Pregnancy Due Date Calculator

Calculate your baby's due date

Enter Your Last Menstrual Period

How It Works

The due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP).

  • Add 280 days (40 weeks) to your LMP.
  • Assumes a regular 28-day cycle.
  • Guidelines may vary for irregular cycles.
  • Early ultrasound can provide a more accurate due date.

Note

This calculator provides an estimate. Consult your doctor for a precise due date.

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Understanding Due Dates

What is a Due Date?

A due date is the estimated date when your baby is expected to be born, typically calculated as 280 days (40 weeks) from the first day of your last menstrual period. This calculation assumes a 28-day menstrual cycle with ovulation occurring on day 14.

How Accurate are Due Dates?

Due dates are estimates, and actual delivery times may vary. Research shows:

  • Only about 5% of babies are born on their actual due date.
  • Most babies are born within 2 weeks before or after the due date.
  • First-time mothers may deliver after their due date.
  • Subsequent pregnancies may be shorter.

Factors Affecting Due Dates

Several factors can influence when your baby is actually born:

  • Irregular menstrual cycles: May affect calculation accuracy
  • Conception timing: Ovulation may not occur on day 14
  • Multiple pregnancies: Twins or multiples typically arrive earlier
  • Previous birth history: Past delivery patterns may influence current pregnancy
  • Maternal age: Age may affect pregnancy duration

Frequently Asked Questions