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HomeCalculatescience/bmi-calculator

BMI Calculator — Body Mass Index

Calculate BMI from weight and height and see what the result means, including the ranges for underweight, healthy weight, overweight, and obesity.

Health tools disclaimer

Results are educational estimates based on the formulas and inputs shown. They are not medical advice, diagnosis, or treatment. For clinical decisions, medication dosing, or emergency symptoms, consult a licensed healthcare professional.

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Verification & transparency

Automated checks: engine-validated output
Last updated:2026-08-07
|
Sources:WHO 2024 · CDC Growth Charts · Mifflin-St Jeor 1990 · IOM 2009 Weight Gain
|
Reference:bmi = weight / pow(height / 100, 2)
|Rounding & precision policy
Inputs Reference
  • Weight (kg) — range: 20–300
  • Height (cm) — range: 50–250
  • Age (optional) — range: 1–120
  • Body fat % (optional) — range: 0–60
Formula

bmi = weight / pow(height / 100, 2)

On This Page
  • Primary output (BMI)
  • calculatorInputsTitle
  • reverseSolveLabel
  • calculatorFormulaTitle
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Content reviewed by Anoop Kumar

Imperial

Body metrics

BMI24.22Normal weight
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Methodology

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Unit conversions follow SI and common measurement standards. We use careful numeric handling to reduce rounding surprises.

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  • Computation graph
  • Sensitivity analysis
  • BMI decision comparison
  • Result chart
    • Common Questions
    • When is this health estimation context enough?
    • What should I record with the result?
    • When should I use a specialized modifier?
    Related Tools
    • BMI Calculatorhealth

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    © 2026 ExpertToolkit. All rights reserved.

    Release 2.5Market: United States

    Primary output (BMI)

    BMI

    24.2215

    Computed from default inputs using graph `synth-bmi`.

    Calculator inputs

    Weight
    70
    Range: 20 - 300

    Mathematical model

    bmi = weight / pow(height / 100, 2)

    Main equation used by this calculator. Numeric steps follow the page's precision and rounding rules.

    Term Glossary

    Weight (kg)
    Weight (kg) is a declared input for BMI Calculator. Check this value and its unit before reusing the result. Expected values usually stay between 20 and 300.
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    • About Us
    Height
    170
    Range: 50 - 250
    Age
    30
    Range: 1 - 120
    Body fat %
    0
    Range: 0 - 60

    Reverse Solve

    Solve for Weight (kg)

    Weight (kg): 76.9958 for BMI 26.642

    Formula and method

    Standard BMI using metric units.

    bmi=weight(height100)2 bmi=\frac{ weight}{\left(\frac{ height}{100}\right)^{2}}bmi=(100height​)2weight​

    Computation graph

    1. bmiweight / pow(height / 100, 2)

    BMI decision comparison

    BMI decision comparison

    itemvaluenote
    Stress low6.92Weight (kg): 20
    Downside21.8Weight (kg): 63
    Base case24.22Weight (kg): 70
    Upside26.64Weight (kg): 77
    Stress high103.81Weight (kg): 300

    Result chart

    Visual Analysis1 series8 points

    Expanded chart built from the same sensitivity run as the table, so users can read the trend and verify the numbers in one place.

    Trend
    Upward
    Min
    6.9204
    Max
    82.276
    Insight
    BMI shows an upward pattern, with a visible peak around 237.7778 at 82.276.
    6.920425.759344.598263.437182.2762051.111182.2222113.3333144.4444175.5556206.6667237.7778

    Visual response curve for BMI.

    How to use this calculator

    Health tools disclaimer: Educational estimates only, not medical advice, diagnosis, or treatment. For clinical decisions, dosing, or emergencies, follow guidance from US Department of Health & Human Services and a licensed professional in your jurisdiction.

    Body mass index from weight (kg) and height (cm).

    BMI Calculator turns Weight (kg), Height (cm), Age (optional), and Body fat % (optional) into BMI. Confirm the units and assumptions match your situation before relying on the result.

    BMI Calculator produces a screening estimate, not a diagnosis. Measurements such as Weight (kg), Height (cm), Age (optional), and Body fat % (optional) translate into BMI, which is useful for tracking a trend over time or preparing questions for an appointment — not for deciding treatment, dosing, or urgency on its own.

    Estimate quality tracks measurement quality: enter current values, use the units each input asks for, and describe the individual case rather than a population average. If a result would change medication use, urgent care timing, or a treatment decision, stop at the estimate and confirm the next step with a licensed professional.

    Overwhelm from technical jargon

    Start with the basic inputs only — advanced options can be explored once you understand the fundamentals. Important: Don't be discouraged if your results seem unfavorable — these tools help you plan, not judge.

    Enter your values, then check the formula, scenarios, and FAQ to confirm the assumptions fit your case. For medical, financial, legal, or safety-critical decisions, treat the output as an estimate and verify it against the relevant professional standard.

    Sources & Standards

    1. World Health Organization. "Body mass index - BMI." WHO Regional Office for Europe, 2024.BMI classification thresholds: underweight <18.5, normal 18.5-24.9, overweight 25-29.9, obese ≥30
    2. Centers for Disease Control and Prevention. "About Child & Teen BMI." CDC, 2024.Pediatric BMI uses age-sex-specific percentiles, not adult thresholds
    3. Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990;51(2):241-247.BMR formula: 10×weight(kg) + 6.25×height(cm) - 5×age - 161 (female) or +5 (male)
    4. Institute of Medicine. "Weight Gain During Pregnancy: Reexamining the Guidelines." National Academies Press, 2009.Recommended pregnancy weight gain by pre-pregnancy BMI category

    Verify this result

    This answer is computed by CalculationEngine (v1.0.0). The same inputs always produce the same figure and the same fingerprint below, so you can reproduce and cite it.

    Standards

    • WHO 2024 — BMI classification thresholds: underweight <18.5, normal 18.5-24.9, overweight 25-29.9, ob
    • CDC Growth Charts — Pediatric BMI uses age-sex-specific percentiles, not adult thresholds
    • Mifflin-St Jeor 1990 — BMR formula: 10×weight(kg) + 6.25×height(cm) - 5×age - 161 (female) or +5 (male)

    Assumptions

    • Scenariodefault inputs
    • Methodformula-graph evaluation
    • Formulabmi = weight / pow(height / 100, 2)

    Inputs & outputs

    • in · weight70
    • in · height170
    • in · age30
    • in · bodyFat0
    • out · BMI24.221453287197235

    Computation fingerprint (SHA-256)

    6e70bb421406c049e2216739712213383045fceba2cac0618d5679048810cf0f

    Related Tools

    BMI Calculator context FAQ

    When is this health estimation context enough?
    Use it when the result only depends on age, sex, height and no local rule changes the interpretation.
    What should I record with the result?
    Record the input values, reference population, measurement unit, activity estimate, output unit, and rounding rule used in the calculation.
    When should I use a specialized modifier?
    Use a specialized modifier when measurement units, reference range, age/sex context, and non-diagnostic limits materially changes how the same result should be explained.

    Worked Examples — BMI Calculator

    ScenarioInputsResultInterpretation
    Average adult male (US)Weight: 195 lbs (88.5 kg); Height: 5'10" (177.8 cm)BMI = 27.9 — OverweightBMI 25–29.9 is classified as overweight by WHO. However, a muscular male athlete at this weight-height may have 12% body fat (lean), illustrating BMI's limitation for athletic body types.
    Healthy weight woman, metricWeight: 62 kg; Height: 165 cmBMI = 22.8 — Normal weightBMI 18.5–24.9 is the WHO 'normal' range. This is consistent with reduced risk for metabolic diseases, cardiovascular disease, and type 2 diabetes.
    Athlete with high muscle massWeight: 220 lbs (99.8 kg); Height: 6'1" (185.4 cm)BMI = 29.0 — Overweight (misleading)NFL linebacker at 8% body fat — classified 'overweight' by BMI. In such cases, use body fat % (DEXA, skinfold calipers) instead of BMI for accurate health assessment.

    Common Mistakes When Using BMI Calculator

    Using BMI as the sole health metric for athletes or muscular individuals — it will over-classify them as overweight/obese.
    Applying adult BMI categories to children (under 19).
    Height (cm)
    Height (cm) is a declared input for BMI Calculator. Check this value and its unit before reusing the result. Expected values usually stay between 50 and 250.
    Health Calculators
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    • BMR Calculator
    • Body Fat Calculator
    • Ideal Weight Calculator
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    Method & sources

    Each calculator shows its formula and sources on the page.

    X-axis: Weight (kg)Y-axis: BMI
    Reference Tables
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