Child BMI percentiles: how to read them in minutes
1) Core idea
Child BMI is calculated like adults, but it’s interpreted with age‑ and sex‑specific percentiles (growth charts). The percentile—not the raw BMI—drives the category.
2) Flow you can trust
- Enter age (years+months), sex, height, and weight.
- We compute BMI and map it to the correct growth chart.
- See percentile, category, and a visual marker for context.
3) Sanity checks
- Healthy range: 5th to 85th percentile.
- Underweight: < 5th; Overweight: 85th–95th; Obese: ≥ 95th.
- Units: if switching, we convert exactly (1 in = 2.54 cm; 1 lb = 0.45359237 kg).
4) Shortcuts
- If the child is growing along the same percentile curve over time, that’s usually reassuring.
- Use the same method (CDC or WHO) consistently for comparisons.
- Re‑measure height/weight if results look unexpected.
5) Pitfalls
- Comparing raw BMI across ages/sexes—use percentiles instead.
- Assuming one snapshot defines health; trends over time matter.
- Over‑restricting diet: focus on habits, not crash diets.
6) Micro examples
- 10y 6m boy, 140 cm, 35 kg → BMI ~17.9 → around median percentile.
- Switch units: 55 lb → 24.95 kg (55 × 0.45359237); 60 in → 152.4 cm (60 × 2.54).
7) Mini‑FAQ
- Which chart should I use? CDC in the US for 2–20y is common; WHO is also available—pick one and be consistent.
- Does high BMI always mean unhealthy? No—muscular builds can read higher; discuss with a pediatrician.
- How often to check? Typically during routine visits; more often if tracking a change.
8) Action tip
Save the percentile and recheck in a few months using the same method. Focus on balanced meals, daily activity, sleep, and supportive routines.