Gestational Age Calculator by LMP – Track Your Pregnancy Week

Pregnant and wondering how far along you are?

This Gestational Age Calculator helps you find out your current pregnancy week based on your Last Menstrual Period (LMP) — the most common method used by doctors and gynecologists.

Gestational Age Calculator by LMP – Track Your Pregnancy Week
Gestational Age by LMP
Reviewed by Dr. Anjali Mehra, MD – Obstetrician & Gynecologist
Last reviewed: July 2025
Based on standard OB/GYN guidelines used globally.

How to Use the Gestational Age Calculator

  1. Enter the first day of your Last Menstrual Period (LMP)
  2. Click Calculate
  3. Instantly get your:
    • 📆 Gestational age (in weeks & days)
    • 🍼 Estimated due date (EDD)
    • 🧸 Which trimester you’re in

👉 No login or email required. 100% private and secure

What Is Gestational Age?

Gestational age is the number of weeks since the first day of your last menstrual period (LMP) — not the date of conception.

Doctors use it to:

  • ✅ Track pregnancy progress
  • 📅 Set accurate due dates
  • 🧪 Schedule ultrasounds and tests

Even though actual conception occurs about 2 weeks after LMP, gestational age includes that time for medical consistency.

Example Calculation

LMP Date: 1 March 2025
✅ Gestational Age: 18 weeks, 3 days
✅ Trimester: Second
✅ Estimated Due Date: 6 December 2025

What’s Considered a Full-Term Pregnancy?

  • Normal gestational length: 38 to 42 weeks
  • Due date is estimated at 40 weeks from LMP

📝 Some pregnancies go a little early or late — that’s totally normal.

Who Should Use This Tool?

  • 🤰 Expecting mothers
  • 🩺 OB/GYN clinics
  • 📱 Health & pregnancy apps
  • 💻 Antenatal class providers

Why LMP Is the Most Reliable Start Point

  • 📅 Most women can recall their LMP date
  • 🩻 Used before ultrasound confirmation
  • ⏳ Sets consistent tracking for all pregnancy stages

💡 If you know your EDD or conception date, use our Gestational Age by EDD Calculator (coming next).

Pregnancy & Baby

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FAQ

It uses clinical LMP-based calculations, the same method OB/GYNs use.

If you’re unsure, try to estimate as close as possible. The more accurate your LMP date, the more precise the gestational age. If needed, your doctor may confirm dates via an ultrasound.

No. Gestational age counts from the first day of your LMP, while fetal age begins at conception (usually about 2 weeks later).

It gives an estimated due date based on medical standards (40 weeks from LMP). However, only about 5% of babies are born exactly on their due date — it’s just a guide.

This calculator assumes a regular 28-day cycle. If your cycle is shorter or longer, or irregular, consult your OB/GYN for a more tailored estimate.

For IVF pregnancies, gestational age is typically calculated based on embryo transfer date. Use an IVF-specific calculator or follow your clinic’s advice.

The tool uses standard medical definitions:

  • First trimester: 0–13 weeks
  • Second trimester: 14–27 weeks
  • Third trimester: 28 weeks onward