BMI Calculator
Use this free BMI calculator to work out your body mass index from your height and weight in US or metric units. You will see your adult BMI category, a visual gauge and the healthy-weight range for your height. Everything is calculated in your browser, and nothing you enter is sent or stored.
Enter your details
Your result
Enter your age, height and weight, then press Calculate BMI. Your result, gauge and healthy-weight range will appear here.
- Underweight: below 18.5
- Healthy weight: 18.5 to 24.9
- Overweight: 25 to 29.9
- Obesity Class I: 30 to 34.9
- Obesity Class II: 35 to 39.9
- Obesity Class III: 40 or higher
BMI is a screening measure, not a diagnosis. It does not measure body fat directly and cannot show your overall health on its own.
What Is BMI?
Body mass index, or BMI, is a number that compares your weight with your height. It is a quick screening measure that doctors and public health agencies use to group adults into weight categories. A BMI calculator does the arithmetic for you, so you can see where your measurements fall without working through the formula by hand.
BMI is useful because it is simple and needs only two measurements. It is also limited. It does not measure body fat, it does not show where fat is stored, and it cannot tell muscle from fat. Think of it as a starting point for a conversation about health, not a verdict on it.
How to Calculate BMI
The calculator above does this for you, but the formulas are straightforward. Use the one that matches your units.
- Metric: BMI = weight in kilograms ÷ (height in meters × height in meters)
- US customary: BMI = 703 × weight in pounds ÷ (height in inches × height in inches)
Worked example: a person who is 170 cm tall (1.70 m) and weighs 70 kg has a BMI of 70 ÷ (1.70 × 1.70) = 70 ÷ 2.89, which is about 24.2. Another person who is 5 ft 10 in (70 inches) and weighs 154 lb has a BMI of 703 × 154 ÷ 4,900, which is about 22.1.
How to use this BMI calculator
- Choose US Units, Metric Units or Other Units. Other Units lets you mix, for example, height in centimeters with weight in pounds.
- Enter your age, height and weight.
- Press Calculate BMI. Use Clear to start over.
If you switch units after typing, the calculator converts the numbers you entered instead of reading them as the new unit.
BMI Chart for Adults
For adults aged 20 and older, the Centers for Disease Control and Prevention (CDC) uses the following standard categories, and this BMI calculator for adults applies them.
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity, Class I |
| 35.0 to 39.9 | Obesity, Class II |
| 40.0 or higher | Obesity, Class III |
The same adult categories are used for men and women. This calculator shows your BMI rounded to one decimal place and assigns the category from that displayed value, so what you see always matches the table.
What Your BMI Result Means
The result from any BMI calculator is one piece of information. A BMI in the healthy-weight range does not guarantee good health, and a BMI outside it does not mean you are unwell. The result is one piece of information. Eating patterns, physical activity, sleep, blood pressure, blood sugar, family history and many other factors matter as much or more.
- Underweight (below 18.5): may be worth discussing with a health professional, especially if the weight is unintentional or recent.
- Healthy weight (18.5 to 24.9): sits in the range most commonly associated with lower health risk across populations, though individuals vary.
- Overweight (25 to 29.9) and obesity (30 and above): are associated with a higher chance of certain health conditions on average. A health professional can look at the wider picture, such as waist size, blood tests and lifestyle.
When to seek professional advice
Talk to a doctor or registered dietitian if your BMI is in the underweight or obesity ranges, if your weight has changed quickly without a clear reason, or if you are planning a major change to your eating or exercise habits. Seek advice before changing your diet if you are pregnant, breastfeeding, have an eating disorder or have a medical condition that affects nutrition. Do not use a BMI number alone to start a restrictive diet.
What Is a Healthy Weight Range?
This BMI calculator also works as a simple healthy weight range calculator. For adults, a healthy-weight range for a given height is the span of weights that gives a BMI from 18.5 up to, but not including, 25. It is a mathematical reference based on the adult BMI thresholds, not a personal ideal weight or a target prescribed for you.
- Lower end in kilograms: 18.5 × height in meters squared
- Upper threshold in kilograms: 25 × height in meters squared
- Lower end in pounds: 18.5 × height in inches squared ÷ 703
- Upper threshold in pounds: 25 × height in inches squared ÷ 703
Taller people have a higher range because the formula squares height. The table below shows example ranges for common adult heights, with weights at BMI 18.5 and BMI 24.9, rounded to the nearest whole number.
| Height | Weight in pounds | Weight in kilograms |
|---|---|---|
| 4 ft 10 in (147 cm) | 89 to 119 lb | 40 to 54 kg |
| 4 ft 11 in (150 cm) | 92 to 123 lb | 42 to 56 kg |
| 5 ft 0 in (152 cm) | 95 to 128 lb | 43 to 58 kg |
| 5 ft 1 in (155 cm) | 98 to 132 lb | 44 to 60 kg |
| 5 ft 2 in (157 cm) | 101 to 136 lb | 46 to 62 kg |
| 5 ft 3 in (160 cm) | 104 to 141 lb | 47 to 64 kg |
| 5 ft 4 in (163 cm) | 108 to 145 lb | 49 to 66 kg |
| 5 ft 5 in (165 cm) | 111 to 150 lb | 50 to 68 kg |
| 5 ft 6 in (168 cm) | 115 to 154 lb | 52 to 70 kg |
| 5 ft 7 in (170 cm) | 118 to 159 lb | 54 to 72 kg |
| 5 ft 8 in (173 cm) | 122 to 164 lb | 55 to 74 kg |
| 5 ft 9 in (175 cm) | 125 to 169 lb | 57 to 76 kg |
| 5 ft 10 in (178 cm) | 129 to 174 lb | 58 to 79 kg |
| 5 ft 11 in (180 cm) | 133 to 179 lb | 60 to 81 kg |
| 6 ft 0 in (183 cm) | 136 to 184 lb | 62 to 83 kg |
| 6 ft 1 in (185 cm) | 140 to 189 lb | 64 to 86 kg |
| 6 ft 2 in (188 cm) | 144 to 194 lb | 65 to 88 kg |
| 6 ft 3 in (190 cm) | 148 to 199 lb | 67 to 90 kg |
| 6 ft 4 in (193 cm) | 152 to 205 lb | 69 to 93 kg |
Limitations of BMI
BMI is a population-level screening tool, so any BMI calculator has well-known limits for individuals.
BMI and muscle mass
BMI uses total weight, so it cannot tell muscle from fat. A muscular person, such as someone who lifts weights regularly, can have a BMI in the overweight range without carrying excess body fat. The reverse can also happen: a person with low muscle mass may have a BMI in the healthy range while carrying more body fat than expected.
Age, body shape and background
BMI does not show where fat is stored, and it does not account for age-related changes in muscle and bone. Some health guidelines also suggest different cut-off points for certain populations. If you are unsure how to read your result, ask a health professional who knows your history.
Children and teenagers
The adult categories above are not used for children and teenagers aged 2 to 19. Their bodies change as they grow, so BMI is interpreted using BMI-for-age percentiles that compare a child with others of the same age and sex. The CDC provides growth charts for this purpose. Because this calculator does not include validated pediatric reference data, it shows a number only for ages 2 to 19 and does not label it. A pediatrician or other health professional can plot the result on a growth chart and explain it. BMI is not interpreted by this tool for children under 2.
Frequently Asked Questions
What is BMI?
BMI stands for body mass index. It is a number calculated from your weight and height that is used to screen for weight categories in adults.
How do I calculate my BMI?
Divide your weight in kilograms by your height in meters squared, or multiply your weight in pounds by 703 and divide by your height in inches squared. The BMI calculator above does this automatically.
What is a healthy BMI for adults?
For adults aged 20 and older, a BMI from 18.5 to 24.9 is classed as a healthy weight by the CDC.
Is BMI the same for men and women?
The adult formula and the adult categories are the same for men and women. Body composition differs between individuals, so the same BMI can reflect different amounts of body fat.
Can BMI be inaccurate for muscular people?
Yes. BMI cannot separate muscle from fat, so people with a lot of muscle can have a high BMI without excess body fat.
Can I calculate BMI using pounds and feet?
Yes. This BMI calculator accepts pounds, feet and inches. Choose US Units and enter your height in feet and inches and your weight in pounds. The Other Units option lets you mix unit types.
What is a healthy weight range for my height?
It is the span of weights that gives a BMI from 18.5 up to below 25 at your height. The calculator shows this range after you press Calculate BMI. It is a reference, not a personal target.
Is BMI suitable for children and teenagers?
Not in the adult form, and this BMI calculator does not label results for ages 2 to 19. For ages 2 to 19, BMI is interpreted using age- and sex-specific percentiles from growth charts, ideally with a health professional.
Does BMI diagnose obesity or other medical conditions?
No. BMI is a screening measure. A health professional makes any diagnosis after considering other measurements, your history and, where needed, tests.
How often should I calculate my BMI?
There is no required schedule. Many people check it occasionally, for example when their weight or goals change. Avoid checking it so often that it becomes stressful, since day-to-day weight shifts are normal.
Sources and Related Tools
- CDC: Adult BMI Categories
- CDC: Child and Teen BMI Categories
- NIH National Library of Medicine (StatPearls): Physiology, Body Mass Index
- Calorie Calculator for an estimate of your daily energy needs
Medical disclaimer: This calculator and article are for general education only and are not medical advice. They are not a diagnosis or a substitute for care from a qualified health professional. Speak with a doctor or registered dietitian before making major changes to your eating or activity.