CALCULATOR · FREE免费 · Free
Pregnancy Weeks Calculator
Enter days since your last period to see pregnancy weeks, days left and trimester. This is an estimate, not medical advice.
--Weeks · weeks
--Days · days
--Trimester · trimester
--Days to 40 weeks · days
Estimates only; verify on site before ordering or building.
Example
| Item | Value | Unit |
|---|---|---|
| Days since LMP | 100 | days |
| Weeks | 14 | weeks |
| Days | 2 | days |
| Trimester | 2 | trimester |
| Days to 40 weeks | 180 | days |
Where people go wrong
- Counting from conception instead of the first day of the last period.
- Applying the 280-day rule when your cycle is not 28 days.
- Mixing ultrasound dating with LMP dating.
FAQ
When does pregnancy week one start?
From the first day of your last period, the clinical convention, not the actual conception date.
When does the second trimester start?
At 13 weeks; some sources say 12 or 14, so follow your clinician.