Underweight
below 18.5
Health
BMI Calculator
Use this BMI calculator to estimate adult body mass index from height and weight. Choose metric or imperial units, enter your measurements, and review the standard adult BMI category with clear notes about when BMI is useful and when it is limited.
bmibody mass indexhealthweightheightfitness
Calculator
Calculate instantly
BMI = weight (kg) / height (m)^2
Metric and imperial values are first converted to kilograms and meters, then weight is divided by height squared.
- The formula uses metric units, even when the original inputs are imperial.
- Height is squared so weight can be compared consistently across different heights.
- The result is compared with broad adult reference thresholds.
Inputs
Height and weight inputs
Choose a unit system, enter height and weight, and see a standard adult BMI screening reference with a clear visual explanation.
Breakdown
Clear result breakdown
Review the values that explain the primary result.
Normal weight
18.5 to 24.9
Your current reference band
Overweight
25 to 29.9
Obesity range
30 or higher
Visual comparison
BMI reference comparison
Your BMI is shown alongside the standard adult reference thresholds. BMI is a screening measure, not a diagnosis.
Your BMI is shown alongside the standard adult reference thresholds. BMI is a screening measure, not a diagnosis.
Underweightbelow 18.5
Normal weight18.5 to 24.9
Overweight25 to 29.9
Obesity range30 or higher
Your BMI23.5
Practical guidance
Insights for this scenario
A screening value, not a diagnosis
BMI is one broad weight-for-height screening measure. It does not directly measure body composition, fitness, or individual health.
Use context
Age, muscle mass, pregnancy, ethnicity, medical history, and clinical measurements can affect how a BMI value should be interpreted.
Ask when it matters
For a personal health concern, talk to a qualified healthcare professional rather than relying on one calculator result.
Visual reference
Your BMI falls in the Normal weight range
This is the standard reference range commonly used for adult BMI screening.
Step-by-step solution
Follow the calculation path from known values to final result.
- 1
Standardise the measurements
Imperial values convert to kg and m
72 kg and 1.75 m
The formula uses metric units, even when the original inputs are imperial.
- 2
Square the height
height squared = H x H
1.75 x 1.75
Height is squared so weight can be compared consistently across different heights.
- 3
Divide weight by height squared
BMI = W / H^2
72 / 3.063
The result is compared with broad adult reference thresholds.
23.5 - Normal weight
Formula explorer
BMI = weight (kg) / height (m)^2
Metric and imperial values are first converted to kilograms and meters, then weight is divided by height squared.
- W(kg)
- Weight: Body weight converted to kilograms.
- H(m)
- Height: Height converted to meters.
Assumptions and references
Units
- kg
- cm
Assumptions
- This uses the standard adult BMI screening formula.
- The input measurements are accurate and current.
Limitations
- BMI is not a medical diagnosis or direct body-fat measurement.
- Children, teenagers, pregnancy, athletic body composition, and health conditions need specialised assessment.
Worked examples
EasyMetric BMI example
Known values
- Weight: 72 kg
- Height: 175 cm
Calculation
- 1. Convert 175 cm to 1.75 m.
- 2. Square 1.75 m.
- 3. Divide 72 by 1.75 squared.
Result and meaning
BMI is about 23.5, within the standard adult reference range.
Real-worldUse the result with health context
Known values
- A BMI result
- Personal medical or fitness context
Calculation
- 1. Treat the category as a starting screening point.
- 2. Consider body composition and health history.
- 3. Discuss meaningful concerns with a professional.
Result and meaning
A single BMI value is most useful as one input in a wider health conversation.
Learning guide
Understand the calculation
Concepts
- BMI is a weight-for-height screening measure.
- The same formula works worldwide after unit conversion.
- A category describes a reference range, not a personal diagnosis.
Tips
- Use accurate, current measurements.
- Track change over time rather than fixating on a single result.
- Use professional advice for personal health decisions.
Common mistakes
- Using centimetres in the formula without converting to metres.
- Treating BMI as a direct body-fat percentage.
- Using adult thresholds for children or teenagers.
Educational notes
- This calculator provides an estimate only and is not medical advice.
Glossary
- Weight
- Body weight normalized to kilograms.
- Height
- Height normalized to meters before squaring.
Trust panel
Calculator quality and review
- Reviewed by
- AZCalculate health calculator review
- Review date
- 2026-06-25
- References
- 2
- Trust score
- 91/100
- Formula verified
- Yes
- Risk level
- high
- Category
- Health
- Calculator version
- 2.1
- Formula version
- 2.1
Sign in to save this calculation and access it later.
Trust note
Important estimate
BMI is a general adult screening measure only. BMI alone cannot diagnose health, and individual assessment requires qualified professional advice. Children and teenagers require age- and sex-specific assessment, and pregnancy or unusual muscle mass can make standard adult BMI less useful.
High risk contextDifficulty: easyConfidence estimate: 91/100Reviewed 2026-06-25Reviewed by: AZCalculate health calculator reviewCalculator v2.1 / Formula v2.12 sources listed
References
Sources used for this calculator
Last checked: 2026-06-24
Last checked: 2026-06-24
Found something that does not look right?
We work hard to keep every calculator accurate and useful. If you notice a calculation error, missing option, or unclear explanation, please let us know so we can review and correct it promptly.
Calculator usage
Usage information loads after the calculator is ready.
FAQ
BMI Calculator FAQs
Is BMI a medical diagnosis?+
No. BMI is a screening estimate and should not replace guidance from a medical professional.
Does BMI work for athletes?+
BMI can overestimate body fat for muscular people because it does not distinguish muscle from fat mass.
What does BMI measure?+
BMI compares body weight with height using a standard adult screening formula. It does not directly measure body fat or health status.
How do I calculate BMI in metric units?+
Convert height to meters, square the height, then divide weight in kilograms by height squared.
How do I calculate BMI in imperial units?+
The calculator converts pounds, feet, and inches to kilograms and meters before applying the same BMI formula.
What BMI categories are shown?+
The adult reference categories are underweight below 18.5, normal weight from 18.5 to 24.9, overweight from 25 to 29.9, and obesity range at 30 or higher.
Is BMI a diagnosis?+
No. BMI is a general screening estimate and cannot diagnose health, disease, body fat percentage, or fitness.
Why can BMI be less useful for athletes?+
BMI does not separate muscle from fat, so people with high muscle mass can receive a higher BMI even when body composition differs from the average population.
Should children or teenagers use adult BMI categories?+
No. Children and teenagers need age- and sex-specific BMI assessment from pediatric growth references or qualified guidance.
Can pregnancy affect BMI interpretation?+
Yes. Standard adult BMI categories are not designed to interpret pregnancy-related body changes.
What should I do with my BMI result?+
Use it as one screening clue. For personal health concerns, discuss the result with a qualified healthcare professional.
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