Free Calorie Calculator

About This Tool

Knowing how many calories your body needs each day is the foundation of any effective nutrition plan. Too many calories leads to weight gain; too few can cause muscle loss, fatigue, and nutrient deficiencies. This calorie calculator uses the Mifflin-St Jeor equation, which research published in the Journal of the American Dietetic Association identified as the most accurate predictive equation for estimating resting metabolic rate in both normal-weight and obese individuals. Enter your age, gender, height, weight, activity level, and weight goal to get a personalized estimate of your daily caloric needs. The calculator provides three key numbers: your Basal Metabolic Rate (BMR), which is the energy your body burns at complete rest; your Total Daily Energy Expenditure (TDEE), which factors in physical activity; and your goal-adjusted calorie target for weight loss, maintenance, or gain. You also get a suggested macronutrient breakdown showing how many grams of protein, carbohydrates, and fat to consume daily. The activity multiplier is a critical component of the calculation. A sedentary office worker and an active construction worker of the same size and age can have daily calorie needs that differ by over 1,000 calories. Selecting the right activity level ensures your calorie target reflects your actual energy expenditure rather than a generic average. When in doubt, start with a lower activity level and adjust based on real-world results over 2 to 4 weeks.

The Mifflin-St Jeor Equation

Published in 1990 by MD Mifflin and ST St Jeor, this equation replaced the older Harris-Benedict formula as the preferred method for estimating BMR in clinical and nutritional settings. The formulas are:

• Men: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age + 5
• Women: BMR = 10 x weight(kg) + 6.25 x height(cm) - 5 x age - 161

The BMR represents the minimum calories your body requires to maintain basic functions such as breathing, circulation, cell production, and temperature regulation while completely at rest. This accounts for roughly 60 to 75 percent of total daily calorie expenditure in most adults. The remaining energy is burned through physical activity and the thermic effect of food (the energy used to digest, absorb, and process nutrients).

Activity Level Multipliers

After calculating BMR, the result is multiplied by an activity factor to estimate total daily energy expenditure (TDEE):

• Sedentary (1.2): Desk job with little or no structured exercise. Walking less than 4,000 steps per day.
• Lightly Active (1.375): Light exercise 1 to 3 days per week, or a job that involves some walking. Around 5,000 to 7,500 steps per day.
• Moderately Active (1.55): Moderate exercise 3 to 5 days per week. This covers most recreational gym-goers who train 3 to 4 times weekly.
• Active (1.725): Hard exercise 6 to 7 days per week, or a physically demanding job such as construction or warehousing.
• Very Active (1.9): Intense daily training plus a physical job, or two-a-day training sessions. Common among competitive athletes and military personnel.

Most people overestimate their activity level, which leads to consuming more calories than intended. If you exercise 3 times per week for 30 to 45 minutes, "Lightly Active" or "Moderately Active" is likely the appropriate selection.

Understanding Macronutrients

This calculator uses a balanced 30/40/30 macro split (protein/carbohydrates/fat) as a starting point, which works well for most adults pursuing general health and moderate activity:

• Protein (30% of calories, 4 cal/g): Essential for muscle repair, immune function, and satiety. Higher protein intake helps preserve lean mass during calorie deficits and supports recovery from exercise. A common recommendation is 0.7 to 1 gram per pound of body weight for active individuals.
• Carbohydrates (40% of calories, 4 cal/g): The body's preferred fuel source for high-intensity activity and brain function. Sources include grains, fruits, vegetables, and legumes. Quality matters more than quantity: whole grains and fiber-rich sources are preferable to refined sugars.
• Fat (30% of calories, 9 cal/g): Necessary for hormone production, vitamin absorption (A, D, E, K), and cell membrane integrity. Focus on unsaturated fats from sources like olive oil, nuts, avocados, and fatty fish.

These ratios can be adjusted based on individual goals. Endurance athletes may need higher carbohydrate percentages (50 to 60%), while those following a low-carb approach might shift to 40% protein, 20% carbs, and 40% fat.

Setting a Calorie Deficit or Surplus

Weight change is fundamentally driven by the balance between calories consumed and calories burned:

• Lose 1 lb per week: A deficit of approximately 500 calories per day (3,500 calories per week) results in roughly 1 pound of fat loss. This is widely considered a safe and sustainable rate of weight loss.
• Lose 0.5 lb per week: A 250-calorie daily deficit. Better for those who are already lean or want to minimize muscle loss during a cut.
• Gain 0.5 to 1 lb per week: A surplus of 250 to 500 calories per day supports muscle growth when combined with resistance training. Larger surpluses tend to increase fat gain without additional muscle benefit.

The calculator enforces a minimum of 1,200 calories per day regardless of the deficit selected, as intakes below this threshold make it difficult to meet essential nutrient requirements. If your calculated goal falls below 1,200, consider increasing activity rather than further restricting calories.

Frequently Asked Questions