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When Is Your Baby Due Calculator

Reviewed by Calculator Editorial Team

Pregnancy due dates are calculated based on the first day of your last menstrual period (LMP) or the date of your ultrasound. This calculator provides an estimated due date using standard gestational periods.

How to Use This Calculator

To calculate your estimated due date:

  1. Select whether you want to calculate based on your last menstrual period or an ultrasound date.
  2. Enter the relevant date (LMP or ultrasound date).
  3. Click "Calculate Due Date" to see your estimated due date.

The calculator will display your estimated due date, the gestational period in weeks, and a chart showing your pregnancy timeline.

How the Due Date Calculation Works

The standard gestational period is considered to be 40 weeks (280 days) from the first day of your last menstrual period (LMP).

Formula

Estimated Due Date = Last Menstrual Period + 280 days

For ultrasound dates, the calculation is based on the gestational age at the time of the scan plus the remaining weeks to reach 40 weeks.

This calculation provides an estimate. Actual due dates may vary by several days due to individual differences in pregnancy length.

Example Calculation

If your last menstrual period was on January 1, 2023:

  • Estimated Due Date: January 1, 2023 + 280 days = October 8, 2023
  • Gestational Period: 40 weeks

This example shows the standard calculation. Actual due dates may vary.

Frequently Asked Questions

How accurate is the due date calculator?
The calculator provides an estimate based on standard gestational periods. Actual due dates may vary by several days due to individual differences in pregnancy length.
Can I use an ultrasound date instead of my last menstrual period?
Yes, the calculator accepts both last menstrual period dates and ultrasound dates. For ultrasound dates, it calculates based on the gestational age at the time of the scan.
What if I don't remember my last menstrual period?
If you don't remember your last menstrual period, you can use an ultrasound date or consult with your healthcare provider for a more accurate estimate.