BMI Calculator
Calculate your BMI instantly in metric or US units. See your WHO category, healthy weight range, and goal weight - free and 100% private.
Enter your height and weight to see your BMI.
Features
100% Browser-Based
Your weight and height are never sent anywhere. Every calculation happens locally in your browser.
Free & No Sign Up
No registration, no limits, no hidden fees. Just open and use.
Instant Results
Your BMI updates live as you type - no Calculate button, no waiting.
Metric & US Units
Enter centimeters and kilograms or feet, inches, and pounds. Switching units converts your values automatically.
More Than a Number
See your WHO category on a visual scale, the healthy weight range for your height, and how many kilos or pounds separate you from it.
How to Calculate Your BMI?
- Pick Metric (cm, kg) or US (ft, in, lb) units - your values convert when you switch.
- Enter your height and weight - the BMI updates live as you type.
- Check the visual scale to see which WHO category you fall in.
- Read the healthy weight range for your height and how far you are from it.
Common Use Cases
Health Screening
Get a quick, standardized read on whether your weight is in a healthy range for your height before a checkup.
Weight Goal Planning
Find the healthy weight range for your height and the exact number of kilos or pounds to lose or gain.
Fitness Tracking
Recheck your BMI periodically as you train and diet to see the trend, not just a single snapshot.
Insurance & Forms
Many applications ask for BMI. Compute it privately here without uploading your measurements anywhere.
Tips for Interpreting Your BMI
- ✓ Weigh yourself in the morning, after the bathroom and before eating or drinking, for the most consistent readings.
- ✓ BMI ignores body composition - muscular people often read 'overweight' while carrying little fat.
- ✓ Track the trend, not the snapshot: a BMI moving from 29 to 26 over months says more than any single number.
- ✓ Waist circumference adds context the BMI misses - above 94 cm (37 in) in men or 80 cm (31.5 in) in women raises health risk.
Frequently Asked Questions
Is my weight or height sent to any server?
No. The BMI calculator runs entirely in your browser using client-side JavaScript - your weight, height, and results are never transmitted, stored, or logged anywhere outside your device. This matters because body measurements are sensitive health information that many people prefer to keep private, whether out of medical confidentiality concerns or simple personal comfort. You can verify it yourself: open your browser's DevTools Network tab, enter your values, and watch - zero requests leave your device. Unlike many health websites that log inputs for analytics, ToolsMio has no server-side component involved in the calculation at all.
How is BMI calculated?
BMI equals your weight in kilograms divided by the square of your height in meters (kg/m²). If you use US units, the tool converts pounds and inches to metric first, then applies the same formula - the result is identical. The WHO classifies adults as underweight below 18.5, normal weight from 18.5 to 24.9, overweight from 25 to 29.9, and obese at 30 and above. The scale is the same for men and women, and for all adult ages. The tool also shows the healthy weight range for your height - the weight span that keeps your BMI between 18.5 and 24.9 - which is usually the more actionable number.
Is BMI accurate for everyone?
BMI is a useful population-level screening measure, but it has known limitations for individuals. Because muscle is denser than fat, very muscular people - athletes, bodybuilders, manual laborers - can register as overweight or obese while carrying little fat. Conversely, it can underestimate body fat in older adults or people who have lost muscle. BMI also does not distinguish where fat is stored, and visceral (abdominal) fat carries higher health risks than fat distributed elsewhere. For children and teenagers, adult BMI cutoffs do not apply; age- and sex-specific percentile charts are used instead. Treat your BMI as a starting point for a conversation with a healthcare provider, not a diagnosis.
What BMI should I aim for?
For most adults, the WHO healthy range is a BMI between 18.5 and 24.9. If your BMI falls outside it, the tool shows exactly how much weight separates you from the nearest edge of the range - losing or gaining that amount gradually (0.25-0.5 kg or 0.5-1 lb per week) is the sustainable approach. Keep in mind that risk is a gradient, not a cliff: a BMI of 25.2 is meaningfully different from one of 34. And if you are athletic, older, or pregnant, the standard range may not be the right target for you. Combining this tool with the calorie calculator can help you plan a realistic path to a healthy weight.
Why does the calculator need to know units - can I use pounds and inches?
Yes. The tool has a metric/imperial toggle: metric mode takes height in centimeters and weight in kilograms, while US mode takes height in feet plus inches and weight in pounds. If you switch modes after entering values, your measurements convert automatically so you never retype them. Internally every calculation is done in metric (kg/m²), which is the form the WHO classification is defined in - using US units cannot change your result, only how you enter it.