BMI Calculator
Body mass index, its category, and the healthy weight range for your height.
Last updated
Your details
Result
- Your BMI
- 22.9
- Healthy weight for your height
- 56.7 – 76.3 kg
- Status
- Within the healthy range
- BMI thresholds
- Under 18.5 · 18.5–24.9 · 25–29.9 · 30+
Normal weight
Underweight · Normal · Overweight · Obese
Formula — written step by step
For 70 kg at 175 cm…
BMI = weight ÷ height²
height = 175 cm = 1.75 m
BMI = 70 ÷ 1.75²
BMI = 70 ÷ 3.0625
BMI = 22.9
Weight in kilograms, height in metres — not centimetres. Squaring 175 instead of 1.75 is the single most common mistake, and it produces a BMI ten thousand times too small.
A worked example
BMI for 70 kg at 175 cm
- Weight
- 70 kg
- Height
- 175 cm
- BMI = weight (kg) ÷ height (m)²
- BMI = 70 ÷ 1.75²
- BMI = 70 ÷ 3.0625
BMI = 22.9 — within the normal range
The healthy band for this height runs from 56.7 kg to 76.3 kg, which is what the 18.5 and 24.9 thresholds work out to once multiplied back by 1.75².
How to use this calculator
- Enter your weight in kilograms and your height in centimetres.
- The BMI figure appears immediately, with its category underneath.
- The healthy weight range shown is the 18.5 to 24.9 band converted back into kilograms for your height — usually the more actionable number.
- Treat the result as a screening signal, not a diagnosis. Waist circumference and body-fat percentage tell you what BMI cannot.
What BMI measures — and what it misses
BMI is weight in kilograms divided by height in metres squared. It was designed in the 1830s to describe populations, not to diagnose individuals, and it remains a screening signal rather than a verdict.
It cannot distinguish muscle from fat. A trained athlete frequently lands in the "overweight" band with very low body fat, while someone sedentary can sit in the "normal" band carrying substantial visceral fat. Waist circumference and body-fat percentage add the detail BMI omits.
Where the thresholds come from
The cutoffs at 18.5, 25 and 30 come from WHO analysis of mortality and disease risk in largely European-descent populations. Several health bodies use lower thresholds for people of South and East Asian descent, where metabolic risk rises at a lower BMI — often 23 for overweight and 27.5 for obesity.
BMI is also unreliable for children, pregnant people, and anyone over roughly 65, where height loss and body-composition changes distort the ratio.
Formula & methodology
What this calculator assumes
- The 18.5 / 25 / 30 thresholds are the WHO adult classification and apply to adults aged roughly 20–65.
- BMI cannot distinguish muscle from fat, and is unreliable for athletes, pregnant people, children and older adults.
- Several health bodies apply lower thresholds for people of South and East Asian descent, where metabolic risk rises at a lower BMI.
Sources
- World Health Organization. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894, 2000.
- WHO Expert Consultation. Appropriate body-mass index for Asian populations. The Lancet, 2004;363(9403):157–163.
BMI categories, and what they mean at 175 cm
| Category | BMI | Weight at 175 cm |
|---|---|---|
| Underweight | Under 18.5 | Under 56.7 kg |
| Normal | 18.5 – 24.9 | 56.7 – 76.3 kg |
| Overweight | 25 – 29.9 | 76.6 – 91.6 kg |
| Obese | 30 and over | 91.9 kg and over |
These thresholds are the WHO cut-offs for adults of European descent. Several health authorities apply lower thresholds for people of South and East Asian descent, where cardiometabolic risk rises at a lower BMI.
Frequently asked questions
Is BMI accurate for muscular people?
No. Muscle is denser than fat, so athletes routinely register as overweight despite low body fat. Use body-fat percentage instead.
What BMI should I aim for?
There is no single ideal. The 18.5–24.9 band is associated with the lowest average risk across populations, but individual health depends far more on activity, diet, sleep and blood markers than on a single ratio.