❤️ Health
BMI Calculator
Work out your Body Mass Index in kilograms and centimetres or pounds and feet, see which category you fall into and what a healthy weight range would be. Press Calculate.
Understanding your BMI
Body Mass Index divides weight by the square of height, so a taller person is allowed more weight for the same score. It is a fast screening tool, not a diagnosis: it cannot tell muscle from fat, which is why athletes often score "overweight" while carrying very little body fat.
| BMI | Category |
|---|---|
| Below 16 | Severe thinness |
| 16 – 18.4 | Underweight |
| 18.5 – 24.9 | Normal weight |
| 25 – 29.9 | Overweight |
| 30 – 34.9 | Obese class I |
| 35 – 39.9 | Obese class II |
| 40 and above | Obese class III |
Worked example
For someone weighing 70 kg at a height of 1.75 m: BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625, which is 22.9 — comfortably inside the healthy range. Switching to imperial, 154 lb at 5 ft 9 in gives the same figure.
Everyday uses
- A quick, low-cost screening measure
- Tracking direction of travel rather than a single reading
- Understanding the clinical weight categories
- Starting a conversation with a health professional
- Comparing your figure with population ranges
Frequently asked questions
More worked examples
- 70 kg at 1.75 m gives a BMI of 22.9 — comfortably healthy.
- 90 kg at the same height gives 29.4, just below the obese threshold.
- 110 kg at 1.75 m gives 35.9, which falls in obese class I.
- 55 kg at 1.75 m gives 18.0, just under the healthy lower limit of 18.5.
Healthy weight range by height
| Height | BMI 18.5–24.9 |
|---|---|
| 1.60 m | 47.4 – 63.7 kg |
| 1.70 m | 53.5 – 72.0 kg |
| 1.75 m | 56.7 – 76.3 kg |
| 1.80 m | 59.9 – 80.7 kg |
| 5 ft 6 in | 114.6 – 154.3 lb |
| 5 ft 9 in | 125.3 – 168.6 lb |
Common mistakes to avoid
- Treating a single reading as a diagnosis. BMI is a screening tool, not a clinical assessment.
- Applying it to athletes. Muscle is denser than fat, so lean, muscular people frequently score as overweight.
- Using adult thresholds for children, who need age- and sex-specific percentile charts.
- Ignoring ethnicity-specific guidance. Some health bodies use a lower overweight threshold for South Asian populations.
Further questions
Sources and limits
This calculator uses the standard Quetelet index — weight in kilograms divided by height in metres squared — and the World Health Organization adult cut-offs shown above. BMI is a population screening measure, not a description of an individual: it cannot separate fat from muscle or show where fat is stored.
- World Health Organization — Obesity and overweight
- NHS — Obesity: BMI and health risk
- Centers for Disease Control and Prevention — About adult BMI
Healthy weight range by height
The range below is the weight that puts a person at BMI 18.5 to 24.9 for each height. It is a population band, not a target: waist circumference and body composition describe risk better than the band alone.
| Height | BMI 18.5-24.9 | In pounds | Upper limit in pounds |
|---|---|---|---|
| 150 cm | 42-56 kg | 92-124 lb | 124 lb |
| 155 cm | 44-60 kg | 98-132 lb | 132 lb |
| 160 cm | 47-64 kg | 104-141 lb | 141 lb |
| 165 cm | 50-68 kg | 111-149 lb | 149 lb |
| 170 cm | 53-72 kg | 118-159 lb | 159 lb |
| 175 cm | 57-76 kg | 125-168 lb | 168 lb |
| 180 cm | 60-81 kg | 132-178 lb | 178 lb |
| 185 cm | 63-85 kg | 140-188 lb | 188 lb |
| 190 cm | 67-90 kg | 147-198 lb | 198 lb |
| 195 cm | 70-95 kg | 155-209 lb | 209 lb |
BMI is weight divided by height squared, so the healthy range widens with height rather than shifting evenly. At 150 cm the band spans about 14 kg; at 195 cm it spans about 24 kg.