BMI Calculator – Understand Your Body Mass Index, Ideal Weight, BMR and Daily Calories
This BMI Calculator from MyTimeCalculator is an all-in-one health and weight tool that helps you estimate your Body Mass Index (BMI), understand your weight category, find a healthy weight range, and estimate your daily calorie needs using BMR (Basal Metabolic Rate) and activity level. It supports both metric (kg, cm) and US (lb, ft/in) units and allows you to switch between global WHO BMI categories and Asian BMI cutoffs that are often used for South and East Asian populations.
BMI is a long-standing and widely used screening measure thatates weight to height. While it does not directly measure body fat, it offers a simple, standardized way to classify body weight and evaluate general health risk in adults. Combined with BMR and daily calorie estimates, this calculator gives you a quick yet powerful snapshot of your current weight status and overall energy requirements.
What You Can Do with This BMI Calculator
The tool is divided into three main tabs so you can look at your body measurements from several angles:
- Standard BMI (Adults): Quickly calculate your BMI using WHO categories and see an estimated ideal weight range for your height.
- Region-Based BMI (WHO vs Asian): Compare how your BMI is classified under global WHO cutoffs and Asian BMI ranges, which use lower thresholds for overweight and obesity.
- BMI + BMR & Daily Calories: Combine BMI with BMR and estimated daily calorie needs based on age, sex and activity level for a fuller health and weight overview.
By switching between these tabs, you can see not only where you stand today, but also how changing your weight or activity level might affect your long-term health.
What Is BMI (Body Mass Index)?
Body Mass Index is a simple numerical index that compares your weightative to your height. Instead of looking at weight alone, BMI normalizes your weight for your height so that a taller person and a shorter person with the same BMI are in a similar weight category, even though their absolute weights might differ.
BMI Formula (Metric and US)
In metric units, BMI is calculated as:
In US units (pounds and inches), BMI is calculated as:
The calculator handles the unit conversions for you. When you choose metric, it uses kilograms and centimeters; when you choose US units, it uses pounds and inches and applies the appropriate formula automatically.
Why BMI Is Used
BMI is not a perfect measure, but it is:
- Simple: It only requires height and weight.
- Standardized: The same formula is used globally, so it is easy to compare results.
- Evidence-based: Population studies have linked BMI ranges to the risk of conditions like type 2 diabetes, heart disease and some cancers.
For most adults, BMI is a reasonable starting point to discuss weight and health. However, it should be viewed as a screening tool, not a final diagnosis.
WHO BMI Categories – Global Adult Classification
The World Health Organization (WHO) BMI categories are commonly used for adults worldwide. These ranges are:
- Underweight: BMI < 18.5
- Normal weight: BMI 18.5 – 24.9
- Overweight: BMI 25.0 – 29.9
- Obesity (Class I, II, III): BMI ≥ 30.0
In general, BMI in the “Normal weight” range is associated with the lowest risk of many weight-related health problems. BMI in the “Overweight” or “Obesity” ranges is associated with higher risk, especially when combined with other factors such as age, high blood pressure, high blood sugar, smoking or a family history of disease.
Asian BMI Cutoffs – Why They Are Different
For many South Asian and East Asian populations, health risks like type 2 diabetes and cardiovascular disease can start at lower BMI levels than in Western populations. To reflect this, Asian-specific BMI ranges were proposed using lower thresholds for overweight and obesity.
Commonly used Asian BMI cutoffs are:
- Underweight: BMI < 18.5
- Normal: BMI 18.5 – 22.9
- Overweight: BMI 23.0 – 24.9
- Obese: BMI ≥ 25.0
The Region-Based tab of this BMI Calculator allows you to compare your BMI against both WHO and Asian categories so you can see how your weight is interpreted under each system. This is especially useful if you live in or have a family background from regions where smaller body frames are common and risk begins at lower BMI values.
Ideal Weight Range for Your Height
Many people ask, “What should my ideal weight be?” While there is no single perfect number, BMI-based healthy range gives a practical estimate. Using the WHO “Normal” range of 18.5 to 24.9, the calculatorerses the BMI formula to compute a weight range that would place you within that interval.
For example, if your height is 170 cm (or the equivalent in inches), the calculator calculates the minimum weight for BMI 18.5 and the maximum for BMI 24.9, then shows the resulting range in kilograms or pounds.
This ideal weight range is not a rigid target but a helpful reference window. Where you should aim within that range depends on your body structure, muscle mass, health status and guidance from your doctor or dietitian.
BMR (Basal Metabolic Rate) – Your Resting Energy Needs
BMR is the number of calories your body needs every day just to keep you alive at rest – to maintain breathing, circulation, temperature, basic organ function and other vital processes. It does not include movement, exercise, work or daily activities.
The BMI + BMR tab in this calculator uses the Mifflin–St Jeor equation, which is widely accepted for estimating BMR:
For men:
For women:
After your BMR is estimated, the calculator multiplies it by an activity factor based on your selected activity level to estimate your total daily calorie needs.
Activity Factors Used in This Calculator
- Sedentary (1.2): Little or no exercise, mostly sitting.
- Lightly active (1.375): Light exercise 1–3 days per week.
- Moderately active (1.55): Moderate exercise 3–5 days per week.
- Very active (1.725): Hard exercise 6–7 days per week.
- Super active (1.9): Very hard exercise or physically demanding job.
The result is your estimated daily calorie requirement to maintain your current weight. Eating below that level over time tends to result in weight loss, and eating above it tends to result in weight gain, assuming other factors are stable.
How To Use the BMI Calculator Step-by-Step
1. Standard BMI Tab (Adults)
- Select your unit system: Metric (kg, cm) or US (lb, ft/in).
- Enter your height and weight.
- Click “Calculate BMI”.
The calculator will show:
- Your BMI value
- Your WHO weight category (Underweight, Normal, Overweight, Obesity)
- An estimated ideal weight range for your height
- A general note reminding that BMI is a screening tool only
2. Region-Based BMI Tab (WHO vs Asian)
- Choose the region standard: Global / WHO or Asian categories.
- Select your unit system and enter height and weight.
- Click “Calculate Region-Based BMI”.
You will see:
- Your BMI (same numeric value as standard BMI)
- Your category under the selected standard
- A brief explanation of the standard used and why its thresholds differ
You can run the calculation multiple times, switching between WHO and Asian categories to see how your classification changes with each system.
3. BMI + BMR & Daily Calories Tab
- Select your unit system.
- Choose your sex (male or female).
- Enter your age, height and weight.
- Select your activity level from the dropdown.
- Click “Calculate BMI, BMR & Calories”.
The results include:
- Your BMI value and WHO BMI category
- Your estimated BMR (resting calories per day)
- Your estimated daily calorie needs based on activity level
Using BMI, BMR and Calories Together
On their own, each of these indicators tells you something useful. Together, they give a more complete picture:
- BMI shows if your weight is classified as underweight, normal, overweight or obese.
- Ideal weight range shows a target window based on BMI for your height.
- BMR shows how many calories your body uses at rest.
- Daily calories estimate how much energy you need based on your lifestyle.
From there, you can explore weight loss, maintenance or gain strategies. For example, if your daily maintenance calories are estimated at 2,300 kcal and you want to lose weight, you might aim for a moderate deficit (such as 300–500 kcal per day) after consulting a professional.
Limitations of BMI – What It Does Not Show
BMI is useful, but it has important limitations:
- Does not measure body fat directly: A high BMI can be due to muscle, not fat.
- May misclassify athletes: Fit individuals with high muscle mass can be labeled “overweight” or “obese”.
- Does not consider fat distribution: Two people with the same BMI can have very different health risks if one carries more fat around the waist.
- Not designed for children, teens, pregnant or very elderly: Separate growth charts or clinical tools are used for these groups.
Because of these limitations, BMI should be interpreted alongside other factors like waist circumference, body composition, blood pressure, blood sugar, cholesterol and family history.
Other Helpful Health Calculators on MyTimeCalculator
For a broader picture of your health and fitness, you may find the following tools on MyTimeCalculator helpful:
- BMR Calculator – Focus exclusively on resting calorie needs.
- Daily Calorie Calculator – Estimate calories for weight loss, maintenance or gain.
- Ideal Weight Calculator – Explore healthy weight targets using several formulas.
- Body Fat Calculator – Estimate body fat percentage using simple measurements.
- Waist-to-Hip Ratio Calculator – Assess abdominal fat distribution and risk.
- Heart Rate Calculator – Estimate maximum and target heart rate zones for exercise.
Combining BMI with these additional measures can give you a more accurate and personalized understanding of your health than BMI alone.
Practical Tips for Interpreting Your BMI and Calorie Results
- If your BMI is in the “Normal” range: Focus on maintaining your weight with balanced nutrition, regular activity, and sufficient sleep.
- If your BMI is “Underweight”: Discuss with a healthcare provider whether you should gain weight, and explore calorie-dense, nutrient-rich foods.
- If your BMI is “Overweight” or “Obese”: Consider gradually improving your eating patterns, increasing physical activity and working with a professional on a realistic, sustainable plan.
- Use the daily calorie estimate as a guide, not an absolute rule: Real-life energy needs can vary based on genetics, hormones, stress and other factors.
Remember that rapid, extreme dieting or over-exercising can be harmful. Sustainable changes, such as small calorie reductions, more whole foods, regular movement and good sleep, usually work better long term than aggressive short-term fixes.
Medical Disclaimer
This BMI Calculator is for general informational and educational purposes only. It does not provide medical advice, diagnosis or treatment. BMI, BMR and calorie estimates are approximations and may not reflect your exact health status or energy needs. Always consult a qualified healthcare professional before making changes to your diet, exercise routine, medication or lifestyle based on calculator results.
BMI Calculator FAQs
Frequently Asked Questions BMI, Ideal Weight and BMR
Find clear answers to common questions BMI, Asian vs WHO cutoffs, ideal weight ranges, BMR and daily calorie estimates.
BMI is an indirect measure of body fat. It uses height and weight only and does not distinguish between muscle, bone and fat. For most adults, it gives a reasonable estimate of weight-related health risk, but it may misclassify very muscular people or those with unusual body composition. For a more complete picture, combine BMI with other measurements such as waist circumference or a Body Fat Calculator.
Research suggests that many Asian populations have a higher risk of conditions like diabetes and cardiovascular disease at lower BMI values than Western populations. Because of this, Asian BMI categories typically define “overweight” beginning at BMI 23 and “obese” at BMI 25. The Region-Based tab lets you see how your BMI fits into those cutoffs.
BMI may classify muscular individuals as overweight or obese even when their body fat is low. In these cases, BMI is less useful on its own. Athletes often need additional assessments such as body fat percentage, performance metrics and medical screening to evaluate health more accurately.
No. Standard adult BMI cutoffs do not apply to children and teenagers. Pediatric BMI uses age- and sex-specific growth charts. If you are interested in BMI for a child or teenager, consult a pediatrician or a growth chart from a trusted health authority instead of adult BMI ranges.
For most people, checking BMI periodically (for example, every few months) is sufficient. BMI does not usually change significantly from week to week. If you are actively working on weight loss or gain, you may focus more on body weight, body measurements, energy levels and guidance from a professional rather than daily BMI changes.
According to WHO, a healthy BMI range for most adults is between 18.5 and 24.9. However, for Asian populations, some guidelines consider 18.5–22.9 as the preferred range, with increased risk beginning at BMI 23. Always interpret these ranges in context with your personal health history and your doctor’s advice.
Your daily calorie estimate approximates the intake needed to maintain your current weight. To lose weight, many people aim for a moderate calorie deficit (for example, 300–500 kcal below maintenance) through a combination of diet changes and increased activity. To gain weight, some aim for a modest surplus above maintenance. The exact numbers and pace that are safe for you should be confirmed with a healthcare or nutrition professional.
No. BMI is just one part of the picture. Health risk is influenced by many factors, including age, genetics, blood pressure, blood sugar, cholesterol, smoking status, physical activity, diet and how fat is distributed around your body. For example, waist size and waist-to-hip ratio provide additional information on abdominal fat and risk. Use BMI as a starting point, not a final judgment.
No. This calculator is not a substitute for professional medical advice. Never change prescription medications, start extreme diets or make significant lifestyle changes solely on the basis of BMI, BMR or calorie estimates. Always discuss your results and plans with a qualified healthcare provider before acting.