and family usually ask how many months along you are. Months are not exactly four weeks long, so charts differ slightly. This one keeps each trimester to three months:

Month	Weeks pregnant	Trimester
1	0–4	First
2	5–8	First
3	9–13	First
4	14–17	Second
5	18–22	Second
6	23–27	Second
7	28–31	Third
8	32–35	Third
9	36–40	Third

Gestational age and fetal age

The number this calculator gives is your gestational age, counted from your last period. It is the number your provider uses for appointments, scans and tests. Fetal age is counted from conception and is about two weeks less. So at 10 weeks pregnant, your baby has been developing for about 8 weeks.

Appointments by week

Timing varies between countries and providers, but these are common points in pregnancy care:

About 10 to 14 weeks: a dating scan, which can confirm or adjust your due date.
About 18 to 21 weeks: the mid-pregnancy anatomy scan.
16 to 24 weeks: when most people first feel their baby move. It is often later in a first pregnancy.
From 28 weeks: the third trimester, when check-ups usually become more frequent.

Frequently asked questions

Am I 6 weeks pregnant or in week 7?

Both. "6 weeks pregnant" means you have completed six full weeks, so you are now in your seventh week. Providers usually give completed weeks and days, such as 6 weeks and 3 days.

How many weeks is a full pregnancy?

About 40 weeks (280 days) from the first day of your last period, which is about 38 weeks from conception. Full term runs from 39 weeks to the end of 40 weeks.

How many months pregnant is 20 weeks?

About five months. 20 weeks is also the halfway point of a 40-week pregnancy.

Why is my doctor's number different from this one?

Your provider may have dated the pregnancy from an ultrasound, which can differ from the date based on your period. Choose "Due date" above and enter the due date they gave you to match their count.

I know when I conceived. Why am I two weeks further along?

Because pregnancy is counted from your last period, which starts about two weeks before conception. Those two weeks are included in every pregnancy count.