ToolHub

BMI Calculator

Body Mass Index with healthy weight range

Units
ft
in
lb

BMI is a screening tool. It does not measure body fat directly and does not account for muscle mass, frame size, or distribution. Use it as one signal among many, not a diagnosis.

23.6BMI

Normal weight (18.5 – 24.9)

1518.5253040+
Healthy weight for your height125 lb – 169 lb
BMI Prime (BMI ÷ 25)0.95

A BMI in the 18.5 to 24.9 range is associated with lower risk of weight-related health conditions for most adults.

BMI categories (adults)

CategoryBMI range
UnderweightBelow 18.5
Normal weight18.5 – 24.9
Overweight25 – 29.9
Obese (Class I)30 – 34.9
Obese (Class II)35 – 39.9
Obese (Class III)40 and above

Quick lookup

BMI ranges for common heights (healthy weight range, 18.5 – 24.9 BMI)

Quick reference for the weight range associated with a 'normal' BMI at each height. Adult ranges only. Use as a screening starting point, not a target.

HeightHealthy lbHealthy kgOverweight atObese at
5'0" (152 cm)97 – 12744 – 58128 lb / 58 kg153 lb / 70 kg
5'2" (157 cm)104 – 13547 – 61136 lb / 62 kg164 lb / 74 kg
5'4" (163 cm)110 – 14450 – 65145 lb / 66 kg175 lb / 79 kg
5'6" (168 cm)118 – 15453 – 70155 lb / 70 kg186 lb / 84 kg
5'8" (173 cm)125 – 16357 – 74164 lb / 74 kg197 lb / 89 kg
5'10" (178 cm)132 – 17360 – 78174 lb / 79 kg209 lb / 95 kg
6'0" (183 cm)140 – 18363 – 83184 lb / 84 kg221 lb / 100 kg
6'2" (188 cm)148 – 19367 – 88194 lb / 88 kg233 lb / 106 kg

These ranges apply to adults 20 and over. Athletes with significant muscle mass often fall above the 'overweight' BMI line without elevated body fat — BMI does not distinguish muscle from fat.

The basics

What is Body Mass Index?

Body Mass Index (BMI) is a single number that compares your weight to your height. It was developed in the 1830s by Belgian statistician Adolphe Quetelet as a way to study populations, then adopted in the 1970s as an individual screening tool by physiologist Ancel Keys. BMI is widely used because it is cheap, fast, and reasonably correlated with body fat at the population level.

BMI is calculated as weight ÷ height². Metric: kg ÷ m². Imperial: (lb × 703) ÷ in². The result puts you into one of six categories ranging from underweight to severely obese.

Reading your result

The BMI categories

Underweight (under 18.5)

May indicate insufficient body mass. Risk for nutrient deficiency, weakened immune system, osteoporosis later in life.

Normal weight (18.5 – 24.9)

Associated with lowest health risk for most adults. Maintain through balanced eating and regular activity.

Overweight (25 – 29.9)

Modestly elevated risk for type 2 diabetes, cardiovascular disease, sleep apnea. A 5-10% weight loss meaningfully reduces these risks.

Obese Class I (30 – 34.9)

Significantly elevated risk. Lifestyle interventions are typically first-line, with medical support recommended.

Obese Class II (35 – 39.9)

High risk. Professional medical guidance is recommended; some patients are candidates for medications or bariatric procedures.

Obese Class III (40+)

Highest risk. Comprehensive medical care is typically warranted. Bariatric surgery is one effective option discussed with a specialist.

Important caveats

The limits of BMI

BMI is a screening tool, not a diagnosis

BMI does not measure body fat directly. It does not distinguish muscle from fat, account for where fat is distributed, or adjust for bone density, age, sex, or ethnicity. A number alone cannot tell you whether you are healthy.

Where BMI works well

  • Population-level studies (where individual variation averages out)
  • Tracking your own weight changes over time at a constant body composition
  • Quick screening when paired with waist circumference and lifestyle context

Where BMI fails

  • Athletes with high muscle mass (often classified 'overweight' or 'obese' despite low body fat)
  • Older adults with sarcopenia (muscle loss can hide unhealthy fat gain)
  • Pregnant or breastfeeding women
  • Children and teens (use BMI-for-age percentiles instead)
  • People with very short or very tall statures (the formula's accuracy decreases at extremes)

What to measure alongside BMI

Waist circumference is the single best at-home complement. A waist over 40 inches (men) or 35 inches (women) is associated with elevated metabolic risk independent of BMI. Body fat percentage (via skinfold calipers, bioelectrical impedance, or DEXA scan) gives a more direct measure of composition.

An alternative view

BMI Prime

BMI Prime is your BMI divided by 25 — the upper end of the healthy range. A BMI Prime of 1.0 means you are right at the upper threshold. Numbers under 1.0 are healthy or underweight; over 1.0 indicates overweight or obesity.

BMI Prime is useful because it is dimensionless and works across all height units. It also makes comparisons easier: BMI Prime 1.2 means you are 20% above the upper healthy threshold, regardless of whether you measure in pounds or kilograms.

What the calculator shows

The healthy weight range

The "healthy weight" range shown is the weight that would put your BMI between 18.5 and 24.9 at your current height. It is calculated by multiplying those BMI values by your height squared:

min healthy weight = 18.5 × height_m²
max healthy weight = 24.9 × height_m²

For a 5'9" (1.75 m) adult: min ≈ 56.7 kg (125 lb), max ≈ 76.3 kg (168 lb). This is the BMI range only. A healthy target weight for you specifically may differ based on body composition, history, and medical context.

Behind the scenes

Privacy and how it runs

No data leaves your device

Your height, weight, age, and sex are processed entirely in your browser. Nothing is sent to a server. The calculator works offline once loaded.

Common questions

What BMI is considered ideal?

For most adults, a BMI between 20 and 22 is associated with the lowest mortality risk in large studies. The full "normal" range (18.5 – 24.9) is healthy for most people; individual targets within that range depend on body composition and health history.

Can I be metabolically healthy with a high BMI?

Yes — there is a concept called "metabolically healthy obesity" where BMI is in the obese range but blood pressure, blood sugar, and cholesterol are all normal. Studies suggest this is less stable than it sounds: many "metabolically healthy obese" people develop metabolic disease within 10-15 years. Use BMI as one of several signals.

Should I aim for a specific BMI number?

Aim for a BMI in the healthy range (18.5 – 24.9) if you are not already there, and combine that with measures of body composition (waist, body fat %), strength, and cardiovascular fitness. Hitting a specific BMI number is not as meaningful as building sustainable habits.

Why is my BMI different from another calculator?

Two reasons. First, rounding — some calculators round inputs before calculating. Second, the imperial formula constant: the exact value is 703.0696 (lb·in² to kg·m²), but most calculators use 703 even. The difference is well under 0.1 BMI points.

Related calculators

If you're tracking health metrics, these related tools cover the rest of the picture.

Last reviewed: · Methodology based on US building code standards, contractor pricing surveys, and manufacturer specifications.

Quick steps

1

Pick your units

Imperial (feet, inches, pounds) or metric (centimetres, kilograms). The numbers stay correct in either system.

2

Enter height and weight

Use your most recent measurements. For best accuracy, weigh yourself in the morning before eating, in light clothing.

3

Read the result

Your BMI, category, healthy weight range for your height, and BMI Prime all appear with a color-coded scale showing where you fall.

Frequently asked questions

What is BMI?

Body Mass Index is a screening measure that compares weight to height. BMI = weight (kg) / height² (m²). It gives a single number to estimate whether your weight is in a healthy range for your height.

What's a healthy BMI?

For most adults, 18.5 to 24.9 is the 'normal weight' range associated with the lowest health risk. Below 18.5 is underweight, 25-29.9 is overweight, and 30+ is obese.

Is BMI accurate?

BMI is a screening tool, not a diagnosis. It does not measure body fat directly, distinguish muscle from fat, or account for distribution. Athletes and very muscular individuals often have high BMI despite low body fat. Use BMI alongside other measures (waist circumference, body fat percentage) for a fuller picture.

What is BMI Prime?

BMI Prime is your BMI divided by 25 (the upper healthy threshold). A BMI Prime of 1.0 means you are exactly at the boundary; 0.74-1.00 is healthy; over 1.00 indicates overweight or obesity.

Does BMI work for children?

Adult BMI ranges do not apply to children and teens. For ages 2-19, percentile-based BMI-for-age charts (from the CDC or WHO) are used instead. This calculator is for adults 20 and over.

How is the healthy weight range calculated?

We multiply both ends of the healthy BMI range (18.5 and 24.9) by your height squared. For a 5'9" adult: minimum healthy weight ≈ 125 lb, maximum ≈ 169 lb.