Use this weight calculator to estimate your BMI and find your ideal weight based on height, age, and sex. Enter your details in the form above and get results in seconds.
This tool combines a BMI calculator with an ideal weight calculator. It gives you a quick snapshot of where you stand relative to standard healthy weight ranges. Results are estimates, not a diagnosis. They work best as a starting point for conversations with a health care provider.
How the Weight Calculator Uses Your Height and Weight
The calculator asks for your height and weight, along with your age and sex. It uses these inputs to run two calculations at once.
First, it computes your body mass index. BMI divides your weight in kilograms by the square of your height in meters. You can enter your height in feet and inches or centimeters. The tool handles the conversion.
Second, it estimates your ideal body weight using established formulas. These formulas are based on height and adjusted for sex. The result is a suggested ideal weight range, not a single number.
Both outputs appear together so you can compare your current weight to a healthy weight range. If you are tracking weight management over time, bookmark this page and check back as your numbers change.
Calculate Your BMI With the BMI Calculator
To calculate your BMI, enter your height and weight into the form. The BMI calculator returns a number, usually between about 15 and 40 for most adults.
That number falls into a category: underweight, healthy weight, overweight, or obese. The calculator labels the category for you automatically.
You do not need to do any math yourself. Just enter your height in feet and inches (or centimeters) and your weight in pounds (or kilograms), then press calculate.
What Is Body Mass Index (BMI)?
Body mass index is a screening tool that estimates body size in relation to height. It was developed in the 1800s as a population-level statistic and is still widely used by doctors, the CDC, and other health organizations.
BMI does not directly measure body fat. It is a ratio of weight to height. A higher BMI generally suggests more excess body fat, but the number alone cannot tell you how much of your weight is fat versus muscle.
How is BMI calculated? The formula is:
BMI = weight (kg) ÷ height (m)²
If you work in pounds and inches, the formula becomes:
BMI = (weight in lbs × 703) ÷ (height in inches)²
The calculator above handles this automatically, so you only need to enter your numbers.
BMI Categories: Underweight, Healthy Weight, and Overweight
Standard BMI categories for adults (18 years of age and older) are:
- Underweight: below 18.5
- Healthy weight: 18.5 to 24.9
- Overweight: 25.0 to 29.9
- Obese: 30.0 and above
These ranges come from the Centers for Disease Control and Prevention and the Department of Health and Human Services. They apply to males and females of all adult ages using the same thresholds.
A BMI that is considered overweight or obese does not automatically mean poor health. It flags potential health risks worth discussing with a healthcare provider.
Why BMI Falls Between 18.5 and 24.9 for a Healthy Weight Range
The 18.5 to 24.9 range comes from large population studies. Researchers found that adults within this band had the lowest statistical risk for conditions like cardiovascular disease, type 2 diabetes, and certain types of cancer.
Below 18.5, health risks from being underweight (nutrient deficiency, weakened immunity, bone loss) start to rise. Above 24.9, risks linked to excess body fat increase progressively.
These thresholds are a general guideline. Individual factors like age, sex, ethnicity, and body composition can shift where your personal healthy BMI sits. The range is a useful starting point, not a hard rule.
Ideal Weight Calculator: Find Your Ideal Weight
The ideal weight calculator estimates a target weight based on your height and sex. It gives you an ideal weight range rather than a single magic number.
Many factors affect what a healthy weight looks like for you specifically. Frame size, muscle mass, age, and activity levels all play a role. The calculator provides a reference point grounded in clinical formulas.
How the Ideal Weight Calculator Estimates IBW
The calculator uses several well-known formulas to estimate ideal body weight (IBW):
- Devine formula: Originally developed for drug dosing, widely adopted for general ideal weight estimation.
- Robinson formula: A revision of the Devine formula with slightly different coefficients for males and females.
- Miller formula: Tends to produce a somewhat lower ideal weight estimate.
- Hamwi formula: One of the earliest clinical ideal weight formulas, still commonly referenced.
Each formula starts with a base weight for the first 5 feet of height, then adds a set amount per additional inch. The calculator shows results from multiple formulas so you can see an ideal weight range rather than relying on one number.
No single formula is perfect. These are estimates based on height alone. They do not account for body composition, bone density, or current health status.
BMI, Body Fat, and Muscle Mass
BMI is useful, but it has blind spots. The biggest one: it cannot tell the difference between fat and muscle. Two people with the same BMI can have very different body compositions.
Why Body Fat Percentage and Body Composition Matter
Body fat percentage tells you how much of your total body weight is fat. This matters because excess body fat, especially around the organs, drives most weight-related health risks.
Body composition refers to the ratio of fat, muscle, bone, and water in your body. Someone with a healthy body composition may carry more weight on the scale yet face fewer potential health risks than a lighter person with a high body fat percentage.
Methods that measure body fat more directly include DXA scans, skinfold calipers, bioelectrical impedance, and hydrostatic weighing. None are as quick as BMI, but they give a clearer picture when accuracy matters.
How Muscle Mass and Bone Density Affect Your BMI
Muscle is denser than fat. Athletes and people who do regular strength training often have a high BMI despite low body fat. Their weight comes from muscle mass and greater bone density, not excess weight from fat.
On the other end, older adults may lose muscle and bone density over time. Their BMI could appear healthy while their body fat percentage is actually elevated. This is sometimes called "normal weight obesity."
BMI works best as a quick screening tool for the general population. If you have above-average muscle mass, or if age-related changes affect your body size, consider using body fat measurements alongside BMI.
Health Risks of Obesity and Underweight
Both ends of the weight spectrum carry health risks. Maintaining a healthy weight helps reduce your risk for developing several chronic conditions.
Obesity, Cardiovascular Disease, and Diabetes
A BMI of 30 or above is classified as obese. Obesity is linked to:
- Cardiovascular disease (heart disease and stroke)
- Type 2 diabetes
- High blood pressure and cholesterol
- Certain types of cancer
- Sleep apnea
- Joint problems
Fat distribution matters too. Excess weight carried around the waist ("visceral fat") is especially associated with metabolic problems. Waist circumference can be a useful companion measurement to BMI.
Being overweight (BMI 25 to 29.9) also raises risk, though to a lesser degree. Even modest weight loss of 5% to 10% of body weight can improve your health markers significantly.
Weight Loss and Well-being
Reaching and maintaining a healthy weight is about more than a number. Benefits include improved energy, better sleep, easier physical activity, and reduced strain on joints.
Sustainable weight management combines balanced nutrition with regular physical activity. Crash diets rarely work long-term. Small, consistent changes tend to produce better results.
If you are considering weight loss, a health professional can help you set realistic goals based on your current health status, age and sex, activity levels, and many factors specific to you.
BMI Calculator for Children and Adolescence
BMI works differently for children and teens. For anyone under 18 years of age, BMI is calculated the same way but interpreted using age-and-sex-specific growth charts.
A child's weight status is expressed as a percentile rather than a fixed category. For example, a child at the 85th percentile weighs more than 85% of children of the same age and sex. Standard cutoffs used by the CDC are:
- Underweight: below the 5th percentile
- Healthy weight: 5th to 84th percentile
- Overweight: 85th to 94th percentile
- Obese: 95th percentile and above
Children's bodies change rapidly. Growth spurts, puberty, and varying activity levels all affect the numbers. A pediatrician is the best person to interpret a child's BMI percentile and recommend next steps.
This calculator is designed for adults. For children and adolescents, consult your child's health care provider or use a dedicated pediatric BMI tool, such as the one on the CDC gov website.
Limitations of BMI as a Measurement
BMI is a quick, free, and widely available screening tool. It is not a diagnostic tool. Here are its main limitations:
- Does not measure body fat directly. It cannot distinguish between muscle mass, bone density, and fat.
- Same formula for everyone. It does not adjust for age, race, or sex in adults. Studies show that factors can affect how BMI correlates with body fat across different populations.
- Misclassifies muscular individuals. People with high muscle mass may be labeled overweight despite low body fat.
- Misses "normal weight obesity." Some people fall in the healthy BMI range but carry high body fat, especially as they age.
- Does not account for fat distribution. Where fat sits on the body (waist vs. hips) changes health risk, and BMI ignores this.
For a fuller picture of overall health, consider BMI alongside waist circumference, body fat percentage, blood work, blood pressure, and physical activity habits. BMI is one piece of the puzzle, not the whole picture.
When to Talk to a Health Care Provider
Use this calculator as a starting point. Talk to your doctor or healthcare provider if:
- Your BMI is outside the healthy weight range and you are unsure what to do next
- You have existing health conditions like diabetes, high cholesterol, or high blood pressure
- You want a more accurate assessment of body composition
- You are planning significant weight loss or gain
- You are concerned about a child's weight status
A health professional can review your current health status, family history, and lifestyle to give personalized guidance. This weight calculator offers estimates. It does not replace medical advice.
Frequently Asked Questions
Is BMI the Same as Body Fat?
No. BMI is a ratio of weight to height. It does not directly measure body fat. Two people with the same BMI can have very different body fat percentages. BMI is a screening tool that flags when further evaluation may be helpful. To actually measure body fat, you would need methods like DXA, skinfold calipers, or bioelectrical impedance.
What Is a Healthy Weight for My Height and Weight?
A healthy weight generally corresponds to a BMI between 18.5 and 24.9 for adults. Enter your height and weight into the calculator above to see where you fall. Keep in mind that a healthy weight depends on many factors, including body composition, age, and activity levels. The number on the scale is only one indicator.
How much should a 5 ft 4 woman weigh? Using common ideal weight formulas, a woman at 5 feet 4 inches has an estimated ideal weight range of roughly 108 to 145 pounds, depending on the formula. Frame size, muscle mass, and overall health all shift that number. Use the ideal weight calculator above for a personalized estimate.
How Do I Calculate My Ideal Weight as I Age?
The standard ideal weight formulas do not change with age. However, your body composition does. Muscle mass tends to decrease and body fat tends to increase as you get older, even if your weight stays the same.
For adults over 65, some research suggests a slightly higher BMI (around 25 to 27) may be associated with lower mortality risk. This is still debated among researchers. The best approach is to combine weight tracking with regular check-ups, physical activity, and attention to how you feel day to day.
Does This Weight Calculator Replace Medical Advice?
No. This calculator provides estimates based on standard formulas. It is a general guideline, not a diagnosis or treatment plan. For personalized recommendations, especially if you have existing health conditions, consult a qualified health care provider. They can factor in your complete medical history, body composition, and lifestyle in ways a calculator cannot.