Maintain your current lifestyle with balanced diet and regular exercise.
BMI Categories
Underweight
16 - 18.5
Healthy Weight
18.5 - 25
Overweight
25 - 30
Obese Class I
30 - 35
Obese Class II
35 - 40
Obese Class III
40 - 40+
About BMI
BMI is a screening tool, not a diagnostic measure. It doesn't account for muscle mass, bone density, age, or ethnicity. Consult a healthcare provider for personalized advice.
Disclaimer: This calculator provides general health information and estimates for educational purposes only. It is not medical advice, a diagnosis, or a treatment recommendation, and it is not a substitute for care from a licensed healthcare provider. Results are based on population formulas and may not reflect your individual health status, medications, or medical conditions. Never use this tool to start, stop, or adjust any medication, treatment, diet, or exercise program without professional guidance. Any drug-dosing results are teaching aids only and must be independently verified against drug-specific protocols and confirmed by a licensed clinician or pharmacist before use. Always consult a physician, pharmacist, or registered dietitian for guidance specific to your situation.
How This Calculator Works
Uses the WHO BMI classification standard with CDC-recommended weight categories. Ranges: underweight (<18.5), normal (18.5-24.9), overweight (25-29.9), obese (30+).
Sources: World Health Organization (WHO), Centers for Disease Control and Prevention (CDC)
Frequently Asked Questions
Q
What is BMI?
Body Mass Index (BMI) is a screening tool that estimates body fat using your height and weight. Formula: BMI = weight (kg) / height (m)². For example, a person weighing 70 kg and 1.75 m tall has a BMI of 22.9 (70 ÷ 1.75² = 22.9), which falls in the healthy range.
Formula (metric): weight (kg) ÷ [height (m)]²
Formula (imperial): [weight (lbs) ÷ height (inches)²] × 703
Used by doctors worldwide as initial health screening
Takes 30 seconds to calculate with our tool
BMI was developed in the 1830s by Belgian mathematician Adolphe Quetlet. While not perfect, it's a quick, inexpensive way to screen for weight categories that may lead to health problems. The CDC and WHO use BMI as a standard health assessment tool.
Q
What is a healthy BMI range?
A healthy BMI ranges from 18.5 to 24.9 for adults. BMI under 18.5 indicates underweight, 25-29.9 is overweight, and 30+ is obese. For example, someone 5'9" should weigh between 125-169 lbs to maintain a healthy BMI.
Underweight (<18.5): Risk of malnutrition, osteoporosis, weakened immunity
Healthy (18.5-24.9): Lowest risk for weight-related disease
Overweight (25-29.9): Increased risk of heart disease and diabetes
Obese Class I (30-34.9): High risk — lifestyle changes recommended
Obese Class II-III (35+): Very high risk — medical consultation advised
BMI Range
Category
Health Risk
Below 18.5
Underweight
Increased
18.5 - 24.9
Healthy Weight
Low
25.0 - 29.9
Overweight
Moderate
30.0 - 34.9
Obese (Class I)
High
35.0 - 39.9
Obese (Class II)
Very High
40.0+
Obese (Class III)
Extremely High
BMI categories are based on extensive research linking weight ranges to health outcomes. Higher BMI increases risk of heart disease, type 2 diabetes, high blood pressure, and certain cancers. According to the National Institutes of Health, maintaining a BMI in the healthy range can significantly reduce these risks.
Q
Is BMI accurate for everyone?
BMI is accurate for most adults but has limitations. It doesn't account for muscle mass, bone density, body composition, or age/sex differences. Athletes with high muscle mass may have "overweight" BMI but low body fat. Elderly people may have "healthy" BMI but insufficient muscle mass.
Not accurate for bodybuilders or athletes (high muscle mass)
May not reflect body fat in elderly (loss of muscle)
Doesn't distinguish between visceral and subcutaneous fat
Asian populations may have health risks at lower BMI (23+)
Children and teens need age-specific BMI percentiles
For example, a muscular athlete weighing 200 lbs at 5'10" has a BMI of 28.7 (technically "overweight"), but their body fat percentage might be just 10%. Conversely, an elderly person with low muscle mass could have a "healthy" BMI but high body fat. Use BMI as one tool alongside waist circumference, body fat percentage, and overall health markers.
Q
How do I calculate my BMI?
Calculate BMI by dividing weight in kilograms by height in meters squared. Metric example: 70 kg ÷ (1.75 m)² = 70 ÷ 3.06 = 22.9 BMI. Imperial example: (154 lbs ÷ 69 inches²) × 703 = (154 ÷ 4,761) × 703 = 22.7 BMI.
Step 1: Measure your weight (without clothes)
Step 2: Measure your height (without shoes)
Step 3: Use our calculator or apply formula
Step 4: Compare result to BMI categories above
Green zone (18.5-24.9): No action needed
Yellow zone (25-29.9): Consider lifestyle changes
Height
120 lbs
140 lbs
160 lbs
180 lbs
200 lbs
5'2" (157 cm)
21.9
25.6
29.3
32.9
36.6
5'4" (163 cm)
20.6
24.0
27.5
30.9
34.3
5'7" (170 cm)
18.8
21.9
25.1
28.2
31.3
5'10" (178 cm)
17.2
20.1
23.0
25.8
28.7
6'0" (183 cm)
16.3
19.0
21.7
24.4
27.1
6'2" (188 cm)
15.4
18.0
20.5
23.1
25.7
Q
What BMI is considered overweight?
BMI of 25.0 to 29.9 is classified as overweight. For someone 5'9" tall, overweight means weighing 170-202 lbs. For 5'4", it's 146-174 lbs. Being overweight increases health risks moderately compared to healthy weight range (18.5-24.9).
Overweight is BMI 25.0-29.9 — a moderate health risk category
Losing 5-10% of body weight can significantly reduce health risks
Waist circumference adds context: >40 in (men) or >35 in (women) = higher risk
Asian populations may face increased risks at lower BMI thresholds (23+)
Height
Healthy Weight
Overweight Range
Obese (30+ BMI)
5'2" (157 cm)
101-136 lbs
137-163 lbs
164+ lbs
5'4" (163 cm)
108-145 lbs
146-174 lbs
175+ lbs
5'7" (170 cm)
118-159 lbs
160-191 lbs
192+ lbs
5'9" (175 cm)
125-168 lbs
169-202 lbs
203+ lbs
6'0" (183 cm)
140-183 lbs
184-220 lbs
221+ lbs
6'2" (188 cm)
148-193 lbs
194-232 lbs
233+ lbs
Example Calculations
1Healthy Weight Adult
Inputs
Weight154 lbs (70 kg)
Height5'9" (175 cm)
Result
BMI22.9
CategoryHealthy Weight
Healthy Range125-168 lbs
Ideal Weight (BMI 22)149 lbs (68 kg)
BMI = 70 / (1.75)² = 70 / 3.0625 = 22.9. This falls in the healthy range (18.5-24.9). Healthy weight range for 5'9": 18.5 × 1.75² = 56.7 kg (125 lbs) to 24.9 × 1.75² = 76.2 kg (168 lbs). Ideal weight at BMI 22: 22 × 3.0625 = 67.4 kg (149 lbs).
2Overweight Example
Inputs
Weight190 lbs (86 kg)
Height5'9" (175 cm)
Result
BMI28.1
CategoryOverweight
To Reach Healthy BMILose 22 lbs
Healthy Range125-168 lbs
BMI = 86 / (1.75)² = 86 / 3.0625 = 28.1. This is in the overweight range (25-29.9). To reach BMI 24.9: 24.9 × 3.0625 = 76.3 kg (168 lbs). Weight to lose: 86 - 76.3 = 9.7 kg (22 lbs). Healthy range: 125-168 lbs.
3Metric Calculation
Inputs
Weight65 kg
Height1.70 m
Result
BMI22.5
CategoryHealthy Weight
Calculation65 ÷ (1.70)² = 22.5
Healthy Range53-72 kg
BMI = 65 / (1.70)² = 65 / 2.89 = 22.5. Healthy range for 1.70m: 18.5 × 2.89 = 53.5 kg to 24.9 × 2.89 = 72.0 kg. Ideal weight (BMI 22): 22 × 2.89 = 63.6 kg.
Formulas Used
BMI Formula (Metric)
BMI = weight (kg) / height (m)²
Standard metric formula used worldwide.
Where:
weight= Body weight in kilograms
height= Height in meters
Source: World Health Organization (WHO) BMI Classification
BMI Formula (Imperial)
BMI = [weight (lbs) / height (in)²] × 703
Imperial formula with conversion factor.
Where:
703= Conversion factor for imperial units
Source: Centers for Disease Control and Prevention (CDC)
Understanding BMI
1
BMI Formula: Metric and Imperial Calculations
BMI divides weight in kilograms by height in meters squared — a 70 kg person at 1.75 m tall scores 22.9, landing in the healthy range of 18.5–24.9. The imperial formula multiplies (weight in lbs ÷ height in inches²) by 703, producing the same result. Both formulas yield a single number that the WHO maps to 7 categories ranging from severely underweight (<16.0) to obese class III (40.0+).
The metric formula is straightforward: BMI = kg / m². For a 5’9″ (175 cm), 190 lb (86 kg) person: 86 ÷ 3.0625 = 28.1, placing them in the overweight category. The imperial version is identical mathematically — (190 ÷ 69²) × 703 = 28.1. Use the body fat percentage calculator alongside BMI for a more complete assessment of body composition.
BMI Range
WHO Category
Risk Level
Example (5’9″)
Below 16.0
Severely Underweight
High
<121 lbs
16.0–16.9
Moderately Underweight
Moderate
121–128 lbs
17.0–18.4
Mildly Underweight
Low–Moderate
129–139 lbs
18.5–24.9
Healthy Weight
Low
140–188 lbs
25.0–29.9
Overweight
Moderate
189–226 lbs
30.0–34.9
Obese Class I
High
227–264 lbs
35.0+
Obese Class II–III
Very High
265+ lbs
2
Why BMI Fails: 2025 Research on Limitations
A 2025 University of Florida Health study found that BMI alone is a poor predictor of mortality risk — individuals with identical BMIs showed widely different health outcomes depending on body composition. The American Medical Association echoed this in 2023, stating BMI should never serve as the sole diagnostic measure for weight-related health assessment.
Consider a 6-foot sprinter weighing 200 lbs: their BMI of 27.1 classifies them as overweight, yet their body fat may be just 8–10%. Conversely, a sedentary person with BMI 23.5 (technically “healthy”) can carry 30%+ body fat with significant visceral fat deposits. Studies estimate BMI misclassifies body fat status in roughly 50% of women and 25% of men.
The core problem is mathematical: BMI uses total weight, making no distinction between muscle, bone, water, and fat. A kilogram of muscle occupies about 18% less volume than a kilogram of fat, so muscular individuals systematically score higher. The Body Roundness Index calculator offers a waist-based alternative that better captures visceral fat distribution.
The AMA recommends using BMI alongside waist circumference, body fat percentage, and metabolic markers — never as a standalone diagnosis.
3
Complementary Body Metrics: BF%, BRI, and BSA
3 metrics fill the gaps BMI leaves. Body fat percentage (measured via the US Navy method at ±3–4% accuracy or DEXA scan at ±1–2% for $50–$150) directly quantifies fat tissue. Athletic men typically range 6–14%, while athletic women range 14–20%. Unlike BMI, body fat percentage correctly classifies muscular individuals.
The Body Roundness Index (BRI) models the torso as an ellipse using only height and waist circumference. A BRI above 6.9 correlates with 49% higher all-cause mortality risk according to Thomas et al. (2013). BRI specifically targets visceral fat — the metabolically dangerous fat around organs that BMI cannot detect. Calculate yours with the BRI calculator.
Body Surface Area (BSA) matters primarily in clinical settings — averaging 1.7 m² for adults — where it determines drug dosing for chemotherapy and cardiac assessments. While less relevant for daily health tracking, BSA paired with BMI helps clinicians evaluate patients more holistically. The BSA calculator uses the Mosteller formula for quick estimates.
Metric
What It Measures
Key Advantage Over BMI
Accuracy
Body Fat %
Actual fat tissue ratio
Distinguishes muscle from fat
±3–4% (Navy) / ±1–2% (DEXA)
BRI
Central body fat (visceral)
Targets dangerous belly fat
r = 0.77 vs DEXA visceral
Waist-to-Height
Central obesity
Simple threshold (>0.5 = risk)
Validated in 300K+ subjects
BSA
Total body surface area
Clinical drug dosing
±2–3% (Mosteller)
4
When BMI Still Works: Population Screening and Trends
Despite individual limitations, BMI remains the most practical screening tool for populations of 1,000+ people where body composition testing is infeasible. The CDC uses BMI to track national obesity trends — the U.S. adult obesity rate rose from 30.5% in 1999 to 41.9% in 2020, a shift BMI captured accurately at scale.
For personal tracking, BMI works best as a trend indicator rather than an absolute number. A BMI rising from 24.0 to 27.5 over 2 years signals meaningful fat gain for most non-athletes, even if the absolute values lack precision. Combined with waist circumference trends and quarterly BMR calculations to track metabolic changes, BMI contributes useful data points to a broader health picture.
5
How to Use This BMI Calculator
Enter your weight and height in either metric (kg/cm) or imperial (lbs/inches) units — the calculator converts automatically. Results include your BMI value, WHO category, healthy weight range for your height, and the distance to the nearest category boundary in pounds or kilograms.
For the most accurate reading, weigh yourself in the morning before eating, wearing minimal clothing. Height should be measured without shoes. Repeat weekly at the same time to track trends rather than fixating on any single reading — daily weight can fluctuate by 2–4 lbs from water retention alone.
1
Enter your weight
Use the unit toggle to switch between lbs and kg. Morning weight before breakfast is most consistent.
2
Enter your height
Switch between feet/inches and centimeters. Measure without shoes against a flat wall.
3
Review your BMI and category
The result shows your BMI, WHO category, healthy weight range, and how far you are from category boundaries.
4
Explore complementary metrics
Use body fat percentage, BRI, or waist-to-height ratio calculators for a fuller health picture beyond BMI alone.
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.
