BMI · Laskuri

BMI-laskuri

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BMI-laskuri

Yksiköt

Paino

Pituus

Ikä

Sukupuoli

BMI-arvo

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16 18.5 25 30 35 40+

Suositeltu paino (BMI 18.5–24.9)

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Rasvaprosentti (arvio)

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Terveellinen paino

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Painonpito tasapainoon

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Ikä

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BMI-luokitukset (WHO)

Tila	BMI-alue
Alipainoinen	< 18.5
Normipainoinen	18.5 – 24.9
Ylipainoinen	25.0 – 29.9
Lihava (I asteen)	30.0 – 34.9
Lihava (II–III asteen)	≥ 35.0

BMI Guide

What is BMI — and what does your number actually mean?

Body Mass Index (BMI) is a numerical value calculated from a person's weight and height. It was developed in the 1830s by Belgian mathematician Adolphe Quetelet as a population-level screening tool, and was later adopted by the World Health Organization (WHO) as a simple proxy for assessing whether an individual's weight falls into a healthy range relative to their stature.

BMI does not directly measure body fat — it is an indirect estimate. Its popularity stems from its simplicity: all you need is a scale and a tape measure. Despite well-known limitations (discussed below), BMI remains the most widely used clinical screening tool for weight classification worldwide, and a BMI outside the normal range is associated with measurably higher risks for a range of chronic diseases.

The BMI Formula

The mathematics behind the calculation

Metric (kg / cm)

BMI = weight (kg) ÷ height (m)²

Height in metres — divide cm value by 100 first

Imperial (lbs / inches)

BMI = (weight (lbs) ÷ height (in)²) × 703

The factor 703 converts lb/in² to kg/m²

Worked Example

A person who weighs 75 kg and is 175 cm (1.75 m) tall has a BMI of:

BMI = 75 ÷ (1.75)² = 75 ÷ 3.0625 ≈ 24.49

This falls in the Normal weight range (18.5 – 24.9)

Body Fat Percentage Estimate (Deurenberg Formula)

This calculator also estimates body fat percentage using the Deurenberg et al. (1991) regression formula, which combines BMI, age, and sex:

Body Fat % = (1.2 × BMI) + (0.23 × Age) − 16.2 [male]

Body Fat % = (1.7 × BMI) + (0.2 × Age) − 54 [female]

This is an estimate with a standard error of approximately ±3–4 percentage points. For precise body composition analysis, methods such as DEXA scanning, hydrostatic weighing, or bioelectrical impedance are more accurate.

WHO BMI Classification — In Detail

What each category means for health risk

Underweight — BMI below 18.5

Being underweight can indicate malnutrition, an eating disorder, or an underlying medical condition. Health risks include weakened immune function, reduced bone density (osteoporosis), anaemia, and, in severe cases, organ failure. Women who are underweight may experience fertility issues. Gradual, supervised weight gain through increased caloric intake and strength training is generally recommended.

Normal weight — BMI 18.5 to 24.9

This range is associated with the lowest risk of weight-related chronic disease in population studies. However, a BMI in the normal range does not guarantee good health — physical activity level, diet quality, sleep, and other lifestyle factors are equally important. Maintaining this range over a lifetime through balanced nutrition and regular exercise is a widely supported health goal.

Overweight — BMI 25.0 to 29.9

A BMI in this range is associated with a moderately elevated risk of type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers. Many people in this range are metabolically healthy, particularly if they are physically active. Even modest weight loss of 5–10 % of body weight has been shown to meaningfully reduce risk factors. Diet quality improvements and increased aerobic activity are first-line interventions.

Obese Class I — BMI 30.0 to 34.9

Class I obesity carries a substantially elevated risk of metabolic syndrome, sleep apnoea, joint problems, and cardiovascular disease. Clinical guidelines recommend structured lifestyle interventions including medical nutrition therapy, supervised exercise programmes, and — where appropriate — pharmacological support. Regular monitoring of blood pressure, blood glucose, and cholesterol is advised.

Obese Class II–III — BMI 35.0 and above

Severe obesity (BMI ≥ 35) is associated with significantly reduced life expectancy and a high burden of co-morbidities. Comprehensive medical management involving a multidisciplinary team is strongly recommended. In eligible patients, bariatric surgery has been shown to produce sustained weight loss and resolution of metabolic conditions such as type 2 diabetes. Early intervention is more effective than delayed treatment.

Limitations of BMI

Why BMI is a useful starting point but not the whole picture

🏋️ Athletes and muscle mass

Muscle is denser than fat, so athletes and highly active individuals often have a BMI in the overweight or obese range despite very low body fat and excellent cardiovascular fitness. BMI cannot distinguish between fat mass and lean mass.

👴 Age-related changes

As people age, they typically lose muscle mass and gain body fat even if total weight stays stable. An older adult with a "normal" BMI may carry a disproportionate amount of visceral fat. Conversely, a higher BMI in the elderly is sometimes associated with better outcomes — the so-called "obesity paradox."

🌍 Ethnic and racial differences

Research indicates that people of Asian descent tend to have higher body fat percentages at lower BMI values compared to people of European descent. The WHO recommends using lower BMI cut-offs (≥ 23 for overweight, ≥ 27.5 for obesity) for Asian populations.

🤰 Pregnancy

BMI is not applicable during pregnancy. Weight gain during pregnancy is expected and necessary. Healthcare providers use separate gestational weight gain guidelines based on pre-pregnancy BMI rather than tracking BMI itself during the pregnancy.

👶 Children and adolescents

For individuals under 18, BMI is interpreted differently. Instead of fixed thresholds, paediatric BMI is plotted on age- and sex-specific growth charts, and results are expressed as percentiles. The standard adult BMI cut-offs do not apply.

📏 Body shape and fat distribution

Where fat is stored matters as much as how much fat you carry. Visceral fat (around internal organs) is more metabolically harmful than subcutaneous fat. Waist circumference and waist-to-height ratio are complementary measures that better capture this risk dimension.

Despite these limitations, BMI remains a valuable and cost-free first screening step. When used alongside waist circumference, blood pressure, fasting glucose, and cholesterol measurements, it contributes meaningfully to a holistic picture of metabolic health. Always discuss your results with a qualified healthcare professional.

Evidence-Based Strategies for a Healthy Weight

Approaches supported by clinical research

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Prioritise whole foods and dietary fibre

Diets rich in vegetables, legumes, whole grains, and lean protein support healthy weight management by improving satiety signalling. High fibre intake slows gastric emptying and moderates blood glucose spikes. Large-scale trials consistently show that dietary patterns — rather than single nutrients — drive long-term outcomes. The Mediterranean and DASH dietary patterns have the strongest evidence base.

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Combine aerobic exercise with resistance training

WHO guidelines recommend at least 150–300 minutes of moderate-intensity aerobic activity per week, plus muscle-strengthening activities on two or more days. Resistance training is particularly important because it preserves lean muscle mass during caloric restriction, maintaining resting metabolic rate and improving insulin sensitivity. Combining both modalities produces better body composition outcomes than either alone.

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Protect sleep quality and quantity

Sleep deprivation disrupts the hormones that regulate appetite — increasing ghrelin (hunger) and decreasing leptin (satiety). Even one week of sleeping less than six hours per night measurably impairs glucose metabolism. Adults generally need 7–9 hours of quality sleep per night. Poor sleep is an often-overlooked but significant driver of weight gain and metabolic dysfunction.

🧠

Manage stress and emotional eating

Chronic psychological stress elevates cortisol, which promotes fat storage — particularly visceral fat — and increases cravings for calorie-dense foods. Cognitive-behavioural approaches, mindfulness-based eating awareness training, and stress reduction techniques have demonstrated efficacy in supporting healthier food choices and weight management over time.

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Track progress, but measure broadly

Weight on a scale fluctuates daily by 1–3 kg due to hydration, glycogen, and digestive content. Track weekly trends rather than daily readings. Consider complementing BMI with waist circumference, resting heart rate, and fitness benchmarks. Improving fitness and metabolic markers — even without dramatic weight loss — is a meaningful and achievable goal that reduces health risk.

Frequently Asked Questions

Is BMI an accurate measure of health? ▾

At the population level, BMI is a useful epidemiological tool — it correlates reasonably well with body fat percentage and with chronic disease risk across large groups. At the individual level, BMI is a starting point rather than a definitive health verdict. A person with a BMI of 27 who exercises daily, has normal blood pressure and cholesterol, and eats well may be significantly healthier than a sedentary person with a BMI of 23. Always interpret BMI alongside other clinical information.

What is a healthy BMI for women vs. men? ▾

The WHO uses the same BMI thresholds (18.5–24.9 for normal weight) for both sexes. However, women naturally carry a higher percentage of body fat than men at the same BMI — typically 5–8 percentage points more — due to hormonal and reproductive differences. This means the health implications of a given BMI value differ somewhat by sex, which is why this calculator includes a sex variable in the body fat estimate.

How much weight do I need to lose to reach a normal BMI? ▾

The calculator shows the weight difference needed to bring your BMI to the top of the normal range (24.9). To calculate this yourself: multiply 24.9 by your height in metres squared. The result is the maximum weight in kg for a normal BMI. Subtract your current weight to find the difference. A clinically sustainable rate of weight loss is generally 0.5–1 kg per week, achieved through a modest caloric deficit of 500–1000 kcal/day. Rapid weight loss often leads to muscle loss and metabolic adaptation.

Mikä on normaali BMI suomalaisille? (Finnish) ▾

WHO:n mukaan normaali BMI on 18,5–24,9 kaikille aikuisille kansallisuudesta riippumatta. Suomessa käytetään samoja raja-arvoja kuin muuallakin Euroopassa. Suomalaisen aikuisväestön keskimääräinen BMI on viime vuosikymmeninä noussut — Terveyden ja hyvinvoinnin laitoksen (THL) FinTerveys 2017 -tutkimuksen mukaan yli puolella suomalaisista aikuisista BMI ylitti 25. Lihavuuden kustannukset terveydenhuollolle ovat merkittävät, minkä vuoksi painonhallintaa tuetaan aktiivisesti perusterveydenhuollossa.

Каков нормальный ИМТ для взрослых? (Russian) ▾

По классификации ВОЗ нормальный ИМТ для взрослых составляет от 18,5 до 24,9. Значения ниже 18,5 соответствуют дефициту массы тела, 25–29,9 — избыточному весу, а 30 и выше — ожирению различной степени. Для людей азиатского происхождения ВОЗ рекомендует использовать пониженные пороговые значения: избыточный вес диагностируется уже при ИМТ ≥ 23, ожирение — при ≥ 27,5. Для детей и подростков ИМТ интерпретируется по специальным возрастным и половым таблицам роста.

Can I have a healthy BMI but still be at risk? ▾

Yes. The condition sometimes called "normal weight obesity" or "metabolically obese normal weight" (MONW) describes individuals with a BMI in the normal range but with excess body fat — particularly visceral fat — and associated metabolic risk factors such as insulin resistance, elevated triglycerides, and low HDL cholesterol. This is why measuring waist circumference (target: below 88 cm for women, below 102 cm for men) in addition to BMI gives a more complete risk picture. Lifestyle factors like physical inactivity, smoking, and poor diet contribute to metabolic risk independently of BMI.

Ideal Weight Range by Height

Weight range corresponding to a BMI of 18.5 – 24.9 (metric, WHO normal range)

Height (cm)	Min (18.5)	Max (24.9)	Midpoint
155 cm	44.4 kg	59.8 kg	52.1 kg
160 cm	47.4 kg	63.7 kg	55.6 kg
165 cm	50.3 kg	67.7 kg	59.0 kg
170 cm	53.5 kg	71.9 kg	62.7 kg
175 cm	56.7 kg	76.3 kg	66.5 kg
180 cm	59.9 kg	80.7 kg	70.3 kg
185 cm	63.3 kg	85.2 kg	74.3 kg
190 cm	66.8 kg	89.8 kg	78.3 kg

Calculated as weight (kg) = BMI × height (m)². These are population-level reference ranges. Individual ideal weight depends on muscle mass, bone density, age, and other factors. Consult a healthcare professional for personalised guidance.