Whether you want to lose weight, gain weight or maintain it, the key piece of information is how many calories your body actually burns each day. The calorie calculator first works out the basal metabolic rate (BMR) using the Harris-Benedict formula, then multiplies it by the PAL factor – your actual activity level. The result is a realistic total energy requirement tailored to you.
Step by Step: How to Use the Calorie Calculator
- Enter sex, age and body data: Input your sex, age in years, height in cm and current weight in kg. These four values feed into the Harris-Benedict formula.
- Choose your activity level (PAL factor): Select your typical activity level: from "mostly sedentary" (PAL 1.2) to "very active with physical work and sport" (PAL 1.9).
- Set your goal: Do you want to maintain weight (calorie intake = requirement), lose weight (deficit of 300–500 kcal) or build muscle (surplus of 200–300 kcal)?
- Read the basal metabolic rate: The calculator shows the BMR – the number of calories the body burns at rest.
- Note the total energy expenditure: The overall requirement (BMR × PAL) is the value you should base your diet on.
Practical Examples
Example 1 – Office worker, 35 years, male, 180 cm, 82 kg: BMR using Harris-Benedict: 88.4 + (13.4 × 82) + (4.8 × 180) − (5.7 × 35) = 88.4 + 1,098.8 + 864 − 199.5 = 1,851.7 kcal. PAL 1.4 (desk work + light sport): 1,851.7 × 1.4 = 2,592 kcal/day total requirement.
Example 2 – Woman, 28 years, 165 cm, 63 kg, dieting: BMR: 447.6 + (9.2 × 63) + (3.1 × 165) − (4.3 × 28) = 447.6 + 579.6 + 511.5 − 120.4 = 1,418.3 kcal. PAL 1.5 (moderate activity): 1,418.3 × 1.5 = 2,127 kcal requirement. For moderate weight loss: 2,127 − 400 = 1,727 kcal/day target.
Example 3 – Endurance athlete in training: 30-year-old triathlete, 75 kg, 178 cm. BMR approx. 1,825 kcal. In training weeks with 2 hours of sport per day: PAL 1.9 → requirement 3,467 kcal. On rest days: PAL 1.4 → 2,555 kcal. This fluctuation explains hunger and energy dips that endurance athletes experience.
Calorie Needs: Harris-Benedict Formula
Men BMR: 88.4 + (13.4 × kg) + (4.8 × cm) − (5.7 × years). Women BMR: 447.6 + (9.2 × kg) + (3.1 × cm) − (4.3 × years). Total energy expenditure: BMR × PAL factor (1.2–1.9).
Frequently Asked Questions (FAQ)
What is the difference between kcal and kJ?
Kilocalories (kcal) and kilojoules (kJ) both measure the energy content of food. 1 kcal = 4.184 kJ. In many countries both values are required on food packaging. Colloquially people say "calories" but always mean kilocalories.
How accurate is the Harris-Benedict formula?
The revised Harris-Benedict formula (and the similar Mifflin-St Jeor equation) is a reliable guide. It tends to underestimate BMR in very muscular individuals and overestimate it in those with obesity. As a reference point with ±10% accuracy, it works well for most adults. For precise measurements, indirect calorimetry is used.
Which PAL factor should I choose if I exercise three times a week?
Three 60-minute moderate exercise sessions per week alongside a predominantly sedentary job corresponds to a PAL of around 1.5–1.6. You can also calculate day by day: office days PAL 1.3; sport days PAL 1.7–1.8. The weekly average gives your realistic overall requirement.
