BMI Calculator - body mass index in one tap
Calculate your BMI in metric or imperial units. Live result, full WHO categories, healthy weight range and target weight. No sign-up, no ads blocking the inputs. Not medical advice.
- Metric and Imperial
- Full WHO categories
- Healthy weight range
- Works offline
Your BMI
—
Calculated on your device. Nothing is uploaded or saved. How we keep it private
- 100% Secure
- Live Result
- Metric + Imperial
- No Sign-up
- Healthy Range
- WHO Categories
WHO BMI categories
The World Health Organization defines these BMI ranges for adults. The tool tells you which one you fall into.
| Category | BMI range |
|---|---|
| Severe thinness | < 16.0 |
| Moderate thinness | 16.0 - 16.9 |
| Mild thinness | 17.0 - 18.4 |
| Normal weight | 18.5 - 24.9 |
| Overweight (pre-obese) | 25.0 - 29.9 |
| Obese class I | 30.0 - 34.9 |
| Obese class II | 35.0 - 39.9 |
| Obese class III | ≥ 40.0 |
BMI formulas at a glance
The tool computes these for you, but here they are for reference.
| Question | Formula | Example |
|---|---|---|
| BMI formula (metric) | weight (kg) ÷ height (m)² | 70 kg ÷ 1.75² = 22.9 |
| BMI formula (imperial) | 703 × weight (lb) ÷ height (in)² | 154 lb → 703 × 154 ÷ 69² = 22.7 |
| Healthy weight range (metric) | 18.5 - 24.9 × height (m)² | For 1.75 m: 56.7 - 76.3 kg |
| Healthy weight range (imperial) | 18.5 - 24.9 × height (in)² ÷ 703 | For 69 in: 125.2 - 168.5 lb |
Why this is the best BMI calculator
Live result, no ads blocking inputs, honest medical disclaimer.
| Feature | TToolDeck | CDC / NHS | Generic web calculators |
|---|---|---|---|
| No sign-up or email | Yes | Partial | No |
| No ads blocking the inputs | Yes | No | No |
| Live result as you type | Yes | Yes | Yes |
| Metric AND Imperial in one tool | Yes | Partial | Yes |
| Healthy weight range calculated | Yes | Yes | Partial |
| Target weight to reach healthy BMI | Yes | No | No |
| Full WHO sub-categories (16.0-40+) | Yes | Partial | Partial |
| Visual BMI gauge | Yes | Partial | Yes |
| Recent history of calculations | Yes | No | No |
| Works offline after first load | Yes | No | No |
Comparison reflects publicly available information at the time of writing. Features may change. Representative examples of common patterns.
More free calculators
Free browser-based calculators. Nothing uploaded, ever.
BMI Calculator
You are hereBody mass index + healthy range
Percentage Calculator
Five modes with step-by-step breakdown
Unit Converter
11 categories, converts to every unit at once
Age & Date Calculator
Find exact age or days between dates
Loan EMI Calculator
Monthly payment and total interest
Currency Converter
Convert between world currencies
How it works
- 1
Pick units and enter values
Choose Metric (kg, cm) or Imperial (lb, ft/in). Type your weight and height - the result updates as you type.
- 2
See your BMI and category
Your BMI appears with its full WHO category, a visual gauge, and a plain-language explanation of what it means.
- 3
Get your healthy weight range
See the weight range that would put you in the healthy zone for your height - and how much to lose or gain if you are outside it.
Everything you get for free
Metric and Imperial in one tool
Switch between kg/cm and lb/ft+in with a single tap. The result updates instantly - no need to convert your height or weight first.
Full WHO categories
Not just underweight / normal / overweight - the tool uses the full WHO classification: severe, moderate and mild thinness, normal, overweight, and obesity classes I, II and III.
Healthy weight range for your height
See exactly what weight range would put you in the WHO healthy zone for your specific height. Uses 18.5-24.9 BMI as the standard healthy range.
Target weight to reach healthy BMI
If you are outside the healthy range, the tool shows exactly how much weight to lose or gain to reach it. Realistic and actionable - no vague advice.
Visual BMI gauge
A coloured bar shows where your BMI falls on the 10-40 scale. Green for healthy, amber for thin or overweight, red for higher obesity classes.
Copy and share results
One tap to copy your BMI and healthy range, or use your phone's share sheet to send it to yourself or a doctor. Useful for medical follow-ups.
Recent history
The last six calculations are kept (in your browser only) so you can glance back at how your BMI has changed. No account, no cloud, no log.
Clear medical disclaimer
BMI is a screening tool, not a diagnosis. The tool states this and lists the cases where BMI is inaccurate - athletes, pregnant women, children and the elderly.
What people use it for
Check your own BMI
Enter your current weight and height to see your BMI, category and healthy weight range. The starting point for any weight-management plan.
Understand a doctor's feedback
Your doctor mentioned a BMI number - see what it means and where it sits on the WHO scale. Understanding context makes the next appointment more useful.
Track weight goals
See how much you need to lose or gain to reach the healthy range, and use the recent history to track progress over weeks.
Fitness and sports context
If you are into strength training, BMI will run high from muscle. The tool explains this - BMI is a population measure, not a personal verdict.
School and academic work
Students researching public health, nutrition or epidemiology can use the calculator for quick data points and to check WHO category boundaries.
Family health tracking
Parents tracking their adult family members' weight trends can note readings over time. (BMI for children is calculated differently - see a pediatrician.)
Questions people ask
What is BMI?
Body Mass Index (BMI) is a simple number calculated from your weight and height. It was created by the Belgian statistician Adolphe Quetelet in the 1830s as a population-level screening tool. Doctors use it as one quick indicator among many to flag whether a person might benefit from further assessment. It is not a diagnosis, and it is not a measure of body fat.
What is the formula for BMI?
Metric: BMI = weight in kg ÷ (height in meters)². Imperial: BMI = 703 × weight in pounds ÷ (height in inches)². Example: someone who weighs 70 kg and is 1.75 m tall has a BMI of 70 ÷ 3.0625 = 22.9. The tool computes this for you automatically.
What is a healthy BMI?
For most adults, the WHO defines a healthy BMI as 18.5 to 24.9. Below 18.5 is considered underweight; 25 to 29.9 is overweight; 30 and above is classified as obese (with three sub-classes at 30, 35 and 40). These thresholds are population averages and may not fit every individual.
Is BMI accurate?
BMI is a useful screening tool but has important limits. It cannot tell the difference between muscle and fat - a muscular athlete can have a BMI of 27 while being very lean. It also does not account for fat distribution (belly fat vs. hip fat), age, sex, ethnicity or pregnancy. It works best as a first-pass indicator for large populations.
Is BMI different for men and women?
The formula is the same, but the interpretation is slightly different. Women naturally carry more body fat than men at the same BMI, and the healthy range is sometimes adjusted. The tool lets you enter sex for a general note, but the WHO cutoffs are technically the same for both.
Does BMI work for children?
No - children and teenagers need a BMI-for-age percentile chart, not the adult BMI categories. The calculation is the same number but the interpretation uses growth curves. Always consult a pediatrician for children and adolescents. This tool is designed for adults only.
Does BMI work for athletes?
BMI can be misleading for athletes and bodybuilders. Muscle is denser than fat, so a muscular person can have a high BMI while having very low body fat. If you train heavily with weights, use body fat percentage or a waist-to-height ratio instead - the tool warns about this.
What if I am pregnant?
BMI is not accurate during pregnancy because it does not account for the weight of the fetus, placenta and amniotic fluid. Use your pre-pregnancy BMI as a reference, and follow the guidance of your healthcare provider.
What is a healthy weight for my height?
The healthy weight range for your height corresponds to BMI values between 18.5 and 24.9. For example, for someone 175 cm (5 ft 9 in) tall, the healthy weight range is roughly 57-76 kg (125-168 lb). The tool calculates this exactly for your own height.
Why is my BMI different from another calculator?
Small differences come from rounding, the exact height/weight you enter, and whether the calculator uses the original formula or the modernized version. The differences are usually tiny (0.1-0.2 BMI points) and do not change the category.
How often should I check my BMI?
Every few months is enough for tracking general trends. Weighing yourself weekly or daily adds noise and can be discouraging. What matters more than any single number is the direction of change over months, plus how you feel and how your clothes fit.
Can this tool replace a doctor?
No. BMI is a screening tool, not a diagnosis. It does not measure body fat, account for muscle, or check blood pressure, blood sugar, cholesterol or any of the other factors that determine health. Use it as one data point, and speak to a healthcare professional for personal medical decisions.
Your data stays on your device
Your weight, height, age and sex never leave your device. The calculation happens entirely in your browser, and the recent history is only kept in your session - gone when you close the tab. No server, no log, no retention. Read how we keep it private.