Health & Fitness Calculators
Pregnancy Calculator
Estimate how far along a pregnancy is, the current trimester, and the due date from the first day of the last menstrual period.
Quick guide
Enter the first day of your last menstrual period. The calculator estimates how many weeks and days along the pregnancy is, the current trimester, and the due date, counting a full-term pregnancy as about 280 days from that date.
Read the full explanationHow It Works
Pregnancy is conventionally dated from the first day of the last menstrual period (LMP), about two weeks before conception. A full-term pregnancy lasts about 280 days (40 weeks) from the LMP.
Formula Used
Due date = LMP + 280 days (Naegele’s rule); current week = days since LMP ÷ 7.
Example Calculation
If the last period began 10 weeks and 3 days ago, the pregnancy is in the first trimester with a due date about 30 weeks away.
Practical Use Cases
- Track pregnancy week by week.
- Estimate the due date for planning.
- Know which trimester you are in.