Estimate BMI, daily calories, macros, and other health metrics. Not medical advice.
Health calculators estimate key metrics like BMI, daily calorie needs, and macronutrient targets using validated scientific formulas. These tools are useful for general health awareness and personal planning — they are not a substitute for medical advice. Individual health is complex and influenced by factors these calculators cannot measure. Always consult a qualified healthcare provider before making significant changes to diet, exercise, or medical treatment.
Calculate your BMI and see your adult weight category.
Open calculator →Find your daily calorie target for maintenance, weight loss, or gain.
Open calculator →Get daily protein, carb, and fat targets from your calorie goal.
Open calculator →Calculate calories burned at rest using BMR formulas.
Open calculator →Find your daily calorie needs based on activity level.
Open calculator →Estimate body fat % with the US Navy method.
Open calculator →Estimate ideal weight using 4 clinical formulas.
Open calculator →Calculate WHtR and assess abdominal fat risk.
Open calculator →Calculate daily protein needs by weight and activity.
Open calculator →To understand your weight category relative to height: BMI Calculator. To estimate body fat percentage using circumference measurements (no calipers needed): Body Fat Calculator (US Navy method). To find healthy weight ranges for your height and frame using four validated formulas: Ideal Weight Calculator. To estimate resting calorie burn: BMR Calculator. To estimate total daily calories including activity: TDEE Calculator or Calorie Calculator. To set daily protein, carbohydrate, and fat targets: Macro Calculator. For medical interpretation of any of these metrics, speak with a doctor or registered dietitian.
Body Mass Index (BMI) is calculated from height and weight. It is a useful population-level screening tool that correlates with health risks at the extremes, but it has well-documented limitations for individuals. BMI cannot distinguish between muscle and fat — a muscular athlete may have the same BMI as a sedentary person with high body fat. It also does not account for fat distribution, bone density, age-related body composition changes, or ethnicity-based differences in risk thresholds. The WHO, CDC, and most medical organizations recommend treating BMI as one data point to discuss with a healthcare provider, not as a standalone health verdict. This calculator uses adult BMI categories (18 and older); children and teens require age- and sex-specific BMI percentile charts.
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain basic functions — breathing, circulation, organ function, and temperature regulation. Total Daily Energy Expenditure (TDEE) multiplies your BMR by an activity factor to estimate how many calories you actually burn in a typical day. This site uses the Mifflin-St Jeor equation, which was validated in a 1990 study and is regarded as the most accurate of the common BMR formulas for general use. The activity multipliers are approximate categories — 'moderately active' for someone who exercises 3 to 5 days per week, for example. These are estimates; individual metabolism varies by genetics, hormonal status, health conditions, and the composition of your diet.
Macronutrients are the three major nutrients that provide calories: protein (4 calories per gram), carbohydrates (4 calories per gram), and fat (9 calories per gram). The Macro Calculator divides a calorie target into gram targets for each macronutrient based on your fitness goal. Higher protein intake is consistently associated with better muscle preservation during calorie restriction, improved satiety, and favorable body composition outcomes. Common splits: a balanced maintenance diet might use 40% carbs, 30% protein, 30% fat; a weight-loss diet may emphasize protein at 40% with reduced carbs; a ketogenic diet uses roughly 70% fat, 25% protein, and 5% carbs. The right split depends on your goals, food preferences, and any medical or dietary restrictions — a registered dietitian can personalize this further.
The Body Fat Calculator uses the US Navy circumference method, which estimates body fat percentage from waist, neck, and (for women) hip measurements — no body fat calipers or DEXA scan required. The formula was developed by the US Navy for field assessment and validated against hydrostatic (underwater) weighing. For men, the formula uses waist and neck circumference; for women, it adds hip circumference to account for typical fat distribution differences. The method has a margin of error of roughly ±3–4 percentage points compared to more precise laboratory methods, and it may be less accurate for athletes or individuals with unusual fat distribution. Healthy body fat ranges: men 8–19%, women 21–33% (American College of Sports Medicine guidelines). These are reference ranges — not medical thresholds. Body fat goals should be discussed with a healthcare provider.
The Ideal Weight Calculator computes healthy weight ranges using four validated formulas: Devine (1974, the clinical standard for medication dosing), Robinson (1983), Miller (1983), and Hamwi (1964, widely used in clinical nutrition). Each formula was derived from different study populations and uses slightly different coefficients, producing a range of values rather than a single number. The average of these four formulas gives a reasonable midpoint estimate. The primary limitation of all ideal weight formulas is that they use only height and sex — not age, muscle mass, bone density, or frame size. A competitive athlete may healthily weigh significantly more than the formula output; an older adult may healthily weigh less. These numbers are reference points for clinical calculations (like medication dosing using adjusted body weight), not personal weight goals. Discuss weight goals with a doctor or registered dietitian.
A sustained calorie deficit of approximately 500 calories per day is associated with about 1 pound of weight loss per week — this rate is generally considered safe and sustainable by major health organizations. Deficits below 1,200 calories per day for women or 1,500 per day for men are associated with nutrient deficiencies, muscle loss, and metabolic adaptation and are not recommended without medical supervision. Conversely, a 500-calorie daily surplus above maintenance is associated with roughly 1 pound of weight gain per week. Individual results vary significantly based on starting weight, activity level, diet composition, and metabolic adaptation. These calculators provide a starting point; adjusting based on real-world results over 2–4 week periods is a more reliable approach than targeting precise numbers.