Calq.

BMI Calculator

Calculate your Body Mass Index (BMI) based on your height and weight.

Your Details

cm
kg

Introduction

Calq.’s BMI Calculator helps adults estimate body mass index (BMI) from height and weight, then classifies the result using standard WHO adult categories. It is designed for anyone who wants a quick, simple screening of weight status. Fitness beginners, people tracking lifestyle changes, and clinicians’ patients who need an at-home check can all benefit from a clear, consistent BMI reading.

How it works

  1. Choose your unit system. Imperial is primary (lbs, ft, in). Metric is available (kg, cm).
  2. Enter your height. In imperial, use feet and inches (for example, 5 ft 9 in). In metric, use centimeters.
  3. Enter your weight in pounds (or kilograms in metric).
  4. Select Calculate. The tool returns your BMI, category, and a healthy weight range for your height.
  5. Review the results and read the tips below to interpret them.

Inputs explained

  • Unit system: Pick imperial (lbs, ft, in) or metric (kg, cm). Using one system avoids conversion errors.
  • Height: Enter barefoot height measured against a wall. Height is squared in the BMI formula, so small errors in height can noticeably change the result.
  • Weight: Use a reliable scale and enter body weight without heavy clothing or items in pockets. Consistency helps when tracking over time.

Results and interpretation

The calculator shows:

  • BMI value: A single number (for example, 23.1) shown to one decimal place.
  • BMI category (WHO adults):
    • Underweight: < 18.5
    • Normal: 18.5-24.9
    • Overweight: 25-29.9
    • Obesity: ≥ 30
  • Healthy weight range for your height: The weight span that corresponds to a BMI of 18.5-24.9 for your exact height, shown in pounds (primary) and kilograms (secondary).

What your category means

  • Underweight: May indicate insufficient energy intake, illness, or other factors. Consider discussing with a healthcare professional.
  • Normal: Typical range for most adults. Lifestyle habits still matter.
  • Overweight: Screening flag for potential health risks; consider diet, activity, sleep, and stress.
  • Obesity: Stronger screening flag for risk; speak with a clinician for personalized guidance.

Method and assumptions

  • BMI definition: BMI is weight relative to height. It does not directly measure body fat.
  • Formulas:
    • Imperial: BMI = 703 × weight(lb) ÷ [height(in)]²
    • Metric: BMI = weight(kg) ÷ [height(m)]², where height(m) = height(cm) ÷ 100
  • Healthy weight range for a given height:
    • Imperial:
      • Minimum healthy weight(lb) = 18.5 × [height(in)]² ÷ 703
      • Maximum healthy weight(lb) = 24.9 × [height(in)]² ÷ 703
    • Metric:
      • Minimum healthy weight(kg) = 18.5 × [height(m)]²
      • Maximum healthy weight(kg) = 24.9 × [height(m)]²
  • Rounding: BMI is shown to one decimal place. Weight ranges are rounded to the nearest whole pound and one decimal kilogram for readability.
  • Scope: Intended for adults (18+). Not designed for children or teens (who require age- and sex-specific percentiles), or for use during pregnancy or immediately postpartum.

Health and fitness context

  • BMI is a screening tool, not a diagnosis. It helps flag potential risk but does not account for muscle mass, body fat distribution, bone density, and ethnic or age-related differences.
  • Additional measures that add context include waist circumference, waist-to-height ratio, body fat estimates, blood pressure, blood lipids, and glucose.
  • Any decision about weight management, nutrition, or medical treatment should consider your full health picture and professional advice.

Tips and strategies

  • Measure carefully:
    • Height: Stand tall, heels together, back against a wall, head level. Record feet and inches accurately.
    • Weight: Use the same scale, same time of day, minimal clothing, after using the restroom.
  • Be consistent: Track BMI over time rather than focusing on a single reading.
  • Pair with other metrics: Note waist circumference and activity levels for a more complete view.
  • Watch for unit mix-ups: Confirm whether you entered pounds vs kilograms and feet/inches vs centimeters.
  • Set realistic goals: If your BMI is outside the normal range, small, sustainable changes in diet, movement, and sleep are more effective than extreme measures.

Example calculations

Example 1 (imperial)

  • Height: 5 ft 9 in (69 in)
  • Weight: 175 lb
  • BMI: 703 × 175 ÷ 69² ≈ 25.8
  • Category: Overweight (25-29.9)
  • Healthy weight range for 5 ft 9 in: about 125-169 lb (≈ 56.8-76.5 kg)

Example 2 (metric)

  • Height: 180 cm (1.80 m)
  • Weight: 75 kg
  • BMI: 75 ÷ 1.80² ≈ 23.1
  • Category: Normal (18.5-24.9)
  • Healthy weight range for 180 cm: about 59.9-80.7 kg (≈ 132.1-177.9 lb)

Frequently asked questions

  1. What is BMI and why is it used?
    BMI estimates weight status by relating weight to height. It is quick, consistent, and useful for population screening, but it is not a measure of body fat or health on its own.

  2. Which BMI range is considered “healthy” for adults?
    A BMI of 18.5-24.9 is considered normal for adults according to WHO criteria.

  3. Is BMI accurate for athletes or older adults?
    BMI can misclassify very muscular people as overweight and may understate health risks in some older adults with low muscle mass. Use BMI alongside other indicators.

  4. How often should I check my BMI?
    Monthly or quarterly is adequate for most people. More frequent checks are unlikely to be informative unless you are following a program under professional guidance.

  5. Does sex affect BMI results?
    Adult BMI categories are the same for men and women. However, body composition and fat distribution differ, so additional measures can be helpful.

Important disclaimer

This BMI Calculator provides general information for adults and is not medical advice. BMI is a screening tool with known limitations and should not be used to diagnose or treat any condition. Always consult a qualified healthcare professional for personalized assessment and recommendations, especially if you are pregnant, have chronic conditions, or have concerns about your weight.

Summary

BMI is a fast way to screen weight status using height and weight. The Calq. BMI Calculator returns your BMI, WHO category, and a healthy weight range for your height in both imperial and metric units. Use the calculator above with your details, track results over time, and combine BMI with other health measures and professional guidance for a fuller picture of your well-being.