BMI Calculator

Worked example

Example: 70 kg and 175 cm gives a BMI of about 22.9, in the normal weight range for adults.

When to use this

• General adult BMI screening from height and weight.
• Switching between metric and US units for the same person.
• Tracking BMI category when updating a wellness log.
• Teaching how weight and height combine into one index number.

Common examples

• 70 kg and 175 cm → BMI about 22.9 (normal adult screening range).
• 180 lb and 5 ft 10 in → BMI about 25.8 (borderline overweight category for adults).
• 65 kg and 160 cm → BMI about 25.4—useful when switching from imperial height inputs.
• 62 kg, 168 cm → BMI about 22.0 for metric wellness screening context.
• 200 lb, 5 ft 4 in → BMI about 34.3—compare with metric entry for same person.

Common mistakes

• Treating BMI as a diagnosis rather than a screening number.
• Entering height in centimeters when feet and inches mode is selected.
• Applying adult categories to children or athletes without context.
• Comparing BMI across different unit systems without converting first.

How it works

Computes body mass index from height and weight. Supports metric (kg/cm) and US (lb/ft-in) units. BMI categories are general screening ranges, not medical advice.

Limitations

BMI is a population-level screening metric, not a diagnosis. Athletes, children, and pregnant users need specialized measures.

Privacy and file handling

Your data stays on your device and is not uploaded.

Accuracy & methodology

This section documents how the calculator works, what it leaves out, and when results were last reviewed. Figures are educational estimates—not professional advice—and are not labeled "current" unless tied to automatically updated reference data.

Formula source or methodology

BMI = weight (kg) ÷ height (m)². US units convert lb → kg and ft/in → meters before calculation. Classification uses WHO-style adult cut points: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obesity.

Jurisdiction

International (WHO adult categories)

Unit system

Metric (kg, cm) or US (lb, ft/in)

Rounding method

BMI rounds to one decimal place.

Assumptions

• Adult height and weight snapshot
• Standard BMI formula; not pediatric BMI-for-age

Known omissions

• Not medical advice. Does not diagnose, treat, or replace clinical assessment.
• Athletic/muscular builds, pregnancy, and ethnicity-specific ranges
• Children and teens (use child growth tool instead)
• Waist circumference or body composition

Test cases (automated)

• 70 kg, 175 cm → BMI ≈ 22.9 (normal)
• Invalid height or weight returns an error

Version & last verified

Logic version 1.0. Content and formulas last verified 2026-07-24.

Important notice

This tool provides a general estimate for educational purposes and is not medical advice. Consult a qualified healthcare professional for personal guidance.