BMI Calculator

Check Your Body Mass Index Instantly

Curious whether your weight falls within a healthy range for your height? Our free BMI calculator gives you an instant Body Mass Index score along with a clear breakdown of what it means for you. Simply enter your height, weight, gender, and age, and get your BMI, weight category, and personalized healthy weight range in seconds — no sign-up required.

BMI (Body Mass Index) is one of the most widely used screening tools by doctors and health professionals worldwide to assess whether a person's weight is likely to be putting their health at risk. While it isn't a perfect measure — it doesn't account for muscle mass, bone density, or body composition — it remains a useful, quick starting point for understanding your general weight category and tracking changes over time.

Enter your details below to calculate your BMI and see exactly where you stand.

BMI is a general screening tool and does not directly measure body fat or account for muscle mass. Please consult your doctor for a full health assessment.

How Is BMI Calculated?

BMI is calculated using a simple formula based on your height and weight:

• Metric formula: BMI = weight (kg) ÷ height (m)²
• Imperial formula: BMI = 703 × weight (lbs) ÷ height (in)²

For example, someone who is 5'8" (173 cm) and weighs 154 lbs (70 kg) has a BMI of approximately 23.4 — placing them in the "Normal weight" category.

Our calculator handles this math instantly and also converts automatically between Imperial and Metric units, so you don't need to do any manual conversions.

Understanding Your BMI Results

Once you calculate your BMI, you'll fall into one of the following standard categories used by health organizations worldwide:

• Underweight – BMI below 18.5
• Normal weight – BMI between 18.5 and 24.9
• Overweight – BMI between 25 and 29.9
• Obese (Class I, II, III) – BMI of 30 and above

Alongside your score, our calculator shows you a healthy weight range for your exact height, so you know not just your category, but roughly how many pounds or kilos you may need to lose or gain to move into the normal range if applicable.

Is BMI an Accurate Measure of Health?

BMI is a useful starting point, but it has well-known limitations worth understanding:

• It doesn't distinguish between muscle and fat. A muscular athlete can register as "overweight" or "obese" on the BMI scale despite having very low body fat, because muscle weighs more than fat by volume.
• It doesn't account for fat distribution. Two people with the same BMI can have very different health risks depending on where they carry weight (e.g., visceral fat around the abdomen carries higher health risks than fat elsewhere).
• It's a population-level tool. BMI was originally designed for tracking trends across large populations, not for diagnosing an individual's health status.

For this reason, BMI is best used as one data point among several — alongside measurements like waist circumference, body fat percentage, and how you look and feel — rather than a standalone verdict on your health.

How to Use Your BMI Result

If you're in the "Normal weight" range: Your current weight is generally considered healthy for your height. Use this as a baseline and focus on maintaining it through consistent training and balanced nutrition.

If you're in the "Underweight" range: You may benefit from a structured calorie surplus to build healthy weight, ideally paired with resistance training to build muscle rather than just body fat. Try our Calorie Calculator to find your daily calorie target for healthy weight gain.

If you're in the "Overweight" or "Obese" range: A moderate, sustainable calorie deficit combined with regular activity is generally the safest path toward a healthier BMI. Use our Calorie Calculator to calculate a personalized deficit based on your activity level and goals.

Whatever category you fall into, small consistent changes — not drastic ones — tend to produce the most sustainable long-term results.

BMI Categories by Age and Gender

While the standard BMI scale applies broadly to adults, it's worth noting that BMI interpretation can shift slightly with age and differs between men and women due to natural differences in body composition and muscle mass. Older adults, for instance, may carry a slightly higher BMI without the same health risk as a younger adult at the same score, since some muscle loss with age is normal. Our calculator factors in your gender for a more tailored result, and we recommend discussing your specific results with a doctor if you fall outside the normal range.

Frequently Asked Questions

What is a healthy BMI? A BMI between 18.5 and 24.9 is generally considered within the healthy or "normal weight" range for most adults.

Is BMI accurate for athletes or muscular people? Not always. Because BMI doesn't distinguish between muscle and fat, athletes and highly muscular individuals often score as "overweight" or "obese" despite having low body fat. Body fat percentage is a more accurate measure in these cases.

How often should I check my BMI? There's no need to check daily. Recalculating every few weeks, or whenever your weight changes noticeably, is enough to track meaningful trends over time.

Does BMI apply the same way to men and women? The BMI formula itself is the same for both genders, but body composition naturally differs between men and women, which is why our calculator factors in gender to give you more relevant context alongside your score.

What should I do if my BMI is outside the normal range? Use it as a starting point, not a diagnosis. Pair your BMI result with our Calorie Calculator to set an appropriate calorie target, and consult a doctor for a full health assessment, especially if your BMI falls in the underweight or obese categories.

Can children use this BMI calculator? No. BMI calculations for children and teens use different, age- and gender-specific percentile charts. This calculator is designed for adults only (typically ages 18+).

BMI is a general screening tool and does not directly measure body fat percentage, muscle mass, or overall health. Please consult your doctor or a qualified healthcare professional for a complete and personalized health assessment.