Body & Weight

BMI Calculator

Calculate your Body Mass Index, BMR, TDEE, healthy weight range, BMI Prime, and Ponderal Index — plus daily calorie goals and macro targets. Ages 2-120.

Step 1 — Enter Your Details
Results update instantly as you type
ages 2–120
Step 2 — Your Results
✓ Live
Body Mass Index
Share
1018.5253050
24.5
BMI
Normal
0.98
BMI Prime
14.0
Ponderal Index
56.7–76.3 kg
Healthy Range
1,709
BMR kcal/day
At complete rest
2,649
TDEE kcal/day
Moderately Active
WHO Classification
Severe Thinness< 16
Moderate Thinness16-17
Mild Thinness17-18.5
Normal18.5-25You
Overweight25-30
Obese Class I30-35
Obese Class II35-40
Obese Class III> 40
Daily Calorie Goals
Weight Loss
Lose 1 lb/week
2,149
kcal/day
Mild Loss
Lose 0.5 lb/week
2,399
kcal/day
Maintain
Current weight
2,649
kcal/day
Mild Gain
Gain 0.5 lb/week
2,899
kcal/day
Weight Gain
Gain 1 lb/week
3,149
kcal/day
🥩 Recommended Macrosat maintenance
199g
Protein
30%
265g
Carbs
40%
88g
Fat
30%
30%
40%
30%

For a goal-specific split, use the Macro Calculator →

⚠️ Risks of Being Overweight
  • High blood pressure and cardiovascular strain
  • Elevated LDL cholesterol and triglycerides
  • Type II diabetes — significantly increased risk
  • Coronary heart disease and stroke
  • Gallbladder disease and osteoarthritis
  • Sleep apnoea and breathing problems
  • Certain cancers (endometrial, breast, colon, kidney)
  • Increased risk of mortality vs healthy BMI range
⚠️ Risks of Being Underweight
  • Malnutrition, vitamin deficiencies, and anaemia
  • Osteoporosis — increased bone fracture risk
  • Decreased immune function and slower recovery
  • Growth and development issues in children and teens
  • Reproductive complications for women (hormonal imbalance)
  • Surgical complication risk
  • Increased risk of mortality vs healthy BMI range
📚 Understanding These Metrics

⚖️ BMI

Calculated as weight ÷ height². Widely used but does not distinguish fat from muscle — athletes may score 'overweight' despite low body fat.

📐 BMI Prime

Your BMI divided by 25. Below 0.74 = underweight; 0.74–1.0 = normal; above 1.0 = overweight; above 1.2 = obese.

📏 Ponderal Index

Cubes height rather than squaring it: weight (kg) ÷ height³ (m). More reliable for very tall or very short individuals. Normal: 11–14 kg/m³.

🔥 BMR

Calories burned at complete rest. Calculated via Mifflin-St Jeor equation. Has ±10% variance.

⚡ TDEE

BMR × activity multiplier. Your maintenance calorie baseline. Eat less to lose, more to gain.

📐 BMI Formula

Metric (SI)
BMI = weight (kg) ÷ height² (m)
Example: 72.57 ÷ 1.778² = 23.0
US Customary
BMI = 703 x weight (lbs) ÷ height² (in)
Example: 703 x 160 ÷ 70² = 23.0

Related Nutrition Calculators

Use these tools alongside your BMI for a complete picture of your health and nutrition.

Calorie Calculator
Daily calorie needs
Open
Macro Calculator
Protein, carbs & fat
Open
TDEE Calculator
Total energy expenditure
Open
Body Fat %
US Navy method
Open
Ideal Weight
Hamwi · Miller · Robinson
Open
Calorie Deficit
Reach your goal weight
Open
Protein Intake
Goal-based targets
Open
Water Intake
35 ml/kg + exercise
Open

What Is BMI and How Is It Used?

BMI (Body Mass Index) is a measurement of a person's leanness or corpulence based on height and weight, intended to quantify tissue mass. It is widely used as a general indicator of whether a person has a healthy body weight for their height.

The value is used by the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) as a population-level screening tool.

BMI for Children and Teens (Ages 2–20)

For children and adolescents, the CDC uses BMI-for-age percentiles: below the 5th percentile is underweight, 5th–85th is healthy weight, 85th–95th is at risk of overweight, and above the 95th percentile is overweight.

Limitations of BMI

Athletes & bodybuilders

Muscle is denser than fat. A bodybuilder may register as "overweight" despite very low body fat.

Older adults

Older adults have more body fat relative to their BMI. A healthy BMI in an inactive older adult may still carry risks.

Ethnic variation

Several Asian countries use BMI 23 for "overweight" (vs 25) due to increased health risks at lower BMI values.

Children & adolescents

Fixed adult thresholds should never be applied to under-18s — always use age-specific percentile charts.

Frequently Asked Questions

What is a healthy BMI for adults?

According to the WHO, a healthy BMI for adults is between 18.5 and 24.9 kg/m². Below 18.5 is underweight; 25–29.9 is overweight; 30 and above is obese.

Is BMI accurate for women vs men?

BMI uses the same thresholds for both sexes, but women naturally carry more body fat than men at the same BMI value. For a more sex-specific measure, use the body fat percentage calculator.

Can I have a normal BMI but still be unhealthy?

Yes. A sedentary person with very little muscle mass can have a normal BMI with high body fat percentage and still face metabolic health risks. Waist circumference and activity levels also matter.

What is BMI Prime and why does it matter?

BMI Prime is your BMI divided by 25. It tells you how far from the upper normal limit you are: 1.0 = exactly at the boundary; below 0.74 = underweight; above 1.2 = obese.

How is the Ponderal Index different from BMI?

The Ponderal Index cubes height rather than squaring it: PI = weight (kg) ÷ height³ (m). This makes it more reliable for very tall or very short individuals. Normal PI: 11–14 kg/m³.

How much weight do I need to lose to reach a healthy BMI?

Your healthy weight range is shown in the results above (BMI 18.5–24.9 for your height). Aim for a 500 kcal/day deficit for ~0.5 kg loss per week.

Go beyond BMI

BMI is a starting point. Get a fuller picture with body fat percentage, waist metrics, and personalised calorie targets.

📏 Body Fat Calculator 📐 Advanced Body Metrics

This tool provides general wellness information and is not medical advice. Consult a healthcare professional before making significant dietary or lifestyle changes.