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Health & Fitness Calculators

BMI, BMR, TDEE, calorie, macro, body fat, ideal weight, and water intake calculators to help you track fitness goals and maintain a healthy lifestyle.

These calculators estimate key health and fitness numbers: daily calorie needs, body composition, hydration targets, and more. Each result includes the formula used and the medical or scientific reference behind it. These tools are for informational purposes and are not a substitute for professional medical advice.

11 calculators available

Which health calculator do you need?

If you want to know how many calories to eat per day, start with the TDEE calculator. It estimates your Total Daily Energy Expenditure based on your age, weight, height, and activity level using the Mifflin-St Jeor equation. From there, the calorie calculator adjusts for weight loss, maintenance, or gain goals, and the macro calculator splits those calories into protein, carbs, and fat targets.

For body composition, the BMI calculator gives a quick screening number, while the body fat calculator uses body measurements for a more detailed estimate. The ideal weight calculator shows ranges from four established formulas (Devine, Robinson, Miller, and Hamwi) so you can compare them.

Common questions about health calculations

What is the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest, just to keep you alive. TDEE (Total Daily Energy Expenditure) multiplies your BMR by an activity factor to account for exercise and daily movement. For most people, TDEE is 1.4x to 1.9x their BMR. TDEE is the more useful number for meal planning because it reflects what you actually burn in a day.

Is BMI an accurate measure of health?

BMI is a screening tool, not a diagnosis. It uses height and weight to estimate whether you fall into underweight, normal, overweight, or obese categories, but it does not account for muscle mass, bone density, or where you carry fat. Athletes and muscular individuals often have a high BMI despite being healthy. For a more complete picture, pair BMI with a body fat percentage estimate and consult your doctor.

How much water should I drink per day?

A common baseline is half your body weight (in pounds) in ounces. A 160 lb person would aim for about 80 oz (2.4 liters). Activity level, climate, and altitude increase that number. The water intake calculator adjusts for these factors and gives you a personalized daily target based on guidelines from the National Academies of Sciences.