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Using the Calories Calculator
Understanding your energy expenditure is the cornerstone of any fitness journey. This calories calculator uses the Mifflin-St Jeor equation, widely regarded as the most accurate formula for estimating Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE). By providing your basic biometric data, you can pinpoint exactly how much energy your body needs to maintain its current weight, lose fat, or build muscle.
Whether you are an athlete looking to optimize performance or someone just starting their weight loss journey, knowing your daily caloric "budget" allows you to make informed decisions about your nutrition.
- Age (Years)
- Metabolism naturally slows down with age due to muscle mass loss and hormonal changes. Entering an accurate age helps the formula adjust for these biological shifts.
- Gender
- Biological men generally have a higher percentage of lean muscle mass, which burns more energy at rest than fat. The calculator uses specific constants to account for these physiological differences.
- Weight and Height
- These measurements define your body size. A larger body requires more energy to function and move through space. Weight is calculated in kilograms and height in centimeters for maximum precision.
- Activity Level
- This is a multiplier that accounts for non-resting energy expenditure. This includes everything from fidgeting (NEAT) to intense cardiovascular exercise.
How the Calculation Works
The calories calculator functions in two distinct phases: determining your BMR and then applying your activity multiplier to find your TDEE.
The formulas for Basal Metabolic Rate are:
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
Once the BMR (the energy you burn while lying in bed all day doing nothing) is established, we multiply it by your activity factor:
- Sedentary (1.2): Minimal movement, typical desk job life.
- Lightly Active (1.375): Casual walks or light exercise 1–3 times a week.
- Moderately Active (1.55): Consistent exercise or sports 3–5 days a week.
- Very Active (1.725): High-intensity training 6–7 days a week.
- Extra Active (1.9): Professional athletes or physically demanding manual labor jobs.
Calculation Example
Example Scenario: Let's calculate for a 30-year-old male who weighs 80kg, is 180cm tall, and exercises moderately.
Step-by-step solution:
- Weight = 80, Height = 180, Age = 30
- BMR = (10 × 80) + (6.25 × 180) – (5 × 30) + 5
- BMR = 800 + 1125 – 150 + 5 = 1,780 calories
- TDEE (Moderate) = 1,780 × 1.55
- Maintenance Result = 2,759 calories/day
- Weight Loss Goal (-0.5kg/week) = 2,759 – 500 = 2,259 calories/day
Common Questions
How many calories should I eat to lose weight?
To lose weight, you must create a caloric deficit. A standard recommendation is to reduce your maintenance calories by 500 per day to lose roughly 0.5kg (1 lb) per week. However, never drop below 1,200 (women) or 1,500 (men) calories without medical supervision.
Is the calories calculator 100% accurate?
No calculator can be perfectly accurate because it cannot measure your specific body composition (muscle vs. fat ratio) or metabolic health. It is an estimate. Use it as a starting point and adjust your intake based on your actual weight trends over 2–4 weeks.
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the energy your body needs to keep your organs functioning while at rest. TDEE (Total Daily Energy Expenditure) is your BMR plus all the energy used for movement, digestion, and exercise. TDEE is the number you should use for weight management planning.