How many weeks pregnant am I?
Enter the first day of your last period or your due date to see your weeks and days today.
Updated October 13, 2026 · sources checked October 13, 2026
In short
Pregnancy is counted in weeks and days from the first day of your last period, so at conception you are already about 2 weeks pregnant. If you know your due date, count back 280 days to find that starting day. The first trimester ends at 13 weeks and 6 days, the second at 27 weeks and 6 days.
Reading weeks and days
Notes and scan reports usually write pregnancy as weeks plus days: 12+3 means 12 weeks and 3 days. Week 12 starts at 12+0 and ends at 12+6. The calculator gives the same format, from the date you enter.
| Trimester | From | To |
|---|---|---|
| First | Conception (about 2+0) | 13+6 |
| Second | 14+0 | 27+6 |
| Third | 28+0 | Birth |
When your scan changes the count
Once you have had a dating scan, use the date it gave you: enter your new due date in the calculator. ACOG considers a first-trimester ultrasound the most accurate way to confirm how far along you are.
Plan the weeks ahead
- Your full pregnancy calendar, week by week, with the NHS appointment schedule.
- The due date calculator, with IVF and scan dating.
Questions parents ask
Why am I "2 weeks pregnant" at conception?
Because the count starts from the first day of your last period, about two weeks before ovulation in a 28-day cycle. It is a convention that lets everyone use the same calendar.
What does "12+3" mean on my notes?
It means 12 weeks and 3 days of pregnancy, counted from the first day of your last period or from your dating scan.
Sources
- ACOG Committee Opinion No. 700, Methods for Estimating the Due Date (2017) checked October 13, 2026
- NHS — Your antenatal appointments checked October 13, 2026
Mamavela explains; it does not replace your midwife, doctor or pediatrician, who know your situation. If something worries you, call them. In an emergency, call 911 (US), 999 (UK) or 112.