How BMI Calculator works
Body mass index is weight in kilograms divided by height in metres squared. Enter your height and weight and this calculator returns the BMI to one decimal place, the World Health Organization category it falls in, and the range of weights that give a BMI of 18.5 to 24.9 at your height. Someone 170 cm tall weighing 70 kg has a BMI of 24.2, which is in the healthy band, and a healthy range of 53.5 to 72 kg. Switch Units to imperial to enter feet, inches and pounds and see the range in pounds. BMI is a screening measure for adults and does not diagnose anything on its own.
Healthy weight range by height in cm and kg
The Healthy range the calculator returns for each height: the weights that give a BMI of 18.5 to 24.9.
| Height | Lowest healthy weight | Highest healthy weight |
|---|---|---|
| 145 cm | 38.9 kg | 52.4 kg |
| 150 cm | 41.6 kg | 56 kg |
| 155 cm | 44.4 kg | 59.8 kg |
| 160 cm | 47.4 kg | 63.7 kg |
| 165 cm | 50.4 kg | 67.8 kg |
| 170 cm | 53.5 kg | 72 kg |
| 175 cm | 56.7 kg | 76.3 kg |
| 180 cm | 59.9 kg | 80.7 kg |
| 185 cm | 63.3 kg | 85.2 kg |
| 190 cm | 66.8 kg | 89.9 kg |
| 195 cm | 70.3 kg | 94.7 kg |
| 200 cm | 74 kg | 99.6 kg |
For adults. The span is wide on purpose: at 175 cm there are almost 20 kg between the bottom and the top of the healthy band.
Healthy weight range by height in feet, inches and pounds
The same range with Units set to imperial.
| Height | Lowest healthy weight | Highest healthy weight |
|---|---|---|
| 4 ft 10 in | 88.5 lb | 119.1 lb |
| 5 ft 0 in | 94.7 lb | 127.5 lb |
| 5 ft 1 in | 97.9 lb | 131.8 lb |
| 5 ft 2 in | 101.1 lb | 136.1 lb |
| 5 ft 3 in | 104.4 lb | 140.6 lb |
| 5 ft 4 in | 107.8 lb | 145.1 lb |
| 5 ft 5 in | 111.2 lb | 149.6 lb |
| 5 ft 6 in | 114.6 lb | 154.3 lb |
| 5 ft 7 in | 118.1 lb | 159 lb |
| 5 ft 8 in | 121.7 lb | 163.8 lb |
| 5 ft 9 in | 125.3 lb | 168.6 lb |
| 5 ft 10 in | 128.9 lb | 173.5 lb |
| 5 ft 11 in | 132.6 lb | 178.5 lb |
| 6 ft 0 in | 136.4 lb | 183.6 lb |
| 6 ft 1 in | 140.2 lb | 188.7 lb |
| 6 ft 2 in | 144.1 lb | 193.9 lb |
| 6 ft 3 in | 148 lb | 199.2 lb |
| 6 ft 4 in | 152 lb | 204.6 lb |
BMI categories for adults
| BMI | WHO category | Shown by this calculator as |
|---|---|---|
| Below 18.5 | Underweight | Underweight |
| 18.5 to 24.9 | Normal weight | Healthy weight |
| 25.0 to 29.9 | Overweight (pre-obesity) | Overweight |
| 30.0 to 34.9 | Obesity class I | Obese |
| 35.0 to 39.9 | Obesity class II | Obese |
| 40.0 and above | Obesity class III | Obese |
The calculator reports a single Obese band from 30.0 upward and does not split it into classes. These cut-offs apply to adults only; children and teenagers are assessed with age and sex percentile charts.
Worked BMI examples in metric and imperial
Default metric example
Units metric, Height 170 cm, Weight 70 kg
BMI 24.2, category Healthy weight, healthy range 53.5 kg to 72 kg.
Above the healthy band
Units metric, Height 180 cm, Weight 95 kg
BMI 29.3, category Overweight, healthy range 59.9 kg to 80.7 kg.
The top of the healthy range is 14.3 kg below the current weight.
Below the healthy band
Units metric, Height 165 cm, Weight 48 kg
BMI 17.6, category Underweight, healthy range 50.4 kg to 67.8 kg.
Imperial units
Units imperial, Height 5 feet 10 inches, Weight 160 lb
BMI 23, category Healthy weight, healthy range 128.9 lb to 173.5 lb.
BMI of 30 or more
Units imperial, Height 5 feet 4 inches, Weight 180 lb
BMI 30.9, category Obese, healthy range 107.8 lb to 145.1 lb.
BMI formula and how the healthy range is reversed from it
BMI = weight (kg) / height (m) squared. Imperial: BMI = weight (lb) x 703 / height (in) squared. Lowest healthy weight = 18.5 x height (m) squared. Highest healthy weight = 24.9 x height (m) squared.
For 70 kg at 1.70 m, height squared is 2.89 and 70 / 2.89 = 24.2. Reversing the formula at the same height gives 18.5 x 2.89 = 53.5 kg and 24.9 x 2.89 = 72 kg, the two ends of the healthy range. In imperial mode the calculator does not use the 703 shortcut. It converts feet and inches to metres at 0.0254 m per inch and pounds to kilograms at 0.45359237 kg per pound, runs the metric formula, and converts the range back to pounds. The category is decided on the unrounded BMI, so a result that displays as 25 can still be labelled Healthy weight when the exact value is just under 25. The top of the Healthy range is worked out at 24.9, so a weight that gives a BMI between 24.9 and 25 is labelled Healthy weight while sitting a little above the range shown.
When BMI is a poor guide
BMI cannot tell muscle from fat. A muscular person can land in the overweight or obese band with little body fat, and an older adult who has lost muscle can sit in the healthy band while carrying a lot of fat around the waist.
Risk also varies between populations. A World Health Organization expert consultation in 2004 found that health risks rise at a lower BMI in many Asian populations and suggested 23 and 27.5 as additional points for public health action, alongside the standard 25 and 30. This calculator uses the standard cut-offs only.
The adult categories do not apply to children and teenagers, who need age and sex percentile charts, or during pregnancy. Waist measurement adds information that BMI lacks; a common rule of thumb is to keep the waist below half of your height. Use the number here as a prompt for a conversation with a doctor or nurse, not as a verdict.
How to use it
- 1
Choose Units: Metric (cm / kg) or Imperial (ft·in / lb).
- 2
For metric, fill in Height (cm) and Weight (kg). For imperial, fill in Height (feet), Height (inches) and Weight (lb).
- 3
Read BMI and Category in the result panel.
- 4
Read Healthy range for the lowest and highest weight that fall in the 18.5 to 24.9 band at your height.
- 5
Check the BMI categories (WHO) table, where a tick marks your current band.