Pregnancy Calculator - Track Your Pregnancy Journey

Pregnancy Calculator

Calculate Your Pregnancy Timeline

Your Pregnancy Timeline

Due Date: -

Current Gestational Age: -

Trimester: -

Conception Date: -

Key Milestones

Purpose of the Pregnancy Calculator

This pregnancy calculator helps expectant parents track their pregnancy journey by estimating key dates and milestones. The tool provides valuable information including:

  • Due Date Estimation: Calculates your estimated delivery date based on different methods
  • Gestational Age: Shows how far along you are in weeks and days
  • Trimester Information: Identifies which trimester you're currently in
  • Pregnancy Milestones: Highlights important developmental stages

The calculator uses medically accepted formulas to provide estimates that help with prenatal planning, medical appointments, and understanding fetal development timelines.

Real-World Examples

Example 1 - LMP Calculation: Sarah's last menstrual period began on January 1. The calculator estimates her due date as October 8 (40 weeks later) and shows she's currently in her second trimester with specific fetal development milestones.

Example 2 - Conception Date: A couple using fertility tracking knows conception occurred on February 14. The calculator estimates their due date as November 7 (38 weeks from conception) and provides week-by-week development information.

Example 3 - Ultrasound Adjustment: An ultrasound at 12 weeks 3 days suggests a due date different from the LMP calculation. The calculator reconciles these dates to provide the most accurate timeline based on ultrasound findings.

Formulas and Algorithms

Last Menstrual Period (LMP) Method

Due Date: LMP + 280 days (40 weeks)

Conception Date: Typically estimated as LMP + 14 days (for 28-day cycles)

Conception Date Method

Due Date: Conception date + 266 days (38 weeks)

Ultrasound Method

Due Date Adjustment: If ultrasound dating differs from LMP by more than:

  • 5 days before 9 weeks
  • 7 days from 9-16 weeks
  • 10 days from 16-22 weeks
  • 14 days after 22 weeks
The ultrasound dates take precedence.

Gestational Age Calculation

Current Age = (Today - LMP) in weeks and days

Trimester Determination

  • First trimester: Weeks 1-12
  • Second trimester: Weeks 13-27
  • Third trimester: Week 28 until birth

Privacy Note

This pregnancy calculator processes all data locally in your browser. No personal information is collected, stored, or transmitted to any servers. Your pregnancy dates and information never leave your device, ensuring complete privacy and security.

Frequently Asked Questions

How accurate is the due date calculation?

Only about 5% of women deliver on their exact due date. The calculator provides an estimate based on averages - most babies are born within two weeks before or after the estimated due date. Ultrasound dating in the first trimester is typically most accurate.

Why is pregnancy calculated from LMP rather than conception?

Medical professionals use LMP because it's typically more easily remembered than conception date. This creates a standard reference point even though conception usually occurs about 2 weeks after LMP in regular cycles.

What if my cycle isn't 28 days?

For irregular cycles, the conception date or ultrasound dating methods may be more accurate. You can adjust the LMP date forward or backward based on your typical cycle length (add or subtract days from 28).

How does IVF pregnancy dating work?

For IVF pregnancies, use the embryo transfer date as your conception date. Add 266 days (38 weeks) for blastocyst transfers or 263 days for day-3 embryo transfers to calculate due date.

Why does my ultrasound due date differ from my LMP date?

Variations in ovulation timing, embryo implantation, or fetal growth can cause discrepancies. Ultrasound measurements in the first trimester are generally considered more accurate for dating than LMP.

Can the due date change during pregnancy?

Due dates are most accurate when established early (first trimester). Later ultrasounds typically don't change the due date unless there's significant discrepancy from earlier measurements.

What's the difference between gestational age and fetal age?

Gestational age counts from LMP (about 2 weeks older than fetal age). Fetal age (conceptual age) counts from actual conception. Medical professionals use gestational age as the standard.

How soon can pregnancy be detected?

Home pregnancy tests can typically detect pregnancy about 12-14 days after conception. Blood tests may detect pregnancy slightly earlier. Ultrasounds become reliable around 5-6 weeks gestational age.