This calculator uses Naegele rule to estimate how far along a pregnancy is and how many days remain until the estimated due date, based on the number of days since the last menstrual period.
Sample input: Days since last menstrual period: 140
Weeks pregnant: 20 (second trimester)
You are about 20 weeks and 0 days pregnant (second trimester) by Naegele's rule, with about 140 days (20 weeks) until your estimated due date. This is an estimate; confirm with your healthcare provider.
We use Naegele rule, the standard clinical method: the due date is 280 days (40 weeks) after the first day of the last menstrual period, assuming a regular 28-day cycle.
Only about 4 percent of births happen on the exact due date. An early ultrasound dating scan is more accurate than the last-period method, especially with irregular cycles. This tool is an estimate only; confirm with your healthcare provider.
The first trimester runs to about week 13, the second from weeks 14 to 27, and the third from week 28 to birth. The tool tells you which trimester your estimate falls in.
No. This is an educational estimate, not medical advice. Always confirm dating and any decisions with your doctor or midwife, who can account for your individual history and scan results.