BMI Calculator
Check your Body Mass Index and see where you stand
This BMI calculator returns your Body Mass Index in seconds, plus the healthy weight range for your height. Enter height in cm or feet/inches and weight in kg or lbs. The formula is the standard kg/m squared used by WHO, NHLBI, CDC, and Health Canada.
What this tool is for: a fast, free screening check. What it is not: a diagnosis, and not the right tool for every body. A 178 cm lifter at 90 kg with 10% body fat will land in the WHO "overweight" band (BMI 28.4). So will a 90 kg sedentary office worker with 32% body fat. Same BMI, completely different metabolic story. The number below the calculator is the starting point of a conversation, not the end of one.
Built and reviewed by Kazi Habib, B.Pharm, MBA, PMP, the pharmacist behind FitFixLife. The calculator code uses the WHO adult categories. The deep dive below covers when those categories work, when they miss (especially for South Asian and East Asian adults whose risk thresholds shift lower), and the tools that work better than BMI when you need a real read on body composition.
How this calculator works
BMI is weight in kilograms divided by height in metres squared. If you enter pounds and feet, the calculator converts internally. Your result lands in one of four standard WHO bands: underweight (under 18.5), normal (18.5 to 24.9), overweight (25.0 to 29.9), or obese (30.0 and up). The healthy weight range we show is the kg or lb range that would put you between BMI 18.5 and 24.9 at your height.
We use the WHO/NHLBI cutoffs as the default because they are what most clinicians, GPs, and Canadian primary care providers reference. The NHLBI BMI categories match these exactly. We do not display Asian-specific thresholds in the gauge by default, but they matter for a large share of our readers (covered below).
When to use this calculator
Use this calculator when you want a fast screening number to track over months as your weight changes, when a clinician asked for your BMI and you do not have a recent reading, when you are calculating eligibility for a program (some Canadian provincial weight-management referrals use BMI cutoffs), or when you want to see the healthy weight range for your height as a target band rather than a single number.
When NOT to use this calculator
BMI breaks down for several groups. If you lift heavily or carry substantial muscle mass, BMI will overcall your category. If you are over 65 with possible sarcopenia, BMI can mask a high body fat percentage hiding under normal scale weight. If you are pregnant, use prenatal weight gain charts from your provider instead. If you are an adult of South Asian, East Asian, Southeast Asian, or Middle Eastern background, the standard WHO cutoffs under-diagnose risk in these populations.
Better tools for those cases: waist circumference (Health Canada flags over 102 cm for men, over 88 cm for women, with lower cutoffs of 90 cm and 80 cm for South Asian and Chinese Canadians); waist-to-hip ratio; DEXA scan for true body composition; or a BIA smart scale (Renpho, Withings) for trend tracking, accepting that the absolute number drifts.
What the result actually means
The BMI number tells you where your weight-to-height ratio sits in a population distribution. It does not tell you how much of that weight is muscle, how much is fat, or where the fat is stored (visceral abdominal fat carries the metabolic risk; subcutaneous fat largely does not). If your BMI is 27 and you carry visible muscle, your real risk profile is closer to a BMI 23 sedentary peer than to a BMI 27 sedentary peer.
For South Asian, East Asian, and Southeast Asian adults, the WHO Expert Consultation in Lancet 2004 recommended lower action points (overweight at BMI 23, high risk at 27.5) because Asian populations carry more visceral fat at lower BMI. If your background falls in this group, mentally shift the gauge: a BMI of 24 is closer to overweight territory than to normal territory in terms of cardiometabolic risk.
Pharmacist take
BMI cannot account for the body composition shifts caused by common medications. Corticosteroids (prednisone), antipsychotics (olanzapine, quetiapine), and insulin all drive weight gain that BMI registers without distinguishing fat from fluid. SSRIs and mirtazapine often add 3 to 5 kg over the first 6 months on therapy. If you are on any of these and your BMI moved into a new category, the cause is likely the drug, not your habits, and your prescriber needs to see the trajectory.
Halal, Canadian, and dietary considerations
The Canadian multicultural health context matters here. Statistics Canada data shows roughly 1 in 4 Canadians are visible minorities, and South Asian Canadians are the largest visible minority group. If you fall in this demographic, the standard Canadian primary-care BMI chart will systematically understate your cardiometabolic risk. Ask your GP for waist circumference and an HbA1c instead of treating BMI as the screening endpoint.
Methodology and sources
The categories shown match NHLBI's adult BMI classification, which mirrors the WHO 1995 cutoffs. The Asian-specific thresholds discussed are from the WHO Expert Consultation, Lancet 2004. The waist circumference cutoffs reference Health Canada body weight classification guidance.
Understanding Your BMI Result
Body Mass Index (BMI) is the quickest way to check whether your weight is in the healthy range for your height. Developed by Belgian statistician Adolphe Quetelet in the 1830s and adopted as a public health screening tool by the WHO in 1985, BMI remains the most widely-used weight classification method worldwide — though it's not without limitations.
BMI is calculated as weight in kilograms divided by height in meters squared (kg/m²). The WHO classifies a BMI below 18.5 as underweight, 18.5–24.9 as normal, 25–29.9 as overweight, and 30 or higher as obese. These categories correlate with statistical risk for cardiovascular disease, type 2 diabetes, and certain cancers — but correlation isn't destiny, and individual health varies widely.
The biggest limitation of BMI is that it treats all body mass the same. A bodybuilder with 8% body fat and a sedentary office worker with 30% body fat can have identical BMIs because BMI can't distinguish muscle from fat. This is why athletes frequently register as 'overweight' or 'obese' despite being extremely lean. BMI also doesn't account for bone density, fluid retention, or fat distribution — abdominal fat (visceral) carries more health risk than fat stored in hips or thighs.
For most adults aged 20-65 with average activity levels, BMI provides a reasonable first screen. If you're athletic, pregnant, postpartum, elderly, of Asian descent (where health risks start at BMI 23 rather than 25), or recovering from illness, pair BMI with other metrics: waist-to-hip ratio, body fat percentage, or a DEXA scan. A qualified healthcare provider can interpret your BMI in the context of your full health picture.
Keep learning
- →BMI Explained: What Your Number Really MeansDeep-dive into BMI interpretation, limitations, and alternatives.
- →How to Lose Belly Fat (Science-Based)Visceral fat is what BMI misses. Here's how to target it.
- →How Much Protein Do You Need?Preserve muscle while losing weight — the protein math.
- →Maintenance Calorie CalculatorOnce you know your BMI, calculate the calories to reach goal weight.
BMI Calculator FAQ
BMI (Body Mass Index) is a simple screening metric calculated by dividing your weight in kilograms by your height in meters squared (kg/m²). It provides a rough estimate of body fatness based on height and weight alone.
BMI does not distinguish between muscle and fat mass. Athletes, bodybuilders, and people with above-average muscle mass often show an 'overweight' BMI despite being healthy and lean. In these cases, body fat percentage or waist circumference are better indicators.
The WHO classifies a BMI between 18.5 and 24.9 as 'normal weight.' Below 18.5 is considered underweight, 25-29.9 is overweight, and 30+ is classified as obese. However, these ranges are population-level guidelines — individual health depends on many factors beyond BMI.
For general health monitoring, checking BMI once a month is sufficient. If you are actively losing or gaining weight, weekly checks can help track trends. Remember that daily fluctuations in water weight are normal and do not reflect real changes in body composition.
The standard BMI formula does not adjust for age or gender, though body composition changes with both. Older adults naturally lose muscle mass, meaning the same BMI may represent more body fat. Some health organizations use adjusted thresholds for elderly populations.