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What Is BMI and How Is It Calculated? (Limits Included)

Published October 3, 2026Written and reviewed by Mateuss M.

What Is BMI and How Is It Calculated? (Limits Included) — illustration
In short: BMI = weight (kg) ÷ height (m)². A person 70 kg and 175 cm has BMI 22.9. It is a screening number, not a diagnosis.

The formulas

  • Metric: BMI = kg ÷ m²
  • Imperial: BMI = 703 × lb ÷ in²
70 kg, 175 cm
AnswerBMI 22.9
  • Healthy weight range (18.5–24.9)
  • For adults 20+. Not for children or pregnancy.
Step-by-step working 3 steps
  1. 1
    Convert height to metres
    175 cm ÷ 100 = 1.75 m
  2. 2
    BMI = weight ÷ height²
    70 ÷ 1.75² = 70 ÷ 3.0625 = 22.8571
  3. 3
    Compare with the standard adult ranges
    Healthy weight range (18.5–24.9)

    These are the WHO adult ranges. BMI is a quick screening number, not a diagnosis: it ignores muscle mass, age, sex and body shape.

150 lb, 65 in
AnswerBMI 25.0
  • Healthy weight range (18.5–24.9)
  • For adults 20+. Not for children or pregnancy.
Step-by-step working 2 steps
  1. 1
    BMI = 703 × weight ÷ height²
    703 × 150 ÷ 65² = 105450 ÷ 4225 = 24.9586

    Weight in pounds and height in inches.

  2. 2
    Compare with the standard adult ranges
    Healthy weight range (18.5–24.9)

    These are the WHO adult ranges. BMI is a quick screening number, not a diagnosis: it ignores muscle mass, age, sex and body shape.

The standard adult ranges

BMICategory (WHO adult)
Below 18.5Underweight
18.5 – 24.9Healthy weight range
25.0 – 29.9Overweight range
30.0 and aboveObesity range

What BMI does not show

  • It does not measure body fat or where fat is carried.
  • Muscular people can have a high BMI at a healthy body-fat level.
  • Ranges for children, teens, older adults and some ethnic groups differ.
This article is educational, not medical advice. Talk to a clinician about what any measurement means for you.

Calculate yours

Use the BMI calculator for metric or imperial units, and the unit converter to switch between kilograms and pounds.

Frequently asked questions

Is BMI accurate for athletes?

Often not, because muscle weighs more than fat for the same volume.

Can I use adult ranges for children?

No. Children use age- and sex-specific percentile charts.

Written and reviewed by Mateuss M.

Mateuss M. writes and reviews mathematical content for CalcSolver, focusing on online calculators, formulas, equations, and practical math tools. He reviews calculator functionality, calculation methods, formulas, examples, and explanations to help ensure that each tool is clear, useful, and easy to understand.

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