Baby percentile calculator
Enter one measurement and get the percentile — called the centile in the UK, Ireland and Australia. The number is calculated from the official WHO Child Growth Standards, the same tables your paediatrician or health visitor plots against. Nothing is uploaded: the maths runs in your browser.
This tool does not give a diagnosis and does not replace a check-up. A single measurement means little: what matters is whether your baby follows their own curve over time. If the curve crosses two printed lines downward, show it to your doctor.
Keep the whole curve, not one number
Sunny Seed stores every measurement, draws the curve and calculates centiles on your phone — offline, with nothing sent anywhere.