BMI Calculator

Body mass indexhealthy weight · adult screening · 56.7-76.3 kg range · BMI Prime 0.91

18.524.930

WeightkgHeightcmAgeyearsContext

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Your numbers, formula and explanation together

BMI Calculator - Adult Body Mass Index, Waist Check, Healthy Weight Range & BMI Prime: 22.86 kg/m². healthy weight · adult screening band · healthy range 56.7-76.3 kg · BMI Prime 0.91 · Ponderal Index 13.06 kg/m³

Formula applied

The exact method behind this answer

CalculationTime keeps the method visible so the number can be checked instead of blindly trusted.

Metric BMI = weight kg ÷ height m². US BMI = 703 × weight lb ÷ height in². Waist-to-height ratio = waist circumference ÷ height using the same unit. Healthy-weight range = BMI boundary × height m². BMI Prime = BMI ÷ 25. Ponderal Index = weight kg ÷ height m³.

Apply the formulaMetric BMI = weight kg ÷ height m². US BMI = 703 × weight lb ÷ height in². Waist-to-height ratio = waist circumference ÷ height using the same unit. Healthy-weight range = BMI boundary × height m². BMI Prime = BMI ÷ 25. Ponderal Index = weight kg ÷ height m³.22.86 kg/m²healthy weight · adult screening band · healthy range 56.7-76.3 kg · BMI Prime 0.91 · Ponderal Index 13.06 kg/m³

Your live breakdown

Current inputs in the calculation

These values come from the controls above and update when the calculator changes.

Unit mode: Metric: kilograms + centimetres
Age: 30 years
Sex for context: Female
Metric weight: 70 kg
Metric height: 175 cm
Metric waist: 86 cm
US weight: 154 lb
Height feet: 5 ft

Resulting answer

22.86 kg/m²

healthy weight · adult screening band · healthy range 56.7-76.3 kg · BMI Prime 0.91 · Ponderal Index 13.06 kg/m³

Answer: 22.86 kg/m²
Live support: healthy weight · adult screening band · healthy range 56.7-76.3 kg · BMI Prime 0.91 · Ponderal Index 13.06 kg/m³

Assumptions used

What this answer assumes

BMI is rounded to two decimals. Healthy-weight boundaries use BMI 18.5-24.9 and are rounded to one decimal in the selected unit system.

The calculator supports metric BMI arithmetic and the equivalent US customary formula using the 703 conversion factor.
Height must be greater than zero because the formula divides by height squared.
Adult BMI categories are screening categories for adults aged 20 and over, not a diagnosis or individual health assessment.
The healthy-weight range uses common adult BMI boundaries of 18.5 to 24.9 and is rounded for practical display.
Waist-to-height ratio is shown as a screening context marker; a common public-health guide is to keep waist circumference below half of height, but individual interpretation varies.
BMI can be misleading for children, pregnancy, athletes, older adults and people with unusual body composition; use clinical guidance for health decisions.

Master’s Tip

How to use the result well

Master’s Tip: keep BMI, waist measurement, category, height, weight, age context, healthy-weight range and the “not a diagnosis” limitation together. BMI is useful as a quick screening index, but waist measurement, body composition, pregnancy status, ethnicity, medical history and clinician judgement can change the interpretation.

Printable record

What belongs in the saved calculation

Save the inputs, result, formula, assumptions, page URL and date together so the calculation can be reviewed later.

Unit mode: Metric: kilograms + centimetres
Age: 30 years
Sex for context: Female
Metric weight: 70 kg

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BMI reference

Category table, waist check and visual proof

BMI pages are too thin when they stop at a single number. Use the table, chart and waist-to-height guide together: BMI gives the height-weight index; waist measurement adds abdominal-fat context.

Common adult BMI screening bands
Category	BMI	Read with
Underweight	Below 18.5	Use clinical context before treating this as a target.
Healthy weight	18.5 to 24.9	Common adult screening band.
Overweight	25.0 to 29.9	Waist measurement can change the risk discussion.
Obesity	30.0 and above	Screening flag, not a diagnosis by itself.

Adults use BMI bands; children and teenagers need age-and-sex percentiles.
Waist-to-height around 0.50 is a simple public-health context check.
Muscle mass, pregnancy, illness, ethnicity and medical history can change interpretation.

Waist-to-height0.50 guide

Adult category scale18.5 / 25 / 30

Interpretation splitnumber + context

Formula

Metric BMI = weight kg ÷ height m². US BMI = 703 × weight lb ÷ height in². Waist-to-height ratio = waist circumference ÷ height using the same unit. Healthy-weight range = BMI boundary × height m². BMI Prime = BMI ÷ 25. Ponderal Index = weight kg ÷ height m³.

Worked example

For 154 lb, 5 ft 9 in and a 34 in waist: total height is 69 in. BMI = 703 × 154 ÷ 69² = 22.74 kg/m². Waist-to-height ratio = 34 ÷ 69 = 0.49, just below the common 0.50 guide.

Professional note

Regional and unit assumptions

Standard or basis: this page uses the common adult BMI formula and widely used adult screening bands: under 18.5, 18.5-24.9, 25.0-29.9 and 30.0 or above. It also shows waist-to-height ratio, BMI Prime against 25 and Ponderal Index as context checks. It does not provide diagnosis, treatment or personalised health advice.

Assumptions and limitations

The calculator supports metric BMI arithmetic and the equivalent US customary formula using the 703 conversion factor.
Height must be greater than zero because the formula divides by height squared.
Adult BMI categories are screening categories for adults aged 20 and over, not a diagnosis or individual health assessment.
The healthy-weight range uses common adult BMI boundaries of 18.5 to 24.9 and is rounded for practical display.
Waist-to-height ratio is shown as a screening context marker; a common public-health guide is to keep waist circumference below half of height, but individual interpretation varies.
BMI can be misleading for children, pregnancy, athletes, older adults and people with unusual body composition; use clinical guidance for health decisions.

Trust boundary

What this calculator does NOT do

Diagnosing weight status, disease risk or treatment needs
Replacing clinician advice, growth charts, pregnancy care or body-composition assessment
Setting a personalised target weight without medical context

When to stop using this calculator

Use child and teen BMI percentiles, not adult bands, for anyone under 20.
Ask a qualified professional before using BMI to make health decisions during pregnancy, serious illness, eating-disorder risk, athletic training or major weight change.
Consider waist measurement, ethnicity, medication, fitness, muscle mass and medical history before interpreting the number.

Methodology & Accuracy

How this calculator is checked

CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.

Formula used

Standard or basis

Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.

Master's Tip

Questions

How do you calculate BMI?

In metric units, divide weight in kilograms by height in metres squared. In US units, multiply pounds by 703 and divide by height in inches squared.

What is a healthy BMI range for adults?

Common adult screening bands place 18.5 to 24.9 in the healthy-weight range, but individual health needs clinical context.

What healthy weight range does this calculator show?

It multiplies height squared by BMI 18.5 and 24.9 to show the approximate adult weight range that maps to the common healthy-weight BMI band.

What is BMI Prime?

BMI Prime is BMI divided by 25. A BMI Prime of 1.00 sits at the common adult overweight threshold.

Why include waist measurement with BMI?

Waist measurement adds abdominal-fat context that BMI alone misses. The calculator shows waist-to-height ratio because many public-health explanations use half your height as a simple screening guide.

What is Ponderal Index?

Ponderal Index divides weight in kilograms by height in metres cubed. It is a secondary body-size index sometimes used as a cross-check because BMI can scale imperfectly at very short or very tall heights.

Is BMI a diagnosis?

No. BMI is a simple screening measure. It does not directly measure body fat, fitness, muscle mass, pregnancy status or individual medical risk.

Can children use this BMI calculator?

The arithmetic can be calculated, but children and teenagers need age-and-sex BMI percentile charts rather than adult BMI category bands.

Calculation note

BMI is a compact height-and-weight index. It is useful because the formula is simple and repeatable, but a competitive calculator must also show units, category, healthy range and limitations so the number is not mistaken for a diagnosis.

BMI is an index, not a direct body-fat measurement

BMI compares weight with height squared. That makes it easy to calculate across large groups, but it does not directly measure body fat, muscle, bone density or individual health risk.

Adult category bands are screening bands

Public-health pages commonly present adult BMI bands such as underweight, healthy weight, overweight and obesity. Those bands can help with screening and education, but personal interpretation should consider age, sex, ethnicity, medical history, waist measurement, body composition and professional advice.

Healthy weight range is a formula range, not a prescription

The healthy-weight range on this page reverses the BMI formula using the common adult 18.5-24.9 band. It is useful for education and context, but it is not a personalised target weight or medical instruction.

Waist measurement adds heart-health context

Two adults can have the same BMI but different abdominal-fat patterns. Waist circumference and waist-to-height ratio help flag central weight distribution, which is why a useful BMI page should not stop at height and weight alone.

BMI Prime and Ponderal Index add context

BMI Prime compares the result with the adult overweight threshold of 25. Ponderal Index divides weight by height cubed and gives a second body-size cross-check. Both help explain the number, but neither replaces clinical assessment.

Sources and further readingCDC: About Adult BMI Heart Foundation: What waist measurements mean for your heart WHO: Body mass index - BMI