BMI Calculator: Work Out Your BMI and Healthy Weight Range

title: "BMI Calculator: Work Out Your BMI and Healthy Weight Range" description: "Free BMI calculator in kg/cm or lb/ft, with the WHO categories, your healthy weight range for your height, and what BMI can and can't tell you." publishedAt: "2026-10-05" updatedAt: "2026-10-05" category: "Weight loss" tags: ["BMI calculator", "body mass index", "healthy weight range", "BMI chart", "what is a healthy BMI"] keyTakeaways:

• "BMI is your weight in kilograms divided by your height in metres squared. In pounds and inches, it's weight × 703 ÷ height²."
• "For adults, the WHO categories are: under 18.5 underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, and 30 or more obesity."
• "For people of Asian descent, the WHO suggests acting at lower points: BMI 23 for increased risk and 27.5 for high risk."
• "BMI can't tell muscle from fat. Pair it with your waist measurement: a waist under half your height is the NICE guideline target."
• "BMI is a screening number, not a diagnosis. Children, pregnant people and very muscular adults need other measures." faq:
• question: "How do I calculate my BMI?" answer: "Divide your weight in kilograms by your height in metres squared. For example, 70 kg ÷ (1.70 m × 1.70 m) = 24.2. In imperial units, multiply your weight in pounds by 703 and divide by your height in inches squared: 154 lb × 703 ÷ (67 in × 67 in) = 24.1."
• question: "What is a healthy BMI?" answer: "For most adults, 18.5 to 24.9. The WHO uses 25 to 29.9 for overweight and 30 or more for obesity. For people of Asian descent, the WHO suggests that health risk starts rising from about 23."
• question: "What is a healthy weight for my height?" answer: "Multiply your height in metres squared by 18.5 and by 24.9. For 1.70 m that gives 53 to 72 kg. The calculator above works this out for your height in kg or lb."
• question: "Is BMI accurate?" answer: "It is a quick screening tool, not a body-fat measurement. It overestimates fat in very muscular people and can underestimate it in older adults who have lost muscle. Measuring your waist alongside it gives a better picture of health risk."
• question: "Is BMI different for women and men?" answer: "The adult categories are the same for both. Women usually carry more body fat than men at the same BMI, which is one reason BMI works only as a rough guide for individuals."

Enter your height and weight below and the calculator gives your BMI, its category and the healthy weight range for your height.

The 30-second answer

BMI = weight (kg) ÷ height (m)². A BMI from 18.5 to 24.9 is the healthy range for most adults. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or more is obesity (WHO). Use the calculator for your own number and healthy weight range:

BMI categories for adults

The lower cut-offs for Asian populations come from a WHO expert consultation published in The Lancet. It found that type 2 diabetes and heart disease risk rise at lower BMIs in many Asian populations. Several countries, including India and Singapore, use these lower points in their own guidance.

How to calculate BMI by hand

Metric: weight in kg ÷ (height in m × height in m).

• Example: 82 kg and 1.78 m → 82 ÷ (1.78 × 1.78) = 82 ÷ 3.17 = 25.9.

Imperial: weight in lb × 703 ÷ (height in inches × height in inches).

• Example: 180 lb and 5 ft 10 in (70 in) → 180 × 703 ÷ 4,900 = 25.8.

To get your healthy weight range, run it backwards: multiply your height in metres squared by 18.5 for the bottom of the range and by 24.9 for the top.

Healthy weight range by height

What BMI can't tell you

BMI is useful because it needs only a tape measure and a scale. It has three blind spots:

1. Muscle weighs the same as fat on a scale. A muscular person can have a BMI over 25 with little body fat.
2. It ignores where fat sits. Fat around the waist carries more health risk than fat on the hips. The UK's NICE guideline asks clinicians to measure waist-to-height ratio alongside BMI for adults with a BMI under 35, and to advise keeping your waist under half your height.
3. It shifts with age and ethnicity. Older adults often lose muscle, so the same BMI can mean more fat. Risk also starts at lower BMIs in some ethnic groups, as the table above shows.

BMI is not designed for children, teenagers or pregnancy. Children are assessed with age- and sex-specific growth charts.

What to do with your number

• BMI 18.5 to 24.9: focus on keeping your waist under half your height and on how you eat, not on a new weight target.
• BMI 25 or more: losing 5–10% of your body weight improves blood pressure, blood sugar and cholesterol for most people (NHLBI). Work out your calorie target with our calorie calculator or read how many calories to eat to lose weight.
• BMI under 18.5: talk to a doctor if you have lost weight without trying. If you're trying to gain, see our healthy weight gain guide.

How Callie uses BMI

Callie is our app. When you pick a diet (keto, intermittent fasting, a calorie cut, balanced or custom), Callie: AI Calorie Tracker uses your BMI, weight, fitness level and allergies to suggest the day's meals and exercises. It then re-tunes your calorie target every two weeks from your actual weight trend, so a starting estimate that's a little off doesn't stay off. It is not a medical device.

Sources

1. World Health Organization. Obesity and overweight fact sheet. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
2. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. The Lancet, 2004;363:157–163. https://pubmed.ncbi.nlm.nih.gov/14726171/
3. NICE. Overweight and obesity management (NG246), January 2025. https://www.nice.org.uk/guidance/ng246/chapter/Identifying-and-assessing-overweight-obesity-and-central-adiposity
4. National Heart, Lung, and Blood Institute. Assessing your weight and health risk. https://www.nhlbi.nih.gov/health/educational/lose_wt/risk.htm
5. CDC. Adult BMI calculation formulas. https://www.cdc.gov/bmi/adult-calculator/index.html