Enter your baby's birth date to see all Wonder Weeks (development leaps) with descriptions and timing.

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About the Wonder Weeks Calculator

The **Wonder Weeks Calculator** helps parents predict and understand their baby’s developmental leaps — key stages when a child’s brain goes through rapid growth. During these leaps, babies often learn new skills, but they may also become fussier, clingier, or experience changes in sleep and feeding.

How the Wonder Weeks Calculator Works

• Enter your baby’s birth date or due date for the most accurate results.
• Instantly see a personalized schedule of Wonder Weeks from birth up to 20 months.
• Each leap comes with a short description of what’s happening and practical tips on what parents can expect.

Why Wonder Weeks Matter

Wonder Weeks are based on the research of Dr. Hetty van de Rijt and Dr. Frans Plooij, who discovered predictable stages in baby brain development. These leaps often explain sudden changes in mood or sleep. While every child is unique, knowing the approximate timing helps parents prepare and support their baby through each phase.

Key Benefits of Using This Calculator

• Track your baby’s growth and mental development in a clear timeline.
• Anticipate when your child may need extra comfort and patience.
• Gain confidence as a parent by understanding that fussiness often links to progress.
• Use the chart as a guide, not a strict schedule — every baby develops at their own pace.

Note: Wonder Weeks are a helpful reference, but not all babies experience them at exactly the same time. Always use your baby’s unique behavior as the best guide.