Example 1
- Weight: 35 kg
- Height: 140 cm
- Age: 10 y · boy
BMI 17.9 · percentile ~70.6
Child BMI: 35 ÷ 1.40² ≈ 17.9; CDC percentile ≈ 70.6 (healthy weight).
BMI Calculator for Children
Enter weight, height, age, and sex. At 35 kg, 140 cm, age 10, boy, BMI is 17.9 and the CDC percentile is about 70.6. At 40 kg, 150 cm, age 12 — BMI 17.8 and about the 49.8th percentile. This is BMI-for-age, not adult WHO cutoffs. The result separates percentile, CDC category, z-score, the 5th–85th band, and BMI at the 50th and 95th LMS percentiles.
Result
Enter weight, height, age, and sex. The result will appear here.
The calculator computes Quetelet BMI and the CDC BMI-for-age percentile (LMS) for ages 2–20. It is not a printed clinic chart and does not replace medical advice. Adult cutoffs are on the adult BMI page. Daily calories for adults are on TDEE.
How the result is calculated
Mass35 kg
Height1.40 m
BMI17.9
Percentile70.6
Child BMI on this page starts with Quetelet’s formula: mass in kilograms divided by height in meters squared. At 35 kg and 140 cm, height is 1.40 m, and 35 ÷ 1.40² is about 17.9. At 40 kg and 150 cm, BMI is 17.8. At 30 kg and 130 cm it is also 17.8.
The percentile does not come from weight and height alone. After you enter age (2–20), optional months, and sex, the calculator reads LMS parameters from the CDC BMI-for-age table, computes a z-score, then the percentile. For a 10-year-old boy at BMI 17.9 the percentile is about 70.6 (healthy weight). For a 12-year-old boy at 40 kg and 150 cm it is about 49.8. For an 8-year-old girl at 30 kg and 130 cm it is about 80.4.
CDC categories on this page: below the 5th percentile underweight, 5th–85th healthy weight, 85th–95th overweight, 95th and above obesity. The approximate 5th–85th BMI band shows typical BMI values for that age and sex. IOM EER appears at ages 3–18 as approximate kcal per day.
Enter weight and height per the field labels, then age and sex, then Calculate. With US units, weight is in pounds and height in inches — the calculator converts them before BMI. A decimal in 35.5 works. Zero height does not produce a result.
This is a screening estimate aligned with public CDC LMS data. It does not replace a clinician’s growth chart or medical advice. Adult WHO cutoffs belong on the adult BMI page.
How to use
- Enter weight and height, for example 35 kg and 140 cm (or the US equivalents).
- Enter age in years (2–20) and optional months 0–11.
- Choose sex and — if you want EER — IOM activity.
- Click Calculate. At 35 kg, 140 cm, age 10, boy, BMI is 17.9 and the percentile is about 70.6.
- Adult cutoffs live on the adult BMI page. Here you keep BMI-for-age.
Formula
Model: Quetelet BMI + CDC BMI-for-age LMS (Cole; ages 2–20).
BMI = mass[kg] / (height[m])²
When L ≠ 0: z = ((BMI/M)L − 1) / (L · S); percentile = Φ(z) · 100.
Optional IOM EER (ages 3–18) with the selected PA coefficient.
Quetelet, LMS, and percentile
First BMI from mass and height. Then — at ages 2–20 — the CDC percentile. At 35 kg, 140 cm, age 10 (boy), BMI is 17.9 and the percentile is about 70.6.
- BMI
- Quetelet quotient. 35 kg and 140 cm give 17.9. That number alone is not a percentile.
- LMS
- L, M, and S parameters from the CDC table for age in months and sex. They produce the z-score and percentile.
- percentile
- Where this BMI sits among peers of the same sex and age. About 70.6 at the age-10 example means above roughly 70% of the CDC reference peers.
- EER
- Approximate kcal/day from IOM at ages 3–18. At age 10, 35 kg, 140 cm, PA 1.25 that is about 2243 kcal/day.
Examples
Three sets with age and sex so the CDC percentile appears. Weight and height units follow the header.
Example 2
- Weight: 40 kg
- Height: 150 cm
- Age: 12 y · boy
BMI 17.8 · percentile ~49.8
Near the middle of the chart for a 12-year-old boy.
Example 3
- Weight: 30 kg
- Height: 130 cm
- Age: 8 y · girl
BMI 17.8 · percentile ~80.4
Still in the healthy-weight band (< 85th).
Related calculators
Frequently asked questions
What is a BMI calculator for children?
It computes Quetelet BMI and — at ages 2–20 with sex — a CDC BMI-for-age percentile (LMS). At 35 kg, 140 cm, age 10, boy, BMI is 17.9 and the percentile is about 70.6. Not adult WHO cutoffs and not a clinic-only local chart.
How do you calculate child BMI percentile here?
Enter mass, height, age (years and months), and sex. BMI = kg ÷ m²; at 35 kg and 140 cm that is 17.9. The CDC percentile is added for ages 2–20. The result does not replace a clinic visit.
What is a normal BMI for children on this page?
Healthy weight here means the 5th to under the 85th CDC percentile. Below the 5th is underweight, 85th–95th overweight, 95th and up obesity. The sample 35 kg / 140 cm / age 10 (boy) at ~70.6th sits in healthy weight.
Is this a child and teen BMI calculator?
Yes for ages 2–20 on the CDC LMS path. Teens in that range get a percentile the same way. Outside 2–20 the page still shows BMI but not the CDC percentile band.
What is a child BMI percentile?
It shows where the result sits versus peers of the same sex and age on the CDC charts used in the model.
How is this different from adult BMI?
Adult categories use fixed WHO cutoffs (18.5, 25, 30). For children and teens the same BMI quotient is compared with peers of the same sex and age on a percentile chart. Adult WHO bands from the adult BMI page do not apply here.
Where does the CDC percentile come from?
From the LMS method (Cole) on CDC BMI-for-age data for ages 2 to 20. The calculator interpolates L, M, and S for age in months, computes a z-score, then the percentile from the normal distribution. Without age, or outside 2–20, only BMI is shown.
What percentile categories does this page use?
CDC convention: below the 5th percentile — underweight; 5th to less than 85th — healthy weight; 85th to less than 95th — overweight; 95th or higher — obesity. These are screening labels, not a clinical diagnosis.
Is this the same as a clinic growth chart?
No. This page uses the public CDC LMS table. A clinic may use the same CDC charts or other references. The result here helps you read BMI-for-age; it does not replace a visit or a printed chart.
When does the IOM EER estimate appear?
At ages 3 to 18 with the selected IOM activity level. It is an approximate kcal/day from IOM equations, not a meal plan. Outside that age range the EER row stays blank.
How do US header units work?
With US units, weight is in pounds and height is in inches. The calculator converts them to kilograms and meters before BMI and percentile. The 17.9 and 70.6 examples are computed from kilograms and centimeters.
Does a decimal in weight work?
Yes. A comma or period means the same thing. 35.5 kg and 35,5 kg are the same mass.
Does the result replace a doctor visit?
No. It is a screening estimate from a quotient and the CDC table. Growth tempo, illness, and clinical context belong with a clinician or pediatric dietitian, not the percentile number alone.
Why is sex required?
Percentile charts differ for boys and girls. Without sex there is no correct percentile.
Do months of age matter?
Yes. Child BMI is compared in narrow age bands. Years + months give a sharper chart point.
How is BMI itself counted?
The same as adults: mass / height² (kg/m²). The percentile is a separate age-chart layer.
Do US units change the formula?
Mass and height convert to kg and m before BMI. The percentile still uses the same chart.
What is IOM activity for?
At ages 3–18 it gives an approximate EER in kcal/day. Outside that range the EER row stays empty.
What does this calculator compute?
Quetelet BMI (weight ÷ height²) and — with age 2–20 and sex — the CDC BMI-for-age percentile from the LMS table, plus z-score and an approximate 5th–85th BMI band. At 35 kg, 140 cm, age 10, boy, BMI is 17.9 and the percentile is about 70.6.
Sources
Quetelet BMI and CDC BMI-for-age (LMS) are public models. Clinic charts may use the same CDC data or other references.
- CDC — BMI Calculator for Child and Teen
- CDC — Growth Charts
- CDC — Percentile data files
- Wikipedia — Body mass index
Page updated October 21, 2026.