How do I calculate my calorie needs?

Your calorie needs are calculated in two steps: First, your Basal Metabolic Rate (BMR) is determined — the calories your body burns at rest. Then, this is multiplied by an activity factor (PAL) to get your Total Daily Energy Expenditure (TDEE). Our calculator uses the Mifflin-St Jeor formula by default and optionally the Katch-McArdle formula if you know your body fat percentage.

What is the difference between BMR and TDEE?

BMR (Basal Metabolic Rate) is the energy your body needs at complete rest to maintain vital functions like breathing, heartbeat, and cell regeneration. TDEE (Total Daily Energy Expenditure) additionally includes calories burned through movement, exercise, digestion (thermic effect of food), and general activity. For dieting or meal planning, TDEE is the relevant metric.

How many calories do I need to lose weight?

To lose weight, you need to consume fewer calories than your TDEE. A moderate deficit of 500 kcal per day leads to weight loss of about 0.5 kg per week. We recommend never going below your BMR and keeping the deficit between 300-750 kcal daily to lose weight sustainably without muscle loss.

What is the Mifflin-St Jeor formula?

The Mifflin-St Jeor formula is the most commonly recommended equation for calculating BMR today. Developed in 1990, it is considered the most accurate formula for most people. For men: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age(years) + 5. For women: same formula but -161 instead of +5. It accounts for gender, weight, height, and age.

How accurate is a calorie calculator?

Calorie calculators provide a good estimate with approximately 80-90% accuracy for most people. The Mifflin-St Jeor formula has an average deviation of about 10% from actual BMR. Factors like genetics, hormones, medications, and body composition can influence actual needs. If you enter your body fat percentage, the more accurate Katch-McArdle formula is used.

Should I eat below my BMR?

No, you should never eat below your BMR consistently. BMR only covers vital body functions. Calorie intake below BMR can lead to muscle loss, nutrient deficiency, metabolic slowdown, and hormonal imbalances. Our calculator sets a floor of 1,200 kcal. A moderate deficit below TDEE but above BMR is the safe approach.

How much protein do I need per day?

We recommend 1.8 g protein per kilogram of body weight per day. For muscle building (goal: gain weight), we increase the recommendation to 2.0 g/kg. Protein is crucial for muscle maintenance, satiety, and the thermic effect of food. At 75 kg body weight, that means 135 g protein daily — about 540 kcal from protein alone.

How often should I recalculate my calorie needs?

You should recalculate every 4-6 weeks, especially if your weight has changed by more than 2-3 kg, you've changed your training program, or you've hit a plateau. As body weight decreases, your BMR also decreases, so you need fewer calories than at the start of your diet.

Are 1,200 calories per day enough?

1,200 kcal per day is the absolute minimum and only suitable for very small, light, and inactive individuals. For most people, this intake is too low and can lead to nutrient deficiencies. Women should consume at least 1,400-1,600 kcal and men at least 1,600-1,800 kcal daily. Our calculator considers your individual measurements and never sets an extreme deficit.

How does exercise affect my calorie needs?

Exercise significantly increases your TDEE. Depending on activity level, your BMR is multiplied by a PAL factor: Sedentary (1.2), Lightly active (1.375), Moderately active (1.55), Very active (1.725), Extremely active (1.9). Additionally, our calculator accounts for daily steps: above 7,000 steps, you get a bonus of 0.04 kcal per extra step. This accurately captures everyday movement too.

BMR Formulas Compared: Mifflin-St Jeor vs. Harris-Benedict vs. Katch-McArdle | Calorie Calculator

BMR Formulas Compared: Which Is the Most Accurate?

Choosing the right formula for calculating your Basal Metabolic Rate can make the difference between successful and frustrating meal planning. In this article, we compare the three most important formulas -- Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle -- with concrete calculation examples.

The History of BMR Formulas

Calculating human energy expenditure has a long history. The oldest formula still in use today comes from Harris and Benedict in 1919. Since then, scientists have repeatedly tried to develop more accurate models. The Mifflin-St Jeor formula from 1990 is today's standard, while the Katch-McArdle formula from 1996 represents the most accurate option for athletes.

Mifflin-St Jeor in Detail

The Mifflin-St Jeor formula considers four variables: weight (kg), height (cm), age (years), and gender. For men: BMR = 10 x weight + 6.25 x height - 5 x age + 5. For women: BMR = 10 x weight + 6.25 x height - 5 x age - 161. The formula was validated on a group of 498 individuals with normal to overweight BMI and showed an average deviation of only 5%.

Harris-Benedict: The Classic

The Harris-Benedict formula was developed in 1919 and revised by Roza and Shizgal in 1984. For men: BMR = 88.362 + 13.397 x weight + 4.799 x height - 5.677 x age. For women: BMR = 447.593 + 9.247 x weight + 3.098 x height - 4.330 x age. It tends to overestimate BMR by 5-15%, particularly in overweight individuals.

Katch-McArdle: Best Choice for Athletes

The Katch-McArdle formula is unique because it uses lean body mass (LBM) instead of total weight: BMR = 370 + 21.6 x LBM(kg). The great advantage: it accounts for body composition. A 90 kg bodybuilder with 10% body fat has a completely different BMR than a 90 kg person with 35% body fat. The downside: you need to know or estimate your body fat percentage.

Calculation Example: Male, 30 years, 80 kg, 180 cm

Mifflin-St Jeor: 10 x 80 + 6.25 x 180 - 5 x 30 + 5 = 800 + 1,125 - 150 + 5 = 1,780 kcal

Harris-Benedict: 88.362 + 13.397 x 80 + 4.799 x 180 - 5.677 x 30 = 88 + 1,072 + 864 - 170 = 1,854 kcal

Katch-McArdle (at 15% BF): LBM = 80 x 0.85 = 68 kg. BMR = 370 + 21.6 x 68 = 1,839 kcal

Calculation Example: Female, 25 years, 65 kg, 168 cm

Mifflin-St Jeor: 10 x 65 + 6.25 x 168 - 5 x 25 - 161 = 650 + 1,050 - 125 - 161 = 1,414 kcal

Harris-Benedict: 447.593 + 9.247 x 65 + 3.098 x 168 - 4.330 x 25 = 448 + 601 + 520 - 108 = 1,461 kcal

Katch-McArdle (at 24% BF): LBM = 65 x 0.76 = 49.4 kg. BMR = 370 + 21.6 x 49.4 = 1,437 kcal

Which Formula Should You Use?

For most people, we recommend the **Mifflin-St Jeor formula** as the default. It is easy to apply and delivers solid results. If you know your body fat percentage (e.g., from a body fat scale, caliper measurement, or DEXA scan), the **Katch-McArdle formula** provides more precise results. The Harris-Benedict formula serves well as a comparison value.

Limitations of All Formulas

No formula is perfect. Genetic differences in metabolism, thyroid function, medications, and other factors can cause actual BMR to deviate 10-15% from the estimate. The formulas are a good starting point, but ultimately calorie intake must be fine-tuned based on your body's response.

Conclusion

The choice of formula matters less than consistent application. All three formulas deliver values that typically differ by less than 10%. What matters most is using your calculated value as a starting point and comparing it against your actual weight trends over 2-4 weeks.