Estimated Energy Requirement Calculator & Formula

This calculator estimates your Total Energy Expenditure (TEE) — the number of calories you burn per day — using the standard Mifflin-St Jeor equation and an activity multiplier. You enter your age, sex, height, weight, and typical activity level, and it returns your estimated daily calorie needs for weight maintenance, along with your Basal Metabolic Rate (BMR).

Formula

The calculator uses the Mifflin-St Jeor equation to find your Basal Metabolic Rate (BMR), then multiplies it by an activity factor:

BMR (men) = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5

BMR (women) = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

Estimated Energy Requirement (EER) = BMR × Activity Factor

• weight — body mass in kilograms (1 kg = 2.2 lb)
• height — stature in centimeters (1 inch = 2.54 cm)
• age — in years
• Activity Factor — 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (active), 1.9 (very active)

The result is in kilocalories per day (kcal/day), which is the standard unit for food energy (what people commonly call “calories”).

Worked Example

Using the default inputs: a 30-year-old man, 175 cm tall, 70 kg, with a moderate activity level.

1. Calculate BMR: (10 × 70) + (6.25 × 175) − (5 × 30) + 5 = 700 + 1093.75 − 150 + 5 = 1648.75 kcal/day
2. Apply the moderate activity factor of 1.55: 1648.75 × 1.55 = 2555.56 kcal/day
3. Rounded to the nearest whole number: 2556 kcal/day

This matches the calculator’s output. The BMR line shows 1649 kcal/day, meaning this person burns about 1649 calories at complete rest, and about 2556 calories with moderate daily activity.

What the Result Means

The Estimated Energy Requirement is the number of calories you need to consume to maintain your current body weight, given your activity level. If you eat this amount daily, your weight should stay roughly stable. To lose weight, you need a calorie deficit (eat less or move more); to gain weight, a surplus.

It’s important to understand that this is an estimate, not a precise measurement. Individual metabolism varies by muscle mass, genetics, hormones, and even sleep quality. The true number for any person can differ by 10–20% from the formula’s prediction.

How to Choose Your Activity Level

Choosing the right activity factor is the single biggest source of error. Be honest with yourself — most people overestimate their activity.

• Sedentary (1.2) — desk job, no exercise, mostly sitting all day
• Light (1.375) — desk job plus light exercise 1–3 days per week
• Moderate (1.55) — standing job or moderate exercise 3–5 days per week
• Active (1.725) — physical job or hard exercise 6–7 days per week
• Very Active (1.9) — intense training twice daily, or heavy manual labor

If you’re unsure, choose the lower option. A 30-minute brisk walk is “light” exercise, not “moderate.” The difference between adjacent levels is roughly 200–300 calories per day — enough to account for a pound of weight change every two weeks.

Common Mistakes and Limits

The most frequent errors are unit mix-ups. The formula requires kilograms and centimeters. If you measure in pounds and inches, convert first: weight in lb ÷ 2.2 = kg; height in inches × 2.54 = cm. Entering pounds as kilograms will overestimate your needs by more than double.

Another common error is using the BMR as your total needs. BMR is what you burn at complete rest — before any activity, digestion, or daily movement. Your total needs are always higher unless you are bedridden.

This formula is less accurate for certain groups:

• Very muscular people — the equation underestimates their needs
• Older adults — metabolism slows with age, and the formula may overestimate
• Pregnant or breastfeeding women — needs are higher than the formula predicts
• People with certain medical conditions — thyroid disorders, for example, change metabolism

The Mifflin-St Jeor equation was developed in 1990 and is widely considered the most accurate predictive formula for healthy adults. It replaced the older Harris-Benedict equation, which tends to overestimate by about 5%.

How This Differs From Other Calculators

There are several other equations you might encounter online. The Harris-Benedict equation (revised in 1984) uses different coefficients and typically gives results about 5% higher than Mifflin-St Jeor. The Katch-McArdle formula uses lean body mass instead of total weight, making it more accurate for athletes but requiring a body fat measurement. The WHO/FAO equations are used mainly in clinical settings.

For most people, Mifflin-St Jeor is the best choice. It was validated against direct measurements of energy expenditure and is the recommended equation from the Academy of Nutrition and Dietetics. The difference between equations is usually less than 100–150 calories per day, which is within the margin of error of any predictive method.

Using the Result Safely

This calculator is an educational tool, not medical advice. If you are managing a medical condition, are pregnant, breastfeeding, or under a doctor’s care, consult a healthcare professional before changing your diet.

For weight loss, a deficit of 500–1000 calories per day is commonly cited as producing about 0.5–1 kg (1–2 lb) of weight loss per week. However, extreme deficits below 1200 kcal/day for women or 1500 kcal/day for men can lead to nutrient deficiencies and muscle loss. For weight gain, a surplus of 300–500 calories per day is typical for gradual, lean gains.

Remember that the number on the scale reflects water, glycogen, and food in the digestive tract, not just fat. Track your weight over 2–3 weeks and adjust your intake by 100–200 calories based on the trend, not any single day.

Frequently Asked Questions

What is the difference between BMR and EER?

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to keep your heart beating, lungs breathing, and cells functioning. EER (Estimated Energy Requirement) adds in all your daily activity, from walking to the car to formal exercise. EER is always higher than BMR unless you are completely immobile.

Is the Mifflin-St Jeor formula accurate?

It is the most accurate predictive equation for healthy adults, with an error of about ±10% for most individuals. That means if the calculator says 2500 calories, your true needs are likely between 2250 and 2750. For precise measurement, you would need indirect calorimetry, which measures oxygen consumption and carbon dioxide production in a clinical setting.

Should I eat back the calories I burn from exercise?

Not necessarily. If you are trying to lose weight, the activity factor already accounts for your exercise. Eating back exercise calories on top of that often cancels out your deficit. If you are trying to maintain weight, you can eat back exercise calories, but most people overestimate how many they burn — a 30-minute run burns roughly 300 calories, not 600.

Why does the calculator ask for sex?

Men and women have different average body compositions — men typically have more muscle mass, which burns more calories at rest. The equation accounts for this with a +5 adjustment for men and −161 for women. If you are transgender or on hormone therapy, your metabolism may fall between these values; use the one that matches your current body composition.

How often should I recalculate?

Recalculate whenever your weight changes by more than 5 kg (11 lb), your activity level changes significantly, or you have a major life event like pregnancy. For gradual changes, updating every 3–6 months is sufficient. Your calorie needs decrease slightly as you lose weight because a smaller body requires less energy to maintain.

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in age | Age | years | 30 | 18
in sex | Sex | Male=5, Female=-161 | 5 | 0
in weight | Weight | kg | 70 | 30
in height | Height | cm | 175 | 120
sel activity | Activity Level | Sedentary=1.2, Light=1.375, Moderate=1.55, Active=1.725, Very Active=1.9
out eer | Estimated Energy Requirement | kcal/day | ((10 * weight) + (6.25 * height) - (5 * age) + sex) * activity | 0
out bmr | Basal Metabolic Rate | kcal/day | (10 * weight) + (6.25 * height) - (5 * age) + sex | 0