Check your BMI instantly. Supports metric (kg/cm) and imperial (lbs/ft). Shows your category, healthy weight range, BMI Prime & Ponderal Index — free, no sign-up.
feet
inches
⚠️ This tool is for informational use only. Always consult a healthcare professional for medical advice.
Enter your details and tap Calculate BMI
BMI status meter
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UnderweightNormalOverweightObese
Healthy Weight—
Normal Range18.5 – 24.9
BMI Prime—
Ponderal Index—
Visual BMI Scale
1018.525303545+
Underweight <18.5
Normal 18.5–24.9
Overweight 25–29.9
Obese I 30–34.9
Obese II+ ≥35
Definition
What Is a BMI Calculator?
A BMI calculator is a tool that measures your Body Mass Index — a number derived from your height and weight that gives a quick estimate of whether you fall in a healthy weight range. The World Health Organization and major health institutions around the world use BMI as a standard screening metric for adults to assess the risk of weight-related health conditions.
BMI does not directly measure body fat, but it is a reliable and widely used indicator for population-level health screening. A single number from a BMI calculator can instantly tell you whether you are underweight, normal weight, overweight, or in one of the obese categories — helping you make informed decisions about your diet, exercise, and overall lifestyle.
SolveFlow's free BMI calculator goes a step further by also showing your healthy weight range, BMI Prime, and Ponderal Index — all in one place, with no sign-up required. It supports both metric (kg and cm) and imperial (lbs, feet, and inches) units so it works for users anywhere in the world.
🪶
Underweight
< 18.5
✅
Normal
18.5 – 24.9
⚠️
Overweight
25 – 29.9
🔴
Obese
≥ 30
Formula
BMI Formula — How It Works
The Body Mass Index formula was developed by Belgian mathematician Adolphe Quetelet in the 19th century and has since become the global standard for weight screening. The calculation is straightforward — it divides your weight by the square of your height.
Example: A person who weighs 70 kg and stands 1.75 m tall has a BMI of 70 ÷ (1.75 × 1.75) = 22.9, which falls comfortably in the Normal Weight category.
The BMI Prime value tells you how far above or below the upper normal boundary (25) you currently sit. A BMI Prime of exactly 1.0 means your BMI is precisely 25. Values below 1.0 are within or below the healthy range. The Ponderal Index is similar to BMI but uses the cube of height, making it slightly more accurate for people who are very tall or very short.
Step-by-Step Guide
How to Use This BMI Calculator
SolveFlow's BMI calculator is designed to be fast and simple — results appear in seconds with no account or subscription needed. Here is how to use it:
Choose your unit system. Click the Metric (kg / cm) tab if you know your measurements in kilograms and centimetres. Click Imperial (lbs / ft) if you prefer pounds, feet, and inches.
Select your gender and enter your age. Gender and age provide useful context, especially when interpreting your result and comparing it against healthy weight ranges.
Enter your height and weight. In metric mode, type your height in centimetres (e.g. 170) and weight in kilograms (e.g. 68). In imperial mode, enter feet and inches separately, then your weight in pounds.
Click "Calculate BMI". Your BMI number, category badge, animated gauge, healthy weight range, BMI Prime, and Ponderal Index all appear instantly in the result panel.
Read the visual scale. The colour-coded BMI scale bar below the calculator shows exactly where your number falls — from underweight on the left to severely obese on the right.
Reference Chart
BMI Categories — Full Classification Table
The table below shows the full BMI classification system used by the World Health Organization (WHO) for adults aged 18 and above. Each category corresponds to a different level of health risk.
BMI Range
Category
Health Risk
Below 16.0
Severe Thinness
Very High
16.0 – 16.9
Moderate Thinness
High
17.0 – 18.4
Mild Thinness (Underweight)
Moderate
18.5 – 24.9
Normal Weight
Low (Healthy)
25.0 – 29.9
Overweight
Increased
30.0 – 34.9
Obese Class I
High
35.0 – 39.9
Obese Class II
Very High
40.0 and above
Obese Class III (Morbid Obesity)
Extremely High
A healthy BMI for most adults is between 18.5 and 24.9. However, optimal healthy ranges can vary slightly based on ethnicity, age, and muscle composition. People of South Asian or East Asian descent may have a higher health risk at lower BMI values, and some health organizations recommend adjusted cut-off points for these populations.
Why SolveFlow
Why Use SolveFlow's Free BMI Calculator?
There are many BMI calculators available online, but SolveFlow's tool is built for speed, clarity, and real usefulness — not just a basic number. Here is what makes it stand out:
⚡
Instant Results
No loading screens, no page refreshes. Your BMI appears the moment you click Calculate.
📊
Visual Gauge
An animated semicircle gauge and colour-coded scale bar make your result easy to read at a glance.
🌍
Metric & Imperial
Works with kg/cm for most of the world and lbs/ft/in for users in the US or other imperial regions.
🔒
No Sign-Up Required
Completely free to use. No account, no email, no personal data stored. Just open and calculate.
📱
Mobile-Friendly
Designed for comfortable use on any screen size — phone, tablet, or desktop — with large tap targets.
🧮
More Than Just BMI
Also shows your healthy weight range, BMI Prime, and Ponderal Index — deeper insights in one calculation.
FAQ
Frequently Asked Questions
BMI is calculated by dividing your weight in kilograms by the square of your height in metres. For example, someone who weighs 65 kg and is 1.68 m tall has a BMI of 65 ÷ (1.68 × 1.68) = 23.0, which is in the normal range. If you are using pounds and inches, the formula is: BMI = 703 × weight (lbs) ÷ height² (inches). SolveFlow's BMI calculator handles all of this automatically — just enter your numbers and click Calculate.
A normal or healthy BMI for adults is between 18.5 and 24.9. A BMI below 18.5 is considered underweight, which can indicate insufficient nutrition or other health concerns. A BMI between 25 and 29.9 is overweight, and a BMI of 30 or above falls into the obese range. These thresholds are set by the World Health Organization and are widely used by doctors, nutritionists, and fitness professionals globally.
At a height of 5'7" (approximately 170.2 cm) and a weight of 75 kg, your BMI would be around 25.9, placing you just into the overweight category. The healthy weight range for someone who is 5'7" is roughly 58 to 79 kg (BMI 18.5 to 24.9). However, BMI alone does not account for muscle mass — an athletic person with significant muscle could have the same BMI but a very different body composition. Always consider BMI alongside other health indicators.
On SolveFlow's BMI Calculator, the Metric tab is selected by default. Simply enter your height in centimetres (e.g. 165 for 165 cm) and your weight in kilograms (e.g. 62), then click Calculate BMI. The tool instantly shows your BMI score, category, healthy weight range for your height, BMI Prime, and Ponderal Index. You can also enter your age and gender for a more complete picture. The BMI calculator in kg is the most commonly used format globally and is the same formula used by most hospitals and health clinics.
The standard BMI formula and classification ranges are the same for both men and women. However, body composition differs between sexes — women naturally carry a higher percentage of body fat than men at the same BMI. This means a woman with a BMI of 22 may have a higher body fat percentage than a man with the same BMI. This is why BMI is best used as a starting point, not a definitive health assessment. Pair your BMI result with waist circumference, body fat percentage, and a healthcare professional's guidance for a more complete evaluation.
BMI Prime is your BMI divided by 25 — the upper boundary of the normal weight range. It gives you a simple ratio that shows how close you are to the healthy upper limit. A BMI Prime of 1.0 means your BMI is exactly 25. A value below 1.0 means you are at or below a healthy weight. A value above 1.0 indicates you are above the healthy upper limit. For example, a BMI of 28 gives a BMI Prime of 28 ÷ 25 = 1.12, meaning you are 12% above the upper normal boundary.
This BMI calculator is designed for adults aged 18 and above. For children and teenagers between the ages of 2 and 19, BMI is interpreted using age- and sex-specific percentile charts rather than fixed adult cut-off values. A child in the 85th to 95th BMI percentile for their age and sex is considered overweight, while the 95th percentile and above indicates obesity. The U.S. Centers for Disease Control and Prevention (CDC) offers a dedicated BMI calculator for children and teens based on these growth standards.
Audience
Who Should Use This BMI Calculator?
SolveFlow's BMI calculator is built for anyone who wants a quick, reliable check on their body weight status. You do not need any medical background to use it — the results are explained clearly with colour-coded categories and a visual gauge.
🏃Fitness Enthusiasts
🩺Health Monitors
🎓Students & Researchers
🥗Dieters & Nutrition Seekers
👨👩👧Parents Checking Adults
✈️Travellers (Imperial/Metric)
Whether you are starting a new fitness journey, tracking your weight loss progress, checking your health before a medical visit, or simply curious about where you stand — this tool gives you a clear and immediate answer. It is especially useful for people switching between metric and imperial units, as it handles both with no conversion needed on your part.
Remember that BMI is a screening tool, not a diagnosis. If your BMI falls outside the normal range, speak with a qualified healthcare provider to understand what that means specifically for your health, lifestyle, and goals.