About BabyDateCalc

BabyDateCalc was created with a simple goal: to provide expecting parents with free, accurate, and easy-to-use pregnancy calculators. We believe that every parent deserves access to reliable pregnancy tools without having to navigate paywalls, create accounts, or worry about their data being collected and sold.

Our calculators are built using established medical formulas and guidelines, including Naegele's Rule for due date estimation and the Institute of Medicine (IOM) guidelines for pregnancy weight gain. While our tools are designed to be as accurate as possible, they are intended for informational purposes only and should never replace professional medical advice.

How Our Calculators Work

Our pregnancy calculators use well-established medical methods:

• Due Date Calculation: Based on Naegele's Rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is the same method used by most healthcare providers.
• Gestational Age: Calculated from the first day of your LMP, which is the standard medical convention. This means you are considered “2 weeks pregnant” at the time of conception.
• Weight Gain Recommendations: Based on the 2009 Institute of Medicine (IOM) guidelines, which provide recommended weight gain ranges based on pre-pregnancy BMI.
• Ovulation Estimation: Based on the luteal phase typically lasting 14 days, so ovulation is estimated at cycle length minus 14 days after LMP.