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How Many Weeks Pregnant Am I?

How far along you are today in weeks and days, the way clinics count it, with your trimester and how long until your due date.

v2026.10.13

Count from

days

From the first day of one period to the first day of the next. 28 if you’re not sure.

Your dates stay on this device: nothing is sent, saved or added to the address bar.

ExampleA last period 12 weeks 3 days ago

12 weeks 3 days

1st trimester, week 13 of pregnancy. 193 days until the due date, Sat, Apr 24, 2027.

12+3weeks of 40
  • Started Jul 18 (week 0)
  • Week 14 starts Oct 17
  • Term from Apr 3
Due date
Sat, Apr 24, 2027
Weeks to go
27 weeks 4 days

General information from published research, not a diagnosis or medical advice. Talk to a doctor before changing medication or treatment. Your clinician may set a different date after a scan; theirs is the one to plan with. Terms

Week by weekWeek 13 is Oct 10–16
WeekDatesTrimesterLabel
1Jul 18–241st
2Jul 25–311st
3Aug 1–71st
4Aug 8–141st
5Aug 15–211st
6Aug 22–281st
7Aug 29 – Sep 41st
8Sep 5–111st
9Sep 12–181st
10Sep 19–251st
11Sep 26 – Oct 21st
12Oct 3–91st
13nowOct 10–161st
14Oct 17–231st
15Oct 24–302nd
16Oct 31 – Nov 62nd
17Nov 7–132nd
18Nov 14–202nd
19Nov 21–272nd
20Nov 28 – Dec 42nd
21Dec 5–112nd
22Dec 12–182nd
23Dec 19–252nd
24Dec 26, 2026 – Jan 1, 20272nd
25Jan 2–82nd
26Jan 9–152nd
27Jan 16–222nd
28Jan 23–292nd
29Jan 30 – Feb 53rd
30Feb 6–123rd
31Feb 13–193rd
32Feb 20–263rd
33Feb 27 – Mar 53rd
34Mar 6–123rd
35Mar 13–193rd
36Mar 20–263rd
37Mar 27 – Apr 23rd
38Apr 3–93rdearly term
39Apr 10–163rdearly term
40Apr 17–233rdfull term
41Apr 24–303rdfull term
42May 1–73rdlate term

Week 1 starts on the first day of the last period. Trimesters from ACOG Committee Opinion 700; term labels from ACOG Committee Opinion 579.

How this works: Method, 7 sources, Checked against 2 worked examples,

How this works

Method

Clinics count a pregnancy from the first day of the last period, so the count starts about two weeks before conception. Weeks are whole weeks plus days: 12 weeks 3 days (often written 12+3) means 12 full weeks and three days into the thirteenth. Full method

Sources

How it’s tested

2 worked examples for this page are checked by automated tests before every release: given the inputs, the tool must show the expected answer.

Limits

General information from published research, not a diagnosis or medical advice. Talk to a doctor before changing medication or treatment. Your clinician may set a different date after a scan; theirs is the one to plan with.

Changes

  • First published: a due date from your last period, conception, IVF or a scan, with ovulation, conception, period and weeks-pregnant pages; nothing you enter leaves your device.

Every change on What’s new

How we make toolsReport a mistake

How the weeks are counted

Clinics count a pregnancy from the first day of the last period, so the count starts about two weeks before conception. Weeks are whole weeks plus days: 12 weeks 3 days (often written 12+3) means 12 full weeks and three days into the thirteenth.

With a due date, the calculator counts back 280 days to the start, then forward to today. For a due date of Monday, August 30, 2027, on Thursday, February 4, 2027 that is 10 weeks 3 days, in trimester 1.

A scan that measured 9 weeks 4 days on Monday, February 1, 2027 gives a due date of Thursday, September 2, 2027; enter that date here and the count follows the scan rather than your period.

weeks pregnant = (today − first day of last period) ÷ 7; with a due date, the start is the due date − 280 days

Week by week for a due date of August 30, 2027

Each pregnancy week’s dates, its trimester and, from 37 weeks, its term label.

Each pregnancy week’s dates, its trimester and, from 37 weeks, its term label.
WeekDatesTrimesterLabel
1Nov 23–291
2Nov 30 – Dec 61
3Dec 7–131
4Dec 14–201
5Dec 21–271
6Dec 28, 2026 – Jan 3, 20271
7Jan 4–101
8Jan 11–171
9Jan 18–241
10Jan 25–311
Show all 42 rows
11Feb 1–71
12Feb 8–141
13Feb 15–211
14Feb 22–281
15Mar 1–72
16Mar 8–142
17Mar 15–212
18Mar 22–282
19Mar 29 – Apr 42
20Apr 5–112
21Apr 12–182
22Apr 19–252
23Apr 26 – May 22
24May 3–92
25May 10–162
26May 17–232
27May 24–302
28May 31 – Jun 62
29Jun 7–133
30Jun 14–203
31Jun 21–273
32Jun 28 – Jul 43
33Jul 5–113
34Jul 12–183
35Jul 19–253
36Jul 26 – Aug 13
37Aug 2–83
38Aug 9–153early term
39Aug 16–223early term
40Aug 23–293full term
41Aug 30 – Sep 53full term
42Sep 6–123late term

Frequently Asked Questions

Why does my pregnancy count start before I conceived?

Because the first day of the last period is a date most people know, while the day of conception usually isn’t. Counting from it gives everyone the same starting line; it simply means the first two “weeks” come before the pregnancy began.

What does 12+3 mean?

Twelve completed weeks and three days, the same as “12 weeks 3 days”. It is in the thirteenth week of pregnancy, which is why some apps call it week 13.

How many weeks is each trimester?

In ACOG’s usage the first trimester is up to 13 weeks 6 days, the second 14 weeks 0 days to 27 weeks 6 days, and the third from 28 weeks to birth. Other sources draw the lines a week differently, so your clinic’s booklet may not match exactly.

Should I use my last period or my scan?

Your scan, if you have had one. Once a scan has confirmed or changed your due date, enter that due date here so the weeks match what your clinic says.