Pregnancy Calculator
How far along are you? Find your week of pregnancy, trimester and due date from your last period, conception date, IVF transfer or an ultrasound.
How pregnancy weeks are counted
Pregnancy is dated from the first day of your last menstrual period (LMP), not from conception. That is why you are already “2 weeks pregnant” around the time you conceive, and why a full-term pregnancy is 40 weeks (280 days) long — about 38 weeks after conception.
Weeks are written as completed weeks plus days: 10w 3d means 10 full weeks and 3 days, so you are in your 11th week.
Five ways to calculate
- Last period — the standard method. If your cycle is longer or shorter than 28 days, the dates move by the difference.
- Conception date — gestational age is 2 weeks more than the time since conception.
- IVF transfer — a day-5 blastocyst transfer counts as 2 weeks 5 days pregnant on the transfer day; a day-3 embryo as 2 weeks 3 days.
- Ultrasound — enter the gestational age measured at the scan. An early scan (before about 14 weeks) is the most accurate way to date a pregnancy.
- Due date — if you already know it, see how far along you are today.
Trimesters
| Trimester | Weeks |
|---|---|
| First | 0 to 13 weeks 6 days |
| Second | 14 to 27 weeks 6 days |
| Third | 28 weeks to birth |
The timeline below the result shows the main milestones for your dates, such as the first-trimester screening, the anatomy scan and the start of full term at 39 weeks.
Frequently asked questions
How many weeks pregnant am I?
Count from the first day of your last period. The calculator shows the completed weeks and days, your trimester and your due date.
Why does pregnancy last 40 weeks if conception is 2 weeks later?
Because it is counted from the last period, about 2 weeks before ovulation. From conception, a pregnancy lasts about 38 weeks.
Which date is more accurate — last period or ultrasound?
An early ultrasound, especially in the first trimester. If the two differ by more than a few days, doctors usually go by the scan.