Health

Pregnancy Trimester Calculator

Enter your Last Menstrual Period (LMP) to see your current trimester, week of pregnancy, and due date.

First Day of Last Menstrual Period (LMP)

Estimated Due Date

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Method

How this calculator works

Due Date = LMP + 280 days

Select the first day of your Last Menstrual Period (LMP).
The calculator adds 280 days to find your estimated due date.
It also calculates your current week of pregnancy and tells you which trimester you are in.

Examples

Worked examples

Real numbers, end-to-end results.

LMP: Jan 1, 2026

Due Date: Oct 8, 2026

If today is April 1, you are in the 2nd Trimester (Week 13).

Use cases

When to use it

Track your pregnancy progress.
Know which trimester you are currently experiencing.

Disclaimer: This calculator provides estimates for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for decisions affecting your health. Results depend on the accuracy of inputs provided.

FAQ

Frequently asked questions

How long is a trimester?

A pregnancy is divided into three trimesters. The first trimester is from conception to 13 weeks, the second is 14 to 27 weeks, and the third is 28 weeks until birth.

How is the due date calculated?

The standard calculation (Naegele's rule) adds 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP).