BMI Calculator: Body Mass Index – The Ultimate Guide

Everything you need to know about BMI, how to calculate it, read the BMI chart, and understand what your number means for your long-term health.

BMI

Body Mass Index (BMI) is a simple numerical value calculated from your height and weight. It was developed in the 1830s by Belgian mathematician Adolphe Quetelet and has since become the world's most widely used screening tool to assess whether an individual has a healthy body weight relative to their height.

BMI is not a direct measurement of body fat. Rather, it is a proxy — an estimate — that correlates well with more precise (and expensive) measures of body composition across large populations. Health organizations including the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and the National Institutes of Health (NIH) all use BMI as a standard screening tool.

Key Point: BMI is a screening tool, not a diagnostic measurement. A high or low BMI indicates a need for further assessment — not a diagnosis of any disease. Always consult a healthcare professional for a complete health evaluation.

Why Does BMI Matter?

Excess body weight is one of the leading risk factors for preventable chronic diseases including type 2 diabetes, cardiovascular disease, hypertension, and certain cancers. Because measuring body fat directly requires specialized equipment, BMI provides a practical, cost-free alternative that can flag potential weight-related health risks in seconds.

Conversely, being underweight also carries serious health consequences — from nutritional deficiencies and weakened immunity to reduced bone density and hormonal disruption. BMI helps identify both extremes.

BMI Chart

The BMI chart classifies adults (age 20+) into distinct weight categories based purely on their BMI value, regardless of age, sex, or race. Below is the standard classification system used by the WHO and CDC.

BMI Category	BMI Range (kg/m²)	Health Risk
Severe Thinness	Less than 16	Very High
Moderate Thinness	16.0 – 16.9	High
Mild Thinness	17.0 – 18.4	Moderate
Normal / Healthy Weight	18.5 – 24.9	Minimal
Overweight	25.0 – 29.9	Increased
Obese – Class I	30.0 – 34.9	High
Obese – Class II	35.0 – 39.9	Very High
Obese – Class III	40.0 and above	Extremely High

BMI Chart by Height and Weight

Use the reference chart below to find your BMI category based on your height (in feet/inches) and weight (in pounds).

Height	Underweight (<18.5)		Normal (18.5–24.9)		Overweight (25–29.9)		Obese (30+)
	Min lb	Max lb	Min lb	Max lb	Min lb	Max lb	Min lb	Max lb
5'0"	–	94	95	127	128	152	153	+
5'2"	–	101	102	136	137	163	164	+
5'4"	–	107	108	144	145	173	174	+
5'6"	–	113	114	153	154	184	185	+
5'8"	–	120	121	163	164	195	196	+
5'10"	–	127	128	173	174	208	209	+
6'0"	–	134	135	183	184	220	221	+
6'2"	–	142	143	194	195	233	234	+

Note: These weight ranges are approximate. Use the BMI Calculator below for your precise BMI value based on your exact measurements.

BMI Chart for Children and Teens

For individuals aged 2–19, BMI is interpreted differently. Instead of fixed ranges, a child's BMI is compared against age- and sex-specific growth charts developed by the CDC, producing a BMI-for-age percentile.

Category	Percentile Range
Underweight	Below the 5th percentile
Healthy Weight	5th to below 85th percentile
Overweight	85th to below 95th percentile
Obesity	95th percentile and above

Calculate BMI

BMI is calculated using a straightforward mathematical formula. There are two versions depending on whether you use metric or imperial (US customary) units.

Metric Formula

BMI = Weight (kg) ÷ Height² (m²)

Example: 70 kg ÷ (1.75 m × 1.75 m) = 22.9

Imperial Formula

BMI = (Weight in lbs ÷ Height² in inches) × 703

Example: (154 lbs ÷ 69² inches) × 703 = 22.7

Step-by-Step: How to Calculate BMI Manually

1. Measure Your Height

   Stand straight against a wall without shoes. Record your height in centimeters (metric) or feet and inches (imperial). For metric: convert feet/inches to meters (1 inch = 0.0254 m).

2. Weigh Yourself Accurately

   Use a calibrated digital scale in the morning, before eating, wearing minimal clothing. Record weight in kilograms or pounds.

3. Square Your Height

   Multiply your height in meters by itself. For example: 1.75 m × 1.75 m = 3.0625 m². This is the denominator in the formula.

4. Divide Weight by Height Squared

   Take your weight in kilograms and divide it by the squared height value you calculated above. Round to one decimal place.

5. Interpret Your Result

   Compare your BMI value to the standard categories in the BMI chart above. For context-specific guidance, speak with your healthcare provider.

BMI Calculator for Men

Use the interactive calculator below to instantly calculate your BMI. While the standard formula is identical for all sexes, we've included male-specific context and healthy range guidance so men can better interpret their results.

BMI Calculator

Metric (kg/cm):

• Height (cm): ___________
• Weight (kg): ___________

Imperial (lbs/in):

• Height – Feet: ___________
• Height – Inches: ___________
• Weight (lbs): ___________
• Age (optional): ___________

Formula (Metric): BMI = Weight (kg) ÷ Height² (m²)
Formula (Imperial): BMI = (Weight in lbs ÷ Height² in inches) × 703

BMI Insights for Men

Men typically carry more muscle mass than women, which means BMI can sometimes overestimate body fat in muscular men. A man with significant muscle mass may have a BMI in the "overweight" range despite having very low body fat. For this reason, men should consider complementing BMI with additional measurements such as waist circumference.

• High-Risk Waist Circumference (Men): 40 inches (102 cm)
• Healthy BMI Range for Men: 18.5 – 24.9
• Healthy Body Fat % for Men: Less than 25%

Average BMI for Men by Age

According to data from the National Health and Nutrition Examination Survey (NHANES), the average BMI for adult men in the United States has been rising over recent decades. Here's a general reference:

Age Group	Average BMI (Men)	Typical Category
20–29 years	26.5	Overweight
30–39 years	28.2	Overweight
40–49 years	29.1	Overweight
50–59 years	29.4	Overweight
60–69 years	29.6	Overweight
70+ years	28.0	Overweight

BMI Calculator for Women

The BMI formula is the same for women as for men, but interpreting the results requires female-specific context. Women naturally carry more body fat than men at any given BMI value due to biological and hormonal differences. This section explains how to calculate BMI as a woman, what the numbers mean for your health, and what additional measurements matter most.

BMI Formula for Women

The calculation is identical regardless of sex:

Metric Formula: BMI = Weight (kg) ÷ Height² (m²)

Example: 60 kg ÷ (1.63 m × 1.63 m) = 22.6

Imperial Formula: BMI = (Weight in lbs ÷ Height² in inches) × 703

Example: (132 lbs ÷ 64² inches) × 703 = 22.7

BMI Calculator – Women (Metric)

Metric (kg/cm):

• Height (cm): ___________
• Weight (kg): ___________

Imperial (lbs/in):

• Height – Feet: ___________
• Height – Inches: ___________
• Weight (lbs): ___________
• Age (optional): ___________

Formula (Metric): BMI = Weight (kg) ÷ Height² (m²)
Formula (Imperial): BMI = (Weight in lbs ÷ Height² in inches) × 703

BMI Categories for Women

Although the official WHO and CDC BMI ranges are the same for both men and women, it is important to understand that women's bodies are biologically different. Women have a higher percentage of essential body fat — approximately 10–13% compared to 2–5% for men — which supports hormonal function, reproductive health, and pregnancy. This means that a woman at a BMI of 22 will typically have a higher body fat percentage than a man at the same BMI.

BMI Category	BMI Range (kg/m²)	Typical Body Fat % (Women)	Health Risk
Underweight	Less than 18.5	Less than 20%	High
Normal / Healthy Weight	18.5 – 24.9	20% – 33%	Minimal
Overweight	25.0 – 29.9	33% – 39%	Increased
Obese – Class I	30.0 – 34.9	39% – 44%	High
Obese – Class II	35.0 – 39.9	44% – 48%	Very High
Obese – Class III	40.0 and above	Above 48%	Extremely High

BMI Chart for Women by Height and Weight (lbs)

Find your approximate BMI category using your height and current weight in pounds. These values are calculated using the standard BMI formula.

Height	Underweight (<18.5)		Normal (18.5–24.9)		Overweight (25–29.9)		Obese (30+)
	Min lb	Max lb	Min lb	Max lb	Min lb	Max lb	Min lb	Max lb
4'10"	–	88	89	119	120	143	144	+
4'11"	–	91	92	123	124	147	148	+
5'0"	–	94	95	127	128	152	153	+
5'1"	–	97	98	131	132	157	158	+
5'2"	–	101	102	136	137	163	164	+
5'3"	–	104	105	140	141	168	169	+
5'4"	–	107	108	144	145	173	174	+
5'5"	–	110	111	149	150	179	180	+
5'6"	–	113	114	153	154	184	185	+
5'7"	–	117	118	158	159	190	191	+
5'8"	–	120	121	163	164	195	196	+
5'9"	–	124	125	168	169	202	203	+
5'10"	–	127	128	173	174	208	209	+

Note: These values are the same for men and women since the BMI formula does not differ by sex. The table starts from 4'10" as that is a more common lower height range for adult women.

BMI Insights for Women

Women's BMI results must be understood in the context of several unique biological and lifestyle factors that differ significantly from men:

• Higher natural body fat: Women need more essential body fat for hormonal regulation, reproductive function, and pregnancy. A healthy body fat range for women is 20–33%, compared to 8–20% for men at a similar BMI.
• Pregnancy and postpartum weight: BMI is not applicable during pregnancy. Postpartum BMI should only be assessed after at least 6–12 weeks, and should always be discussed with a healthcare provider.
• Menopause and body fat redistribution: After menopause, women tend to accumulate more abdominal (visceral) fat even without significant BMI changes, increasing cardiovascular risk independently of BMI.
• Bone density considerations: Women are at higher risk of osteoporosis, and being underweight (BMI below 18.5) significantly worsens bone density loss — especially after menopause.
• Eating disorders: Women are disproportionately affected by eating disorders such as anorexia and bulimia. BMI should never be used as a standalone measure for women with a history of disordered eating.

Key Health Numbers for Women

• High-Risk Waist Circumference (Women): Above 35 inches (88 cm)
• Healthy BMI Range for Women: 18.5 – 24.9
• Healthy Body Fat % for Women: 20% – 33%
• Essential Body Fat % for Women: 10% – 13%
• Healthy Waist-to-Hip Ratio (Women): Below 0.85

Average BMI for Women by Age

According to data from the National Health and Nutrition Examination Survey (NHANES), average BMI values for adult women in the United States vary with age. These figures reflect population averages, not ideal targets:

Age Group	Average BMI (Women)	Typical Category
20–29 years	26.8	Overweight
30–39 years	28.4	Overweight
40–49 years	29.5	Overweight
50–59 years	30.1	Obese – Class I
60–69 years	30.4	Obese – Class I
70+ years	29.0	Overweight

BMI and Women's Health Conditions

Certain health conditions in women are directly linked to BMI levels. Understanding these connections empowers women to take preventive action:

• Polycystic Ovary Syndrome (PCOS)
  PCOS is significantly worsened by excess weight. Even a modest 5–10% reduction in body weight can restore hormonal balance and improve menstrual regularity in women with PCOS. A BMI above 25 is strongly associated with more severe PCOS symptoms.
• Breast Cancer
  Postmenopausal women with a BMI above 25 have a higher risk of developing breast cancer, as excess fat tissue produces estrogen, which can fuel certain types of breast cancer growth.
• Gestational Diabetes
  Women who are overweight or obese before or during pregnancy are at significantly higher risk of gestational diabetes, which can affect both mother and baby.
• Osteoporosis
  Women with a BMI below 18.5 are at high risk of low bone density. Underweight women, particularly those who have experienced amenorrhea (absent periods), face accelerated bone loss and stress fractures.
• Cardiovascular Disease
  After menopause, women's cardiovascular risk increases sharply. A BMI above 25, especially combined with central obesity (waist above 35 inches), substantially increases heart disease and stroke risk in women over 50.
• Fertility and Reproductive Health
  Both underweight (BMI < 18.5) and overweight (BMI > 25) women may experience irregular periods and reduced fertility. Achieving a healthy BMI significantly improves ovulation regularity and pregnancy outcomes.

Healthy Weight Range for Women by Height

The table below shows the ideal healthy weight range (BMI 18.5–24.9) for women at various heights in both pounds and kilograms:

Height	Healthy Weight Range (lbs)	Healthy Weight Range (kg)
4'10" (147 cm)	89 – 119 lbs	40.4 – 54.0 kg
4'11" (150 cm)	92 – 123 lbs	41.7 – 55.8 kg
5'0" (152 cm)	95 – 127 lbs	43.1 – 57.6 kg
5'1" (155 cm)	98 – 131 lbs	44.5 – 59.4 kg
5'2" (157 cm)	102 – 136 lbs	46.3 – 61.7 kg
5'3" (160 cm)	105 – 140 lbs	47.6 – 63.5 kg
5'4" (163 cm)	108 – 144 lbs	49.0 – 65.3 kg
5'5" (165 cm)	111 – 149 lbs	50.3 – 67.6 kg
5'6" (168 cm)	114 – 153 lbs	51.7 – 69.4 kg
5'7" (170 cm)	118 – 158 lbs	53.5 – 71.7 kg
5'8" (173 cm)	121 – 163 lbs	54.9 – 73.9 kg
5'9" (175 cm)	125 – 168 lbs	56.7 – 76.2 kg
5'10" (178 cm)	128 – 173 lbs	58.1 – 78.5 kg

Important: These are general reference ranges based on BMI. Individual factors such as muscle mass, bone density, age, and medical history all affect what a truly healthy weight is for any specific woman. Always consult a healthcare provider for personalized guidance.

BMI vs. Other Measurements for Women

Because BMI does not account for how fat is distributed in the body, women are especially encouraged to use complementary measurements for a fuller health picture:

• Waist Circumference: A waist above 35 inches (88 cm) in women indicates excess abdominal fat and elevated risk of heart disease and type 2 diabetes, even at a normal BMI.
• Waist-to-Hip Ratio (WHR): Divide your waist measurement by your hip measurement. A WHR above 0.85 in women is considered high risk by the WHO.
• Body Fat Percentage: A healthy range for women is 20–33%. This can be measured via DEXA scan, hydrostatic weighing, or bioelectrical impedance analysis.
• Waist-to-Height Ratio: Your waist should be less than half your height for optimal cardiovascular health. This measure is increasingly used as a simpler predictor of metabolic risk.

Health Risks by BMI Category

Your BMI category is strongly associated with your risk for a range of chronic conditions. Understanding these risks is the first step toward taking proactive action.

Risks of Being Overweight or Obese (BMI ≥ 25)

• Heart Disease
  Excess fat increases LDL cholesterol, blood pressure, and arterial inflammation — all major heart disease contributors.
• Type 2 Diabetes
  Obesity is the single strongest modifiable risk factor for insulin resistance and type 2 diabetes development.
• Stroke
  Higher BMI is linked to increased blood clotting risk and arterial plaque buildup that can trigger strokes.
• Joint Problems
  Excess weight puts additional stress on weight-bearing joints, accelerating osteoarthritis development.
• Sleep Apnea
  Fat deposits around the upper airway can cause obstruction during sleep, disrupting oxygen delivery.
• Certain Cancers
  Obesity is associated with higher risk for breast, colon, endometrial, kidney, and liver cancers.

Risks of Being Underweight (BMI < 18.5)

• Malnutrition
  Low body weight often accompanies deficiencies in vitamins, minerals, and essential fatty acids.
• Osteoporosis
  Insufficient calcium and low body weight lead to decreased bone density and fracture risk.
• Weakened Immunity
  The immune system requires adequate nutrition to function properly — underweight individuals fall ill more easily.
• Hormonal Issues
  In women, very low BMI can disrupt menstrual cycles; in men, it can lower testosterone levels.

Limitations of BMI

BMI is a useful population-level screening tool, but it has well-documented limitations that make it an imperfect individual health assessment. Experts increasingly recommend using BMI alongside other measurements rather than in isolation.

• Does not measure body fat directly. Two people with identical BMIs can have vastly different body compositions — one may be mostly muscle, the other mostly fat.
• Muscle mass is not accounted for. Athletes and bodybuilders frequently have high BMIs despite having low body fat percentages.
• Age differences are ignored for adults. Older adults tend to have more body fat at the same BMI than younger adults, but BMI cutoffs remain the same.
• Sex differences are not captured. Women naturally carry more body fat than men at any given BMI level. A "normal" BMI means different things for each sex.
• Ethnic variations exist. Research shows that people of Asian descent face higher health risks at lower BMIs than people of European descent. Some guidelines now recommend a lower BMI threshold (23 instead of 25) for Asian populations.
• Where fat is stored matters. Abdominal (visceral) fat is far more dangerous than fat stored in the hips and thighs — but BMI tells you nothing about fat distribution.

Better Together: Combine BMI with waist circumference, waist-to-hip ratio, and body fat percentage for a more complete picture of your health. A waist circumference above 40 inches (102 cm) in men or 35 inches (88 cm) in women signals significantly elevated health risk, regardless of BMI.

Frequently Asked Questions

What is a good BMI for a man?

A BMI between 18.5 and 24.9 is considered healthy for men according to the WHO and CDC. However, athletic men with high muscle mass may have a slightly higher BMI and still be in excellent health. Men should also aim for a waist circumference below 40 inches (102 cm).

Is BMI the same for men and women?

The formula and cutoff ranges are the same for both men and women. However, women naturally have more body fat than men at the same BMI. This means that for equal health risk, some experts argue that BMI cutoffs should differ slightly by sex, though most major health guidelines still use the same ranges.

Can I have a high BMI and still be healthy?

Yes. Someone with significant muscle mass — such as an athlete or bodybuilder — may have a BMI in the overweight or even obese range while having low body fat and excellent cardiovascular health. This is why BMI should always be considered alongside other health markers, not used as a sole indicator.

How often should I check my BMI?

For most adults, checking BMI every 3–6 months is sufficient — or whenever you experience significant weight changes. More frequent monitoring can be useful if you are actively working toward a weight management goal, but obsessive daily tracking can be psychologically counterproductive.

What is BMI Prime?

BMI Prime is your BMI divided by 25 (the upper healthy BMI limit). A BMI Prime of 1.0 means your BMI is exactly 25. Values below 1.0 are in the healthy or underweight range; values above 1.0 indicate overweight or obesity. It allows quick, intuitive interpretation of how far your BMI deviates from the upper healthy threshold.

What BMI is considered dangerously obese?

A BMI of 40 or above is classified as Class III Obesity (also called Severe or Morbid Obesity). At this level, the risk of life-threatening conditions — including heart disease, type 2 diabetes, and certain cancers — is significantly elevated. Immediate medical intervention is typically recommended.

Does BMI work for children?

BMI is calculated the same way for children as for adults, but it is interpreted differently. Children's BMI is compared against age- and sex-specific growth charts (CDC BMI-for-age percentiles) rather than fixed thresholds, because body composition changes significantly as children grow.

Medical Disclaimer: The information on this page, including the BMI calculator and chart, is intended for general educational purposes only and does not constitute medical advice. BMI is a screening tool, not a diagnostic instrument. Always consult a qualified healthcare professional before making any decisions about your health, diet, or fitness regimen. Individual health circumstances vary widely.