How far along are you?
This calculator tells you how many weeks and days pregnant you are today, which trimester and month you are in, how far you are toward your due date and how many days remain. Enter either the first day of your last period or your due date.
How pregnancy weeks are counted
Weeks are counted from the first day of the last menstrual period, not from conception, which usually happens about two weeks later. So at conception you are already considered 2 weeks pregnant, and a full-term pregnancy lasts about 40 weeks, or 280 days.
- Weeks pregnant = days since the last period ÷ 7 (completed weeks)
- Current week = completed weeks + 1
- From a due date: last period = due date − 280 days
Worked example
Your last period started 100 days ago.
- 100 ÷ 7 = 14 weeks and 2 days.
- You are 14 weeks 2 days pregnant, in your 15th week.
- That is the start of the second trimester and the fourth month.
- You have covered 36% of the pregnancy, with 180 days to go.
Trimesters and months
| Trimester | Weeks |
|---|---|
| First | 1 to 13 weeks 6 days |
| Second | 14 weeks 0 days to 27 weeks 6 days |
| Third | 28 weeks 0 days to birth |
| Month | Weeks |
|---|---|
| 1 | 1 to 4 |
| 2 | 5 to 8 |
| 3 | 9 to 13 |
| 4 | 14 to 17 |
| 5 | 18 to 22 |
| 6 | 23 to 27 |
| 7 | 28 to 31 |
| 8 | 32 to 35 |
| 9 | 36 to 40 |
Counting in months is approximate, since 40 weeks is a little more than 9 calendar months.
What happens when
- Weeks 4 to 6: a home test turns positive and the heart starts beating.
- Weeks 8 to 14: dating ultrasound and first-trimester screening.
- Weeks 18 to 22: anatomy scan; many people feel the first movements.
- Week 24 onward: the baby has a chance of survival with intensive care.
- Weeks 37 to 42: the usual window for birth.
A note on medical advice
This calculator gives estimates based on averages. It does not replace advice from your doctor, midwife or health care provider, who will date your pregnancy and follow it with exams and ultrasounds.