Calorie Calculator - Calculate Daily Calories Online Free

What Is a Calorie Calculator?

A calorie calculator is a tool that estimates the number of calories your body needs each day to maintain your current weight, lose weight, or gain weight. It works by first calculating your Basal Metabolic Rate (BMR) — the number of calories your body burns at complete rest just to keep you alive — and then multiplying that number by an activity factor to determine your Total Daily Energy Expenditure (TDEE). Your TDEE is the actual number of calories you burn in a typical day, including all daily movement and exercise.

Knowing your daily calorie needs is the foundation of any effective nutrition plan. Whether your goal is to lose fat, build muscle, maintain your current physique, or simply understand your body better, an accurate calorie estimate gives you a clear starting point. This calculator uses the Mifflin-St Jeor equation, which multiple studies have shown to be the most accurate BMR prediction formula for healthy adults.

BMR vs TDEE: Understanding the Difference

Two terms appear frequently in calorie discussions, and understanding the difference between them is essential for setting realistic nutrition goals.

Basal Metabolic Rate (BMR) is the number of calories your body requires to perform basic life-sustaining functions while at complete rest. These functions include breathing, circulating blood, producing hormones, cell repair, and maintaining body temperature. BMR typically accounts for 60 to 75 percent of your total daily calorie expenditure. It is the energy your body would burn if you lay in bed all day doing absolutely nothing.

Total Daily Energy Expenditure (TDEE) is your BMR plus all the additional calories burned through daily activities, exercise, digestion, and movement. TDEE is the number that matters most for practical diet planning because it reflects how many calories you actually burn in a real day. To calculate TDEE, you multiply your BMR by an activity factor that corresponds to your typical exercise level.

For example, a person with a BMR of 1,600 calories who exercises moderately three to five times per week would have a TDEE of approximately 2,480 calories (1,600 × 1.55). This person would need to eat roughly 2,480 calories per day to maintain their current weight.

The Mifflin-St Jeor Formula

The Mifflin-St Jeor equation was published in 1990 by Dr. Michael Mifflin and Dr. St Jeor and has since been validated as the most accurate BMR prediction equation for healthy adults by the American Dietetic Association. The formulas are:

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

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

The formula accounts for the fact that men generally have more lean muscle mass than women, which is reflected in the +5 constant for men versus −161 for women. As you age, your BMR decreases because of the natural loss of lean body mass. Similarly, taller and heavier individuals have higher BMRs because maintaining a larger body requires more energy.

Once BMR is calculated, the tool multiplies it by an activity factor to determine TDEE. This multiplier ranges from 1.2 for sedentary individuals to 1.9 for those who engage in extremely intense daily exercise or have physically demanding occupations.

Activity Levels Explained

The activity multiplier you select significantly impacts your calorie estimate. Here is what each level means:

• Sedentary (1.2) — Desk job with little or no formal exercise. You spend most of the day sitting and only walk for short errands or household tasks.
• Lightly Active (1.375) — Light exercise or sports one to three days per week. This might include walking, yoga, or casual cycling a few times a week.
• Moderately Active (1.55) — Moderate exercise or sports three to five days per week. This includes gym sessions, jogging, swimming, or team sports on a regular schedule.
• Very Active (1.725) — Hard exercise or physical job six to seven days per week. This includes intense training sessions, heavy manual labor, or athletic training programs.
• Extra Active (1.9) — Very hard exercise, physical job, and training twice per day. This level applies to competitive athletes, military personnel, or those with extremely demanding physical occupations.

If you are unsure which level applies to you, err on the side of the lower category. It is better to start with a conservative estimate and adjust upward based on actual results than to overestimate your calorie needs and accidentally eat too much.

Metric vs US Units

This calculator supports both measurement systems so you can enter your data in the units you are most familiar with:

• Metric system — Weight in kilograms (kg), height in centimeters (cm). Used by most countries worldwide and in scientific research.
• US Imperial system — Weight in pounds (lbs), height in feet and inches (ft/in). Common in the United States and a few other countries.

The internal calculation always converts to metric before applying the formula, ensuring consistent and accurate results regardless of which unit system you choose. No manual conversion is needed on your part.

Use Cases for Calorie Calculation

Weight Loss

To lose weight, you need to consume fewer calories than your TDEE. A deficit of 500 calories per day results in approximately one pound of weight loss per week, since one pound of body fat contains roughly 3,500 calories. For sustainable results, aim for a moderate deficit of 300 to 500 calories rather than an aggressive restriction that can slow your metabolism and lead to muscle loss.

Muscle Gain

Building muscle requires a caloric surplus to provide the energy needed for muscle repair and growth. A modest surplus of 200 to 300 calories above your TDEE, combined with a structured strength training program, supports lean mass gains while minimizing excess fat accumulation. Consuming too large a surplus leads to unnecessary fat gain that is difficult to lose later.

Weight Maintenance

Once you reach your target weight, eating at your TDEE level helps you maintain that weight. This is where many people struggle after a diet ends. Understanding your maintenance calories allows you to transition from a deficit to a stable intake without regaining the weight you worked hard to lose.

Diet Planning

Whether you follow a specific dietary approach or simply want to make more informed food choices, knowing your calorie target is the first step. From there, you can distribute calories across macronutrients (protein, carbohydrates, and fat) to match your goals and preferences. Use our Percentage Calculator to split your daily calories into macro percentages.

Limitations of Calorie Formulas

While the Mifflin-St Jeor equation is the most accurate population-level formula available, it is still an estimate. Individual metabolism can vary by 10 to 15 percent from the predicted value due to genetics, body composition, hormonal factors, and other variables that no simple formula can capture. Muscle tissue burns more calories at rest than fat tissue, so two people of the same weight and height may have different actual BMRs depending on their muscle-to-fat ratio.

For the most accurate results, use the calculator output as a starting point, track your actual weight and calorie intake for two to three weeks, and adjust your target based on real-world results. If you are losing weight faster than expected, increase your intake slightly. If you are not losing weight, decrease it by 100 to 200 calories and reassess.

How to Use This Tool

1. Select your unit system — Choose Metric (kg, cm) or US Imperial (lbs, ft/in) for height and weight inputs.
2. Enter your details — Input your age, gender, height, and weight. These are used to calculate your BMR via the Mifflin-St Jeor equation.
3. Choose your activity level — Select the option that best matches your typical weekly exercise and movement patterns.
4. View your results — See your BMR, maintenance calories, and recommended targets for weight loss, weight gain, and muscle building.

Want to understand your total daily energy expenditure in more detail? Try our TDEE Calculator for a breakdown of how different activity levels affect your calorie needs.

Related Tools

• TDEE Calculator — Calculate your Total Daily Energy Expenditure with a detailed activity breakdown.
• Percentage Calculator — Split your daily calories into macronutrient percentages for a structured meal plan.

Privacy

All calorie calculations are performed entirely in your browser using JavaScript. No personal data, body measurements, or calculation results are sent to our servers. The tool processes your inputs locally and discards them as soon as you navigate away from the page. No cookies or tracking scripts collect your health information.