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Due Date Calculator

Real-time Engine

Estimate your due date and pregnancy timeline from the first day of your last menstrual period. Results are estimates and do not replace clinical dating.

Estimate your due date

Enter the first day, not the last day, of the period.
days
Editable from 20 to 44 days. Use 28 if that is your usual cycle.

Your dates are calculated in this browser and are not stored or sent to analytics.

Result

Enter the first day of your last menstrual period to see an estimated due date and pregnancy timeline.

Pregnancy Week CalculatorCalculate gestational weeks, days and trimester from LMP or an established due date.Conception Date CalculatorEstimate conception timing from an established due date or last menstrual period.
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How the estimated due date is calculated

A conventional estimated due date (EDD) is 280 days after the first day of the last menstrual period (LMP).

For supported cycle lengths, the estimate is adjusted by the difference from a 28-day cycle. This remains a simple calendar estimate and is not clinical dating for irregular cycles.

Limitations and when the estimate may differ

  • A due date is an estimate, not a guaranteed delivery date.
  • LMP dating assumes the entered period date is reliable. Ovulation timing and cycle regularity vary.
  • ACOG states that first-trimester ultrasound is the most accurate way to establish or confirm gestational age. Keep the EDD established by your maternity-care professional.

Important: This calculator provides general date estimates only. It does not diagnose pregnancy, assess fetal health or viability, or provide individualized medical advice.

Medical references

Medical methodology last reviewed:

Frequently Asked Questions

Why is pregnancy counted from the last period?

Gestational age is conventionally counted from the first day of the last menstrual period, about two weeks before conception in a standard 28-day-cycle approximation.

Can this replace my scan due date?

No. Use the due date established by your maternity-care professional for clinical decisions.

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