Health

BMI Calculator (Body Mass Index)

Calculate your BMI with weight and height: WHO category, healthy weight range, and how far you are from it. Instant results, no sign-up required.

Data verified · July 2026
Edited by Martín Rodríguez
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Edited by: Martín Rodríguez (editorial policy )

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BMI, or Body Mass Index, is the most widely used indicator in the world to assess whether your weight falls within a healthy range for your height. It was defined by Adolphe Quetelet in 1832 and adopted by the World Health Organization as a global standard in 1997. With this calculator, enter your weight in kilograms and your height in centimeters, and you'll instantly get your BMI, the WHO category (underweight, normal, overweight, or obesity grades I, II, or III), and the healthy weight range for your height. It works for adults between 18 and 65 years old, requires no registration, and the calculation runs entirely in your browser — your data never leaves your device.

When to use this calculator

You want to know if your current weight falls within the healthy range recommended by the WHO.
You're about to start a diet and want an objective baseline.
You had a medical checkup and want to understand what the BMI in your report means.
You go to the gym and want a baseline number to track your progress over time.
You're a parent and want to understand how weight is assessed during medical consultations.

Healthy Weight Range by Height (lb), with Overweight & Obesity Thresholds

Body weight in pounds for each height, computed from the WHO/CDC adult BMI cutoffs (healthy 18.5–24.9, overweight at BMI 25, obesity at BMI 30) using BMI = lb ÷ in² × 703. Orientative only and not a diagnosis — muscle mass, age, and fat distribution also matter; consult a clinician for a full assessment.

Height	Healthy range (lb)	Overweight at (lb)	Obesity at (lb)	BMI formula
4'10" (58 in)	89 – 119	120+	144+	lb ÷ in² × 703
5'0" (60 in)	95 – 128	128+	154+	lb ÷ in² × 703
5'2" (62 in)	101 – 136	137+	164+	lb ÷ in² × 703
5'4" (64 in)	108 – 145	146+	175+	lb ÷ in² × 703
5'6" (66 in)	115 – 154	155+	186+	lb ÷ in² × 703
5'8" (68 in)	122 – 164	164+	197+	lb ÷ in² × 703
5'10" (70 in)	129 – 174	174+	209+	lb ÷ in² × 703
6'0" (72 in)	136 – 184	184+	221+	lb ÷ in² × 703
6'2" (74 in)	144 – 194	195+	234+	lb ÷ in² × 703

How it works

What Is BMI?

The Body Mass Index (BMI) is a formula created in 1832 by Belgian mathematician Adolphe Quetelet and adopted by the World Health Organization (WHO) in 1997 as the most widely used global indicator of nutritional status in adults. Today, doctors, nutritionists, and health organizations worldwide use it to quickly assess whether a person is within a healthy weight range.

How BMI Is Calculated

BMI = weight (kg) / height² (m)

Weight is in kilograms and height is in meters, squared. If you measure height in centimeters, divide by 100 first: 170 cm = 1.70 m.

WHO Category Table

BMI	Category	Risk
< 18.5	Underweight	Increased
18.5 – 24.9	Normal weight ✅	Low
25.0 – 29.9	Overweight	Increased
30.0 – 34.9	Obesity grade I	Moderate
35.0 – 39.9	Obesity grade II	High
≥ 40.0	Obesity grade III (morbid)	Very high

Healthy Weight by Height (Approximate)

Height	Min Weight	Max Weight
1.50 m	41.6 kg	56.0 kg
1.55 m	44.4 kg	59.8 kg
1.60 m	47.4 kg	63.7 kg
1.65 m	50.4 kg	67.8 kg
1.70 m	53.5 kg	71.9 kg
1.75 m	56.6 kg	76.2 kg
1.80 m	59.9 kg	80.6 kg
1.85 m	63.3 kg	85.2 kg
1.90 m	66.8 kg	89.9 kg

When BMI Doesn't Work Well

Athletes and very muscular people: muscle weighs more than fat. A rugby player at 95 kg and 1.80 m has a BMI of 29.3 (overweight) without actually being overweight.

Adults over 65: the WHO suggests shifting the healthy range to 23–28 because age-related muscle loss means a 'normal' BMI may hide sarcopenia.

Children and adolescents: age- and sex-adjusted BMI percentiles (WHO growth charts) are used instead.

Pregnant women: BMI doesn't apply during pregnancy. The OB/GYN follows a specific weight-gain range.

Health Risks of Being Overweight or Obese

A BMI above 25 sustained over time is associated with a higher likelihood of:

Type 2 diabetes and insulin resistance.

High blood pressure and cardiovascular disease (heart attack, stroke).

High cholesterol and triglycerides (dyslipidemia).

Sleep apnea and breathing problems.

Osteoarthritis from extra load on knees and hips.

Non-alcoholic fatty liver disease.

Higher risk of some cancers (breast, colon, endometrial).

Gallstones and digestive problems.

Risk doesn't depend on BMI alone: abdominal fat predicts cardiometabolic risk better than total weight.

Health Risks of Being Underweight

A BMI below 18.5 is not harmless either and is associated with:

Nutrient deficiencies (iron, calcium, vitamins) and anemia.

Weakened immune system and more infections.

Osteoporosis and higher fracture risk.

Muscle loss (sarcopenia) and fatigue.

Hormonal and menstrual-cycle changes.

Fertility problems.

If your BMI is persistently low, a medical evaluation is worthwhile to rule out underlying causes.

BMI Prime and Ponderal Index: Two Complementary Metrics

Beyond the classic BMI, this calculator also returns two indicators used by professional tools:

BMI Prime = BMI ÷ 25. It's the ratio of your BMI to the upper limit of the healthy range. A value of 1.00 means you're exactly at the edge; below 1 means you're within the healthy range and above 1 means you're over it. For example, a BMI Prime of 1.20 reflects a BMI 20% above the healthy maximum.

Ponderal index = weight ÷ height³ (kg/m³). Unlike BMI (which squares height), the ponderal index cubes it, making it more reliable for very tall or very short people, where BMI tends to distort. The approximate normal range is 11 to 15 kg/m³.

Common Mistakes When Calculating BMI

1. Using height in centimeters: classic error. 170 cm² is not 1.70 m². Always convert to meters.
2. Weighing at different times: weight can vary 1–2 kg between morning and night. Weigh yourself fasting and always at the same time.
3. Treating it as a diagnosis: BMI is a signal, not a diagnosis. Add body fat percentage, waist circumference, and blood tests for a full picture.
4. Comparing BMI between people: two individuals with the same BMI can have very different body compositions.

Beyond BMI: Useful Complements

Body fat percentage (US Navy or Jackson-Pollock method)

Waist circumference: >88 cm in women or >102 cm in men is a risk factor.

Daily calories (TDEE) to know how much to eat based on your goal.

Basal metabolic rate (BMR) using the Mifflin-St Jeor formula.

For a complete assessment, consult a registered dietitian or physician. BMI is a good starting point, not the final picture.

Example: Woman, 1.65 m and 68 kg

Data: weight = 68 kg, height = 1.65 m.

Formula: BMI = weight / height² = 68 / (1.65 × 1.65) = 68 / 2.7225.

Result: BMI = 24.98.

WHO Category: Normal weight (range 18.5 – 24.9), at the upper boundary.

Healthy weight range for 1.65 m: between 50.4 kg and 67.8 kg.

BMI 24.98 — within the healthy range but just 0.2 kg from entering overweight. A maintenance plan would be sufficient.

Disclaimer: For guidance only; this does not replace diagnosis, treatment, or professional follow-up. Consult a licensed healthcare professional.

Frequently asked questions

What is a healthy BMI?

According to the WHO, a healthy BMI for adults is between 18.5 and 24.9. Below that is considered underweight, and above it is overweight. Starting at 30, you enter obesity in its various grades (I, II, and III).

Is BMI the same for men and women?

Yes. The WHO uses the same range (18.5 – 24.9) for both sexes in adults. The difference in body composition between men and women is assessed with other indicators like body fat percentage.

How much should I weigh for my height?

Multiply your height in meters squared by 18.5 (minimum weight) and by 24.9 (maximum weight). For example, for 1.70 m: minimum 53.5 kg, maximum 72 kg. The calculator shows this automatically.

How much can my BMI vary in a day?

Very little in BMI terms, because daily weight varies 1–2 kg (due to fluids and food). But if you weigh yourself at the same time (ideally fasting), your BMI is stable. For tracking, the important thing is the weekly or monthly trend.

Why can an athlete have a high BMI without being overweight?

Because muscle weighs more than fat. BMI doesn't distinguish between muscle mass and fat mass. Rugby players, bodybuilders, and powerlifters often score 'overweight' or 'obese' on BMI but have a low body fat percentage. For them, body fat percentage is a much more useful indicator.

Does BMI work for people over 65?

The WHO suggests expanding the healthy range to 23 – 28 for those over 65 because maintaining slightly more weight protects against sarcopenia (age-related muscle loss). A very low BMI in older adults is associated with higher mortality.

What are the limitations of BMI as a health indicator?

BMI does not account for body composition (muscle vs. fat), fat distribution (visceral vs. subcutaneous), age, ethnicity, or fitness level. Two people with identical BMIs can have vastly different health profiles. That's why healthcare professionals use BMI alongside other measurements like waist circumference, body fat percentage, and blood markers.

What is BMI Prime and what is it for?

BMI Prime is your BMI divided by 25 (the upper limit of the healthy WHO range). A value of 1.00 means you're right at the edge between normal weight and overweight; below 1 means you're within the healthy range and above 1 means you're over it. For example, a BMI of 30 gives a BMI Prime of 1.20 — 20% above the healthy maximum. It's useful because it shows at a glance how far you are from the limit.

What is the ponderal index and how does it differ from BMI?

The ponderal index (or Rohrer index) is weight ÷ height³ (kg/m³), while BMI uses height². By cubing height, the ponderal index is more reliable for very tall or very short people, where classic BMI tends to over- or underestimate. The approximate normal range is 11 to 15 kg/m³. It doesn't replace BMI but complements it, especially at the extremes of height.

Sources & references

WHO - Obesity and Overweight
CDC - About Adult BMI
National Institutes of Health (NIH)

Methodology & trust

Editorial

Health calculator with its formula verified automatically against WHO - Obesity and Overweight, per our editorial policy and methodology.

Updates

Updated: July 2026. Parameters are verified periodically against the cited sources.

Privacy

Calculations run 100% in your browser. We do not store or transmit your data.

Limitations

Indicative results. For critical decisions, consult a professional.

📌 How to cite this calculator

Rodríguez, M. (2026). BMI Calculator (Body Mass Index). Hacé Cuentas. https://hacecuentas.com/en/bmi-calculator

Content licensed under CC-BY 4.0 — reuse it citing the source with a link to Hacé Cuentas.

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