BMI Calculator is a free platform, an easy way to calculate your Body Mass Index Lab Report using height and weight. WHO-standard classification, healthy weight range, and an instant weight-status gauge. Drop your numbers in. Get a report in an instant. No signup, no fluff.
Fill in your stats on the left and run the analysis to view your BMI report.
Body Mass Index (BMI) is a simple screening measure that compares your weight to your height. It does not measure body fat directly, but for most adults it correlates closely enough with body fat to serve as a fast, free starting point for a weight-related health conversation.
BMI takes two inputs, height and weight, and reduces them to a single number using one of the oldest formulas still in everyday medical use. That number is then mapped onto a classification scale set by the World Health Organization, running from underweight through normal, overweight, and three tiers of obesity.
Doctors, insurers, and public health agencies still lean on BMI because it costs nothing, requires no equipment beyond a scale and a tape measure, and takes seconds to compute. It is a screening tool, not a diagnosis. Muscle mass, frame size, age, and sex all shift what a healthy number actually looks like for a given individual.
Two versions of the formula exist, one for metric units and one for imperial. Both produce the same kg/m² result once the unit conversion is applied.
Metric example: a person who is 1.70 m tall and weighs 68 kg has a BMI of 68 ÷ (1.70 × 1.70) = 23.5, which sits in the normal range. The 703 constant in the imperial formula converts pounds and inches into the same kg/m² scale used worldwide, so a US measurement and a metric measurement always land on the same classification.
| BMI Range | Classification | What It Means |
|---|---|---|
| Below 18.5 | Underweight | May indicate insufficient nutrition or an underlying condition |
| 18.5 – 24.9 | Normal Weight | Associated with the lowest average health risk for most adults |
| 25.0 – 29.9 | Overweight | Increased risk of cardiovascular and metabolic conditions |
| 30.0 – 34.9 | Obese Class I | Moderate obesity, elevated health risk |
| 35.0 – 39.9 | Obese Class II | Severe obesity, high health risk |
| 40.0 and above | Obese Class III | Very severe obesity, very high health risk |
These bands come from population-level data and apply most reliably to adults of average frame and muscle mass. Athletes, older adults, and people carrying above-average muscle should read their result alongside body fat percentage rather than BMI alone. Pair this reading with the FFMI Calculator for a fuller composition picture.
Inputs: Height 170 cm = 1.70 m, Weight 68 kg
Verdict: A BMI of 23.53 falls inside the 18.5 to 24.9 normal weight band. For this height, the healthy weight range runs from roughly 53.5 kg to 72.0 kg.
BMI was designed in the 1830s by Belgian statistician Adolphe Quetelet for population-level statistics, not individual diagnosis. It uses only height and weight, which works adequately for sedentary adults of average build but breaks down the moment muscle mass, frame size, or age enter the picture. For a more precise read on lean tissue, pair your BMI result with a Fat-Free Mass Index (FFMI) reading.