BMI Calculator: Check Your Body Mass Index Free and Privately
A BMI calculator turns height and weight into a Body Mass Index, a number used to screen adults for weight-related health risk. Enter your height and weight above in metric or imperial units and this free BMI calculator shows your BMI to one decimal place, its WHO or Asian (Asia-Pacific) category, the healthy weight range for your height and the weight change that reaches its edge. It is a screening figure for adults aged 18 and over, not a diagnosis.
The calculation runs in your browser and nothing is uploaded; you can check the Network tab in DevTools. Only the Save to history button stores anything, in your browser's local storage.
The BMI formula
Metric: BMI = weight (kg) ÷ height (m)². Imperial: BMI = 703 × weight (lb) ÷ height (in)². At 70 kg and 175 cm, BMI = 70 ÷ 1.75² = 22.9. The calculator converts with exact factors (1 lb = 0.45359237 kg, 1 in = 0.0254 m), rounds to one decimal and picks the category from the rounded value, so 24.96 shows as 25.0 and counts as Overweight.
BMI categories as of October 2026
| Category | WHO standard | Asia-Pacific |
|---|---|---|
| Underweight | Under 18.5 | Under 18.5 |
| Normal | 18.5 to 24.9 | 18.5 to 22.9 |
| Overweight | 25 to 29.9 | 23 to 24.9 (at risk) |
| Obese Class I | 30 to 34.9 | 25 to 29.9 |
| Obese Class II | 35 to 39.9 | 30 and above |
| Obese Class III | 40 and above | included in Class II |
Sources: the WHO adult classification and the WHO Western Pacific Region report The Asia-Pacific perspective: redefining obesity and its treatment (2000). Countries may set their own cut-offs.
BMI Calculator Table of Use: Inputs and Results
| Situation | You enter | You get |
|---|---|---|
| Metric check | 175 cm, 70 kg | BMI 22.9, Normal; healthy range 56.7 to 76.3 kg; 67.4 kg at BMI 22 |
| Imperial check | 5 ft 9 in, 154 lbs | BMI 22.7, Normal; healthy range 125.3 to 168.6 lbs |
| Above the normal range | 180 cm, 100 kg | BMI 30.9, Obese Class I; about 19.3 kg less reaches 24.9 |
| Below the normal range | 165 cm, 45 kg | BMI 16.5, Underweight; about 5.4 kg more reaches 18.5 |
| One body, two scales | 160 cm, 70 kg | BMI 27.3: Overweight (WHO) or Obese Class I (Asia-Pacific) |
BMI Calculator Features
- Metric or imperial: centimetres and kilograms, or feet, inches and pounds. Switching units converts the values already typed. A decimal comma such as 45,5 is accepted.
- Two scales: WHO standard and Asian (Asia-Pacific), each with its own category cards and a colour bar.
- Healthy weight range: the weights for your height that give BMI 18.5 to 24.9 (18.5 to 22.9 on the Asian scale), plus the weight at BMI 22 and the weight change that reaches the nearest edge when you are outside it.
- Mix-up checks: heights outside 50 to 275 cm and weights outside 10 to 650 kg (23 to 1,433 lbs) are refused, and 1.75 in the cm box gets a hint to use centimetres.
- Copy and history: Copy gives a text summary; Save to history keeps up to 50 readings in this browser, shows the latest 10 and charts the trend.
It asks for no age or sex and gives no body-fat figure; for that, use the Body Fat Calculator.
How to Use the BMI Calculator
- Choose Metric (kg/cm) or Imperial (lbs/ft).
- Type your height: Height (cm), or whole feet plus inches.
- Type your Weight in the unit shown.
- Pick WHO standard or Asian (Asia-Pacific) under BMI classification scale.
- Read Your Results: BMI, category, healthy weight range and weight at BMI 22. Press Copy or Save to history if needed.
Who Can Use the BMI Calculator
Adults wanting a quick screening number, people tracking weight over months and students learning how BMI works can use it. It is not for children, teenagers or pregnancy; discuss any result with a doctor.
Related tools: the Ideal Weight Calculator uses published height formulas, the Calorie Calculator estimates daily energy needs, and the Age Calculator gives your exact age. Expectant parents can use the Pregnancy Due Date Calculator instead. To change measurements first, try the Weight Converter, the Length Converter or the Unit Converter, and the Percentage Calculator gives a weight change as a percentage.
BMI Calculator FAQs
What is a healthy BMI for an adult?
As of October 2026, the WHO classes an adult BMI of 18.5 to 24.9 as normal weight, under 18.5 as underweight, 25 to 29.9 as overweight and 30 or more as obese. The WHO Western Pacific Region suggests lower cut-offs for Asian adults: 18.5 to 22.9 is normal and 23 or more is overweight.
How do I calculate my BMI from height and weight?
Divide your weight in kilograms by your height in metres squared: 70 kg at 175 cm is 70 ÷ (1.75 × 1.75) = 22.9. In imperial units, multiply your weight in pounds by 703 and divide by your height in inches squared. The calculator does this for you with exact unit factors; 703 is a rounded shortcut for 703.07.
How do I calculate BMI in pounds, feet and inches?
Press "Imperial (lbs/ft)", type whole feet in the feet box, the remaining inches in the inches box and your weight in pounds. Someone 5 ft 9 in tall weighing 154 lbs has a BMI of 22.7, Normal on the WHO scale. Switching units converts the numbers already typed.
How much weight do I need to lose to reach a healthy BMI?
When your BMI is above the normal range, the results panel shows the weight difference to the top of that range. At 180 cm and 100 kg, BMI is 30.9 and about 19.3 kg less would reach 24.9. This is arithmetic from BMI alone, not medical advice, so agree any weight goal with a doctor.
Why does my BMI seem wrong for my body?
BMI uses only height and weight, so it cannot tell muscle from fat or show where fat is stored. Muscular people can be classed as overweight with little body fat, while older adults who have lost muscle can have a normal BMI and high body fat. A waist measurement or body fat estimate adds detail.
Should I use the WHO or the Asian BMI scale?
If you are of East, South or Southeast Asian descent, the Asian (Asia-Pacific) scale is usually the better guide, because studies show higher diabetes and heart-disease risk at lower BMIs in these groups. A 160 cm adult weighing 70 kg is Overweight on the WHO scale but Obese Class I on the Asia-Pacific one.
Can I use this BMI calculator for children or during pregnancy?
No. Children and teenagers need BMI-for-age growth charts, and weight gain in pregnancy is assessed differently. This calculator asks for no age or sex and applies fixed adult cut-offs, so use it only if you are 18 or over and not pregnant.
Where is my BMI history saved, and is anything uploaded?
Nothing is uploaded. If you press "Save to history", the date, BMI, height, weight and unit are stored in your browser's local storage on this device, up to 50 records. They stay in this browser only and do not appear on other devices; clearing browser data deletes them, and you can delete single records or press "Clear all".