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BMI Calculator

Use this BMI calculator to estimate body mass index, BMI category, and a healthy BMI weight range from pounds and feet/inches or kilograms and centimeters.

Method and assumptions documentedPlanning estimateSource note includedNo expert review claimed

Live calculator

BMI calculator

BMI25.8

Category: Overweight. BMI is a screening number, not a diagnosis.

Healthy BMI range129 - 174 lb

Approximate weight range for BMI 18.5 to 24.9 at this height.

Height70 inches

70 in / 177.8 cm used with weight to calculate BMI.

Use BMI as a screening estimate only. Body composition, age, pregnancy, athletic build, medical history, and clinician guidance can change the right interpretation.

Quick answer

BMI Calculator: what it calculates

BMI Calculator calculates BMI from pounds or kilograms, height, and unit system. The visible formula is BMI = kg / meters^2; US equivalent = pounds / inches^2 x 703.

ResultBMI
InputsPounds or kilograms, Height, Unit system
FormulaBMI formula

Formula

BMI formula

BMI = kg / meters^2; US equivalent = pounds / inches^2 x 703

BMI is a screening measure and does not directly measure body fat or health. The calculator supports US and metric inputs.

How to use

Steps

  1. Choose pounds or kilograms.
  2. Enter weight and height in the selected unit system.
  3. Read the BMI number and category.
  4. Use the healthy range as a broad reference, not a medical diagnosis.

Example

Sample calculation

Weight180 lb / 81.6 kg
Height5 ft 10 in / 177.8 cm
BMI25.8

Calculator use

Best for

  • Estimating adult body mass index from height and weight.
  • Checking the CDC adult BMI category and broad healthy-weight reference range.
  • Using BMI as one screening number before considering body composition, age, pregnancy, athletic context, or medical history.
  • Preparing a simple reference point for a clinician conversation, not a diagnosis.

Before relying on it

Check first

  • Treating BMI as a direct body-fat measurement or a full health assessment.
  • Applying adult BMI categories to children or teens, who use age and sex percentiles.
  • Ignoring muscle mass, pregnancy, older age, medical conditions, or other context that can make BMI misleading.
  • Changing diet, medication, or training based on BMI alone without appropriate professional context.

Details

What to know before using the result

Adult scopeAdults 20 and older

Adult BMI categories are different from child and teen BMI interpretation, which uses age and sex percentiles.

Screening useNot a diagnosis

BMI is one health indicator. It does not directly measure body fat, fitness, medical history, lab markers, or health risk by itself.

Category limitsBody composition matters

BMI can be misleading for muscular people, older adults, pregnancy, and some medical situations.

Source notes

References used for this calculator

Centers for Disease Control and PreventionProvides adult BMI categories and notes that BMI is a screening measure, not a substitute for medical advice.NISTProvides common U.S. customary to metric conversion references for length and mass.

Benchmarks

How to read the result

Under 18.5: Underweight.

A low BMI can be worth discussing with a qualified professional.

18.5 - 24.9: Healthy range.

Often used as the general adult BMI reference range.

25+: Above range.

BMI does not account for muscle mass, body composition, age, or pregnancy.

Calculator accuracy

Methodology and assumptions

Formula

BMI = kg / meters^2; US equivalent = pounds / inches^2 x 703

Inputs used

Pounds or kilograms, Height, Unit system

Limitations

BMI uses only height and weight. It does not directly measure body fat, muscle mass, distribution of weight, lab markers, medical risk, pregnancy status, or child/teen percentiles.

Review record

Method and sources checked on July 12, 2026. The documented method, source timing, validity conditions, and reliance limits were checked on this date.

Method provenanceEstimate · toolkitshelf.BMI-adult.v1
Maintained by
Toolkit Shelf
Calculation class
Estimate
Method version
toolkitshelf.BMI-adult.v1
Source date
June 26, 2024
Source checked
July 12, 2026
Intended audience
Adults age 20 and older who want a general BMI screening number from measured height and weight.
Valid when
Use adult inputs, measured height and weight, and the displayed unit conversion. Children, pregnancy, athletes, and individual medical context need different interpretation.
Reliance boundary
BMI is a screening estimate, not a diagnosis, body-fat measurement, treatment recommendation, or substitute for professional medical advice.
Data freshness
The CDC adult categories and screening limitations were checked on July 12, 2026. The internal method version changes only after a material formula or category change.
Cite this page

Toolkit Shelf. BMI Calculator. https://toolkitshelf.com/tools/bmi-calculator

FAQ

Common questions

What is BMI?

BMI stands for body mass index. It compares weight with height to produce a screening number using kg/m² or the equivalent US formula.

Is BMI a medical diagnosis?

No. BMI is a broad screening estimate and should not replace medical advice or a full health assessment.

Does BMI work for athletes?

BMI can be misleading for muscular people because it does not distinguish muscle from fat.

What are BMI's biggest limitations?

BMI does not directly measure body fat, muscle mass, pregnancy status, age-related changes, or individual health risk. It is a screening number, not a diagnosis.

Is BMI interpreted the same for children and adults?

No. Adult BMI categories are for adults 20 and older. Children and teens are interpreted with age and sex percentiles.

When can BMI be misleading?

BMI can be misleading for muscular people, pregnancy, older adults, and some medical situations because it only uses height and weight.