How to Use Our Due Date Calculator

2 min read

How to Use Our Due Date Calculator

Knowing your due date is the first step in preparing for your new arrival. Our Due Date Calculator estimates your baby's expected birth date using standard obstetric methods.

What to Enter

• Last Menstrual Period (LMP) -- The first day of your last period. This is the most common method used by healthcare providers.
• Or Conception Date -- If you know the approximate date of conception, the calculator can work from that instead.

How the Calculation Works

The standard method (Naegele's Rule) takes the first day of your last period, adds 7 days, and counts forward 9 months -- totaling approximately 280 days (40 weeks) from LMP.

If using a conception date, the calculator adds 266 days (38 weeks), since conception typically occurs about 2 weeks after the start of the last period.

What to Keep in Mind

Your due date is an estimate, not an appointment. Only about 5% of babies arrive on their exact due date. Most healthy pregnancies deliver between 38 and 42 weeks.

The calculator also shows:

• Current week of pregnancy -- How far along you are today
• Trimester milestones -- When each trimester begins and ends
• Key development dates -- When major milestones occur

Your healthcare provider may adjust your due date based on ultrasound measurements, especially in the first trimester.

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