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Health calculators

Health calculators help you estimate BMI, understand the difference between BMR and TDEE, and work out daily calorie and macro targets. You can also calculate your hydration needs and estimate body fat percentage. Results are indicative only and are not a substitute for professional medical advice — treat them as useful information, not a diagnosis. Pick a calculator below.

Health and physical condition

BMI (Body Mass Index) is calculated by dividing weight in kilograms by the square of height in metres. The WHO classification defines underweight as below 18.5, normal weight as 18.5–24.9, overweight as 25–29.9, and obesity at 30 or above. BMI is a practical screening tool, but it does not account for body composition — athletes with high muscle mass may score in the overweight range despite low body fat. BMR (Basal Metabolic Rate) is the number of calories the body burns at complete rest to sustain vital functions such as breathing and circulation. TDEE (Total Daily Energy Expenditure) multiplies BMR by a physical activity level factor (PAL). With your TDEE established, you can set a calorie target: a daily deficit of around 500 kcal typically results in about 0.5 kg of weight loss per week, while a surplus supports muscle and weight gain. Macronutrients — protein, carbohydrates and fat — determine body composition and energy levels. Protein intake of roughly 1.6–2.2 g per kg of body weight per day supports muscle maintenance and recovery in active individuals. Hydration matters equally: a common guideline is 30–35 ml of water per kg of body weight per day, with higher needs during exercise and hot weather. Body fat percentage is a more precise measure of body composition than BMI. Calculators based on the U.S. Navy tape-measure method or other anthropometric formulas provide reliable estimates without expensive testing. All health calculators on Liczbnik use established scientific formulas including Mifflin-St Jeor, WHO and the U.S. Navy method. Results are for informational purposes only and do not constitute medical advice. Always consult a doctor or registered dietitian for personal health, diet and fitness decisions.

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Frequently asked questions

How do I calculate BMI?

BMI = weight (kg) / height² (m). E.g. 70 kg and 175 cm: BMI = 22.86 — normal.

How many calories do I need per day?

It depends on weight, height, age, sex and activity. Use the BMR/TDEE calculator.

What is the difference between BMR and TDEE?

BMR is the resting metabolic rate; TDEE = BMR × activity factor — total daily requirement.

WHO: underweight < 18.5; normal 18.5–24.9; overweight 25–29.9; obese ≥ 30.

BMI does not account for body composition — an athlete with high muscle mass may have a high BMI.

Use the TDEE calculator: BMR × PAL. PAL = 1.2 (sedentary) to 1.9 (very active).

No — results are for healthy adults. Consult a doctor for medical conditions.

A deficit of about 500 kcal/day below TDEE yields about 0.5 kg/week loss. Never go below BMR.

No — children have different norms (growth charts). Calculators are for adults.

Absolutely not — they are indicative. Always consult a doctor for health matters.