How to Calculate BMI in kg and feet
Enter your weight in kilograms and your height in feet plus inches to calculate Body Mass Index instantly. This calculator also shows your category, healthy weight range for your height, and a comparison chart.
Formula used: BMI = weight in kg / height in meters squared.
Your BMI Results
Click calculate to see your BMI, category, healthy weight range, and a quick interpretation of the number.
- Enter weight in kilograms.
- Enter height in feet and inches.
- Choose a BMI standard if needed.
Expert Guide: How to Calculate BMI in kg and feet
Body Mass Index, usually called BMI, is one of the simplest screening tools used to estimate whether your weight is low, healthy, high, or in an obesity range relative to your height. If your weight is measured in kilograms and your height is known in feet and inches, you can still calculate BMI very accurately. The only extra step is converting height into meters before applying the formula.
People often search for how to calculate BMI in kg and feet because many countries use a mix of measurement systems. Weight may be taken in kilograms at a clinic or gym, while height is remembered as 5 feet 6 inches, 5 feet 10 inches, or something similar. That mix is very common, and fortunately the math is straightforward once you know the correct process.
What BMI means
BMI is calculated by dividing weight in kilograms by height in meters squared. The result gives a number that falls into recognized ranges used by public health organizations. BMI does not directly measure body fat, but it is widely used because it is inexpensive, quick, and useful for large scale screening. Doctors, public health agencies, researchers, and fitness professionals often use it as a starting point for discussion.
For most adults, BMI can help identify whether further assessment is appropriate. However, it is best understood as a screening number, not a full diagnosis. A muscular athlete may have a high BMI but low body fat. An older adult with low muscle mass could have a normal BMI while still carrying excess body fat. Even so, BMI remains useful because it correlates with health risk at the population level.
The exact BMI formula when weight is in kg and height is in feet
The standard metric formula is:
BMI = weight in kilograms / (height in meters × height in meters)
If your height is given in feet and inches, use this sequence:
- Add total inches. Multiply feet by 12, then add the extra inches.
- Convert inches to meters. Multiply total inches by 0.0254.
- Square the height in meters.
- Divide weight in kilograms by the squared height.
Example: If someone weighs 70 kg and is 5 feet 8 inches tall, the height is 68 total inches. Multiply 68 by 0.0254 to get 1.7272 meters. Next square that height: 1.7272 × 1.7272 = about 2.9832. Finally, divide 70 by 2.9832. The BMI is about 23.5.
Quick shortcut formula using inches directly
If you want a shortcut, you can convert feet and inches into total inches first and then convert to meters as part of one workflow. For example:
- 5 feet 0 inches = 60 inches
- 5 feet 5 inches = 65 inches
- 5 feet 10 inches = 70 inches
- 6 feet 0 inches = 72 inches
Once you know total inches, multiply by 0.0254 to get meters. This is the most reliable way to calculate BMI correctly when your height is remembered in feet.
BMI categories for adults
The table below shows the common adult BMI categories used by major health organizations for general screening. These are the ranges most people refer to when discussing whether BMI is underweight, healthy, overweight, or within obesity classes.
| Adult BMI range | Category | Typical interpretation |
|---|---|---|
| Below 18.5 | Underweight | May indicate inadequate nutrition, illness, or naturally low body mass. Clinical context matters. |
| 18.5 to 24.9 | Healthy weight | Associated with lower average risk for many weight related conditions at the population level. |
| 25.0 to 29.9 | Overweight | Higher average risk for cardiometabolic disease compared with the healthy range. |
| 30.0 and above | Obesity | Associated with significantly higher average risk for hypertension, type 2 diabetes, sleep apnea, and more. |
Some clinical settings also break obesity into Class 1, Class 2, and Class 3. These more detailed cutoffs are useful for risk assessment and treatment planning. For some Asian populations, risk may rise at lower BMI values, so adjusted risk categories are often used.
Worked examples of BMI in kg and feet
Let us go through three practical examples so you can see the process clearly.
- Example 1: 55 kg, 5 feet 2 inches. Height = 62 inches. Height in meters = 62 × 0.0254 = 1.5748. BMI = 55 / (1.5748 × 1.5748) = about 22.2.
- Example 2: 82 kg, 5 feet 9 inches. Height = 69 inches. Height in meters = 1.7526. BMI = 82 / 3.0716 = about 26.7.
- Example 3: 96 kg, 6 feet 0 inches. Height = 72 inches. Height in meters = 1.8288. BMI = 96 / 3.3445 = about 28.7.
These examples show that a relatively small change in height can noticeably affect BMI because height is squared in the formula.
Why height conversion matters
The biggest mistake people make when calculating BMI in kg and feet is using feet as though it were already a metric unit. It is not enough to divide kilograms by feet squared. The height must first be converted properly to meters, or the answer will be wrong. Another common error is forgetting to include the extra inches. For example, 5 feet 10 inches is not the same as 5.10 feet in the BMI formula. The correct path is to convert the full height to inches first, then to meters.
Precision matters because category thresholds such as 24.9 or 25.0 are close together. A small conversion mistake can move someone into the wrong category, especially near cutoffs.
Real public health statistics that explain why BMI is widely used
BMI is popular not because it is perfect, but because it helps public health researchers estimate patterns of weight related risk across large populations. The data below show why BMI remains an important screening tool.
| Population statistic | Figure | Source context |
|---|---|---|
| Adult obesity prevalence in the United States | 41.9% | CDC estimate for 2017 through March 2020 |
| Adult severe obesity prevalence in the United States | 9.2% | CDC estimate for 2017 through March 2020 |
| Childhood obesity prevalence in the United States | 19.7% | CDC estimate covering about 14.7 million children and adolescents |
These figures underscore why simple tools such as BMI calculators are used so often in preventive care and health education. When a screening number suggests increased risk, healthcare professionals may follow up with waist circumference, metabolic markers, blood pressure, diet review, physical activity assessment, and body composition analysis.
How to interpret your BMI result correctly
Once you calculate BMI, the next step is interpretation. If your BMI is below 18.5, the focus may be on nutrition, illness screening, or gaining lean mass where appropriate. If it falls between 18.5 and 24.9, that usually aligns with the standard healthy range for adults. If it is between 25.0 and 29.9, that is considered overweight. If it is 30 or higher, it is classified as obesity.
That said, interpretation should include context:
- Age: Older adults may have different body composition even at the same BMI.
- Sex: Average body fat distribution differs by sex.
- Ethnicity: Health risk can increase at different BMI levels in different populations.
- Muscle mass: Strength athletes may have elevated BMI without excess body fat.
- Waist size: Central fat distribution can add risk independent of BMI.
In other words, BMI is a useful signal, but not the whole picture.
Healthy weight range for your height
One practical use of BMI is estimating a healthy weight range based on the standard 18.5 to 24.9 range for adults. Once height in meters squared is known, you can calculate the lower and upper healthy weights by multiplying height squared by 18.5 and 24.9. This calculator does that automatically.
For example, if your height is 1.70 meters, height squared is 2.89. Multiply 2.89 by 18.5 to get about 53.5 kg. Multiply 2.89 by 24.9 to get about 72.0 kg. That means the standard healthy BMI weight range for 1.70 meters is approximately 53.5 kg to 72.0 kg.
Special cases where BMI has limitations
BMI is not equally accurate for everyone. It should be used carefully in these situations:
- Pregnancy
- Children and teenagers, who use age and sex specific growth charts
- Highly muscular individuals
- Older adults with low muscle mass
- People with edema or conditions affecting fluid balance
For children and adolescents, BMI interpretation is based on percentile charts rather than adult cutoff numbers. That is why a standard adult calculator is not enough for pediatric assessment.
Authoritative resources for BMI guidance
If you want to verify categories and read deeper clinical guidance, use trusted public sources. Good starting points include the Centers for Disease Control and Prevention BMI guidance, the National Heart, Lung, and Blood Institute BMI resources, and the Harvard T.H. Chan School of Public Health explanation of BMI. These sources explain both the strengths and the limitations of BMI.
Step by step summary you can remember
- Write down your weight in kilograms.
- Convert height in feet and inches into total inches.
- Multiply total inches by 0.0254 to convert height to meters.
- Square the height in meters.
- Divide weight in kilograms by height in meters squared.
- Compare the result with adult BMI categories.
If you do this carefully, your result will match standard BMI tools. Online calculators simply automate these exact steps and reduce conversion errors.
Final thoughts
Knowing how to calculate BMI in kg and feet is useful because it lets you interpret health information without needing all measurements in the same system. Whether you are checking your own status, helping a client, or reviewing a clinic report, the process is simple: convert height to meters, square it, and divide your weight in kilograms by that value.
The most important thing is to use BMI wisely. Treat it as a screening tool, not a diagnosis. If your result is outside the healthy range, or if you have health concerns despite a normal BMI, speak with a qualified healthcare professional who can assess body composition, waist size, blood pressure, lab values, and lifestyle habits together.