BMI Calculator

Last updated: March 28, 2026

This adult BMI calculator turns your height and weight into a BMI score, adult category, healthy weight range, and a simple change-to-range estimate. Use it for quick screening, goal review, and better context before discussing results with a clinician or coach.

Medical Disclaimer

This calculator is for educational screening only. It does not diagnose disease, prescribe treatment, or replace clinician-guided assessment.

Input Form

Main Result

22.9

Healthy weight

Adult category band: 18.5 to 24.9

Healthy weight range

56.7 kg to 76.3 kg

Related Calculators

Formula Explanation

BMI formula

Calculate one BMI value from height and weight

Metric: BMI = weight (kg) / height (m)^2

U.S. customary: BMI = weight (lb) / height (in)^2 × 703

This BMI calculator first converts the entered units into one comparable formula, then calculates a single BMI value. Height is squared because BMI is a weight-for-height ratio rather than a raw weight reading.

Category and range

Interpret the BMI value and derive the healthy range

Underweight: Below 18.5

Healthy weight: 18.5 to 24.9

Overweight: 25.0 to 29.9

Obesity: 30.0 and above

Min healthy weight = 18.5 × height^2

Max healthy weight = 24.9 × height^2

After BMI is calculated, the page maps that value to standard adult screening bands. The healthy weight range is then solved from the same formula at BMI 18.5 and 24.9 for your current height, and any change-to-range number is simply the gap between your current weight and the nearest boundary.

Adult obesity class context

Class 1 obesity: 30.0 to 34.9
Class 2 obesity: 35.0 to 39.9
Class 3 obesity: 40.0 and above

Use Scenarios

Quick screening

Check one adult measurement set before a routine visit

Use the adult BMI calculator when you want a fast weight-for-height screen before an annual exam, medication review, or general fitness check-in.

Target review

Compare today’s weight with a healthy range by height

The BMI calculator helps when a maintenance, loss, or gain goal needs a neutral reference band instead of a vague “healthy weight” estimate.

Shared discussion

Bring one reference point into clinician or coaching conversations

A BMI result can frame the next questions about waist size, body composition, symptoms, and follow-up priorities without treating one number as a diagnosis.

Example Cases

These BMI calculator examples show how the same formulas produce different category, healthy-range, and change-to-range outputs across common adult screening scenarios.

Worked example

Case 1: Healthy-weight adult check

Inputs

70 kg and 175 cm

Computed Results

BMI 22.9 (Healthy weight); healthy range 56.7 kg to 76.3 kg.

Interpretation

The result stays inside the adult healthy-weight band, so the next step is usually trend tracking rather than reacting to one reading.

Decision Hint

Keep follow-up focused on trend, waist measurements, and daily habits instead of chasing a lower BMI for its own sake.

Worked example

Case 2: Above-range screening result

Inputs

85 kg and 170 cm

Computed Results

BMI 29.4 (Overweight); healthy range 53.5 kg to 72.0 kg.

Interpretation

The BMI lands in the adult overweight band, so the healthy-weight interval helps frame how much change would be needed to re-enter 18.5 to 24.9.

Decision Hint

Use the range as a planning reference, then pair it with pace, symptoms, waist trend, and clinician input when risk factors are present.

Worked example

Case 3: Below-range screening result

Inputs

48 kg and 165 cm

Computed Results

BMI 17.6 (Underweight); healthy range 50.4 kg to 67.8 kg.

Interpretation

A below-range BMI can be a prompt to review intake, recent weight change, and medical context rather than treating the number as a diagnosis by itself.

Decision Hint

If low weight is unintentional or accompanied by symptoms, clinician review is more important than self-adjusting toward a generic target.

Boundary Conditions

Adult thresholds only: children and teens need age- and sex-specific BMI percentiles.

BMI is a screening ratio, not a direct body-fat or fat-distribution measurement.

High muscle mass, edema, amputation, and rapid fluid shifts can weaken interpretation.

Pregnancy-specific weight evaluation should follow clinician guidance rather than adult BMI bands.

Every output depends directly on the accuracy of the entered height and weight.

When clinician guidance differs from the calculator, clinician guidance comes first.

Sources & References

CDC - Calculating BMI
Kept to support the metric and U.S. customary BMI formulas, including the unit-conversion basis behind the two equivalent equation forms.
CDC - BMI Categories for Adults
Used for the adult BMI category cutoffs on the page and for the extra obesity-class context kept below the main calculation chain.
CDC - BMI Frequently Asked Questions
Kept for screening limitations, adult-vs-pediatric context, and clarification that BMI is not a direct measure of body fat or clinical risk by itself.
NHLBI - Calculate Your BMI
Used as a corroborating public-health reference for adult BMI interpretation and the healthy-weight framing that sits behind the range shown on this page.

Editorial & Review Information

Reviewed on: 2026-03-28

Published on: 2024-01-05

Author: LumoCalculator Editorial Team

What we checked: Formula math, adult category thresholds, unit conversion logic, healthy-weight derivation, source accessibility, and wording around screening limits.

Purpose and scope: Supports adult weight-for-height screening and planning discussions. Not intended for pediatric growth evaluation, pregnancy-specific care, or treatment decisions.

How to use this review: Treat the calculator as a structured starting point, then add waist measures, body-composition context, symptoms, and clinician guidance before acting on the result.

Frequently Asked Questions

What does the BMI calculator actually measure?

It calculates Body Mass Index from weight and height, then places that number into adult BMI screening bands. It does not directly measure body fat, fat distribution, or fitness level.

Why do metric and imperial inputs give the same BMI result?

The formulas are equivalent once the units are converted correctly. The metric version uses kilograms and meters, while the U.S. customary version uses pounds and inches with the 703 conversion factor.

Why does the healthy weight range depend only on height?

The healthy range shown here is derived by solving the adult BMI formula at 18.5 and 24.9 for your current height. That gives a reference weight interval for the same height, but it does not replace individual body-composition or clinical goals.

Why can two adults with the same BMI need different follow-up?

BMI is only one screening signal. Muscle mass, waist size, age, symptoms, recent weight change, and medical history can make the same BMI number mean different things in real life.

Does the change-to-range number replace a personal target weight?

No. It only shows the shortest weight change needed to cross into the reference BMI band at your current height. Personal targets still depend on symptoms, body composition, pace, and clinician guidance.

When should a BMI result lead to clinician follow-up?

Use the result as a prompt for follow-up, not self-directed treatment. If weight is changing rapidly, symptoms are present, or the BMI result is far outside the healthy range, clinician review should come first.