Sex and birthday
WHO tables are split by sex and exact age.
Convert height and weight into WHO percentiles and z-scores. The P3, P50 and P97 curves for the same sex and age are drawn with your child marked.
Open Child Growth Percentile →WHO tables are split by sex and exact age.
Use the most recent height and weight measured the same way.
One percentile is a hint; the trend across visits is the signal.
Use Manlin to reflect, plan and take your next step.

No. Anything between P3 and P97 is common; watch growth along the curve.
No. The WHO tables ship with the page and the maths runs locally.