Calculate your Body Mass Index, resting calorie burn, and daily energy needs in seconds.
Your Body Mass Index (BMI) is one of the most widely used screening tools in medicine, giving a quick snapshot of body weight relative to height. While it has limitations, it remains a useful starting point for understanding health risk. This calculator also estimates your Basal Metabolic Rate (BMR) — the calories your body burns at rest — and your Total Daily Energy Expenditure (TDEE), which accounts for physical activity.
BMR uses the Mifflin-St Jeor equation. TDEE adjusts for activity level. Calorie targets are for information only — consult a registered dietitian or physician before making significant dietary changes.
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Increased risk of malnutrition, osteoporosis, anemia |
| 18.5 – 24.9 | Normal Weight | Lowest overall health risk |
| 25.0 – 29.9 | Overweight | Elevated risk of heart disease, type 2 diabetes |
| 30.0 – 34.9 | Obese (Class I) | High risk of chronic conditions |
| 35.0 – 39.9 | Obese (Class II) | Very high risk |
| 40.0 and above | Obese (Class III) | Extremely high risk, surgical intervention may be considered |
Your Basal Metabolic Rate (BMR) is the number of calories your body requires to perform basic life-sustaining functions while at complete rest — breathing, circulation, cell production, and temperature regulation. Think of it as your body's "idle speed."
We calculate BMR using the Mifflin-St Jeor equation, which is widely considered the most accurate formula for most adults:
BMR is useful because it tells you the absolute minimum calories needed to sustain life. Even if you stayed in bed all day, you'd still burn this many calories.
Your Total Daily Energy Expenditure (TDEE) multiplies your BMR by an activity factor that accounts for how much you move throughout the day. It's the total number of calories you burn in a typical 24-hour period.
TDEE is sometimes called your "maintenance calories" — eat at this level and your weight stays stable. Eat below it (a caloric deficit) to lose weight; eat above it (a caloric surplus) to gain weight or muscle mass.
A 500-calorie daily deficit creates roughly 1 lb of fat loss per week, since one pound of fat contains approximately 3,500 calories. However, very large deficits can lead to muscle loss, fatigue, and nutrient deficiencies, so most health professionals recommend gradual, sustainable deficits of 300–600 calories per day.
⚠️ Important: BMI and calorie calculators provide estimates. They don't account for muscle mass, bone density, age-related changes, or medical conditions. Always consult a healthcare professional before starting a diet or exercise program.
BMI is a useful screening tool, but it has well-documented limitations:
For a more complete picture, many clinicians look at BMI alongside waist circumference, body fat percentage, blood tests, and blood pressure.