Can I use a BMI calculator for a child under age 2?

No. All the tools in this group are designed for children aged 2 through 17 (or up to age 9 in some cases). BMI percentiles are not meaningful for children under 2, and pediatricians use different growth standards for infants.

Why do some calculators separate results for boys and girls?

Because boys and girls grow at different rates and have different body composition patterns during childhood and adolescence. The percentile rankings are sex-specific to give an accurate comparison to same-age, same-sex peers.

Is BMI the best way to tell if my child is a healthy weight?

BMI is a screening tool, not a diagnosis. It can indicate whether a child is underweight, healthy weight, overweight, or obese for their age and sex, but it does not measure body fat directly. A doctor or health visitor should always interpret the results alongside the child's overall health and growth pattern.

Do I need to know my child's exact date of birth to use these calculators?

Most calculators accept age in years and months, but the NHS tool specifically asks for date of birth to calculate the exact age in days. If you only know the approximate age, other tools will work with just years and months.

Can these calculators tell me if my child has a health problem?

No. These tools only provide a BMI percentile and weight category based on growth charts. They cannot diagnose medical conditions, and the results should be discussed with a pediatrician, school nurse, or GP for proper assessment and advice.

Body Metrics & Fitness6 options compared

BMI Calculator for Kids

This free NHS calculator checks BMI for children and teenagers aged 2 to 17, covering both girls and boys including age 9. It uses child-specific inputs such as date of birth, sex at birth, height, and weight to provide guidance. The page also explains who should use the tool and limitations of BMI interpretation.

BMI calculators

Editors’ Top PickBased on community votes

Inch Calculator

inchcalculator.com

This free Child & Teen BMI calculator takes age, gender, height, and weight to estimate BMI and percentile for childr...

Open Inch Calculator Read review →

Other OptionsRanked by votes

02
02
Omni Calculator
omnicalculator.com
The BMI calculator for kids helps you calculate BMI for both girls and boys up to and including nine years of age.
Open site View details
03
03
Calculator.net
calculator.net
This free BMI calculator accepts child ages (starting at age 2) and sex, so it works for young kids including boys an...
Open site View details
04
04
Centers for Disease Control and Prevention (CDC)
cdc.gov
This free Child and Teen BMI Calculator is designed for boys and girls ages 2 through 19, which includes children up ...
Open site View details
05
05
NHS
nhs.uk
This free NHS calculator checks BMI for children and teenagers aged 2 to 17, covering both girls and boys including a...
Open site View details
06
06
Cigna
cigna.com
This free interactive child BMI tool is intended for ages 2 through 19, including children up to age 9. It estimates ...
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Side by side

BMI Calculator for Kids options compared

Tool	Best for	Strengths	Limitations
Inch Calculator inchcalculator.com	Age 2-17 with CDC percentiles	CDC-based percentile classification Explanatory context for results	Ads on the page Fewer unit options
Omni Calculator omnicalculator.com	Boys and girls up to age 9	Separate calculations for boys and girls Age-appropriate percentile interpretations	Only covers up to age 9 No explicit age range beyond 9
Calculator.net calculator.net	Quick BMI and percentile lookup	Accepts child ages starting at age 2 Includes CDC percentile reference guidance	Basic interface with limited contextual guidance No age range beyond 9 specified
Centers for Disease Control and Prevention (CDC) cdc.gov	Official CDC growth chart standards	CDC growth chart standards Plots results on growth charts for interpretation over time	Government site may have less polished UX Primarily calculation-focused, less explanatory text
NHS nhs.uk	Full NHS guidance and age 2-17 range	Official NHS guidance Clear explanations of who should use the tool and limitations of BMI interpretation Covers age 9 and the full 2-to-17 range	Designed for users in the UK Requires date of birth input rather than just age
Cigna cigna.com	Percentile-style growth-chart context	Percentile-style growth-chart context for same-age, same-sex comparisons Publicly accessible without subscription	Cigna-branded site may prioritize insurance content Less focused on pediatric growth education

Buyer's guide

How to choose a bmi calculator for kids

When picking a BMI calculator for kids, the most important factor is whether the tool covers the child's full age range and explains how the results should be interpreted. Age range matters because BMI percentiles change with growth, and a tool that only goes up to age 9 will not work for older children. Look for calculators that use CDC or NHS growth chart standards and that provide clear context about what the percentile means, rather than just a raw BMI number. If you need separate boy/girl calculations or want the simplest input fields, that is a secondary consideration after age coverage and interpretive guidance.

Questions

BMI Calculator for Kids FAQ

Can I use a BMI calculator for a child under age 2?: No. All the tools in this group are designed for children aged 2 through 17 (or up to age 9 in some cases). BMI percentiles are not meaningful for children under 2, and pediatricians use different growth standards for infants.
Why do some calculators separate results for boys and girls?: Because boys and girls grow at different rates and have different body composition patterns during childhood and adolescence. The percentile rankings are sex-specific to give an accurate comparison to same-age, same-sex peers.
Is BMI the best way to tell if my child is a healthy weight?: BMI is a screening tool, not a diagnosis. It can indicate whether a child is underweight, healthy weight, overweight, or obese for their age and sex, but it does not measure body fat directly. A doctor or health visitor should always interpret the results alongside the child's overall health and growth pattern.
Do I need to know my child's exact date of birth to use these calculators?: Most calculators accept age in years and months, but the NHS tool specifically asks for date of birth to calculate the exact age in days. If you only know the approximate age, other tools will work with just years and months.
Can these calculators tell me if my child has a health problem?: No. These tools only provide a BMI percentile and weight category based on growth charts. They cannot diagnose medical conditions, and the results should be discussed with a pediatrician, school nurse, or GP for proper assessment and advice.

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BAI Calculator - Body Adiposity Index6 options

This free comparison calculator includes a full BAI computation component alongside BMI, using hip circumference and height inputs for BAI. It provides the BAI formula, output ranges, and context notes to help users understand the estimate. The tool is publicly accessible and usable without a required paid plan.