Tinker Tools

Calorie Calculator Instantly

Calculate your daily calorie needs using the Mifflin-St Jeor equation. Get BMR, TDEE, and goal-based calorie targets with macronutrient guidance.

ResultMifflin-St Jeor Equation

Enter your details and click Calculate Calories.

How it works

1. Enter Your Details

Provide your age, gender, height (cm), and weight (kg). Select your activity level from five options ranging from sedentary to very active.

Personal Data

2. Get BMR & TDEE

Your Basal Metabolic Rate is calculated using the Mifflin-St Jeor equation. Multiply by your activity factor to get Total Daily Energy Expenditure.

Science-Based

3. Plan Your Nutrition

Review calorie targets for weight loss, maintenance, or gain. Use the macronutrient guide to plan your protein, carbs, and fat intake.

Goal-Based

What is a Calorie Calculator?

A calorie calculator estimates the number of calories your body needs each day to maintain, lose, or gain weight. The core idea rests on a concept called Total Daily Energy Expenditure — TDEE. Your TDEE represents every calorie your body burns in a 24-hour period, from the energy required to keep your heart beating and lungs breathing to the calories you torch during a morning jog or an afternoon of yard work. When you eat fewer calories than your TDEE, your body taps into stored energy and you lose weight. Eat more than your TDEE and the surplus gets stored — primarily as body fat. That energy balance equation is the single most reliable predictor of body weight changes over time, and a calorie calculator puts the math at your fingertips.

The foundation of any TDEE estimate is your Basal Metabolic Rate — BMR. This is the number of calories your body would burn if you did absolutely nothing all day. Think of it as the cost of simply being alive: your organs functioning, your cells dividing, your body temperature holding steady at roughly 37 degrees Celsius. BMR typically accounts for 60 to 75 percent of total daily calorie expenditure. The remaining calories come from physical activity and the thermic effect of food — the energy your body spends digesting and absorbing nutrients. Two well-established formulas exist for estimating BMR: the Harris-Benedict equation and the Mifflin-St Jeor equation. Each takes your age, sex, height, and weight as inputs, yet they produce slightly different results due to differences in the study populations on which they were developed.

Once you know your BMR, the calculator multiplies it by an activity factor to arrive at your TDEE. A sedentary office worker and a construction laborer with identical BMRs will have vastly different TDEEs because physical activity adds a significant calorie cost on top of baseline metabolism. From there, you can adjust your daily intake upward or downward depending on your goal — whether that is fat loss, muscle gain, or simply maintaining your current body composition. The calculator does not prescribe a diet. It gives you a number to work with, and what you do with that number is up to you.

Key Features and Benefits

  • Dual BMR Formulas — Choose between the revised Harris-Benedict equation (Roza and Shizgal, 1984) and the Mifflin-St Jeor equation (1990). Research published in the Journal of the American Dietetic Association found Mifflin-St Jeor to be the most accurate for non-obese individuals, while Harris-Benedict remains widely cited in clinical settings. Having both options lets you compare results and pick the estimate that best fits your profile.
  • Activity Level Multipliers — Select from five activity tiers — sedentary (x1.2), lightly active (x1.375), moderately active (x1.55), very active (x1.725), and extra active (x1.9). These multipliers come from research on the energy costs of different lifestyles. Picking the right tier is the single biggest source of variation in your TDEE estimate, so the calculator includes descriptions and examples for each level to guide your choice.
  • Goal-Based Adjustments — After computing your maintenance TDEE, the calculator shows you adjusted calorie targets for common goals. A moderate deficit of 500 calories per day translates to roughly 0.45 kg of fat loss per week. A surplus of 250 to 500 calories supports lean muscle gain when paired with resistance training. You see the numbers for each scenario side by side.
  • Macronutrient Breakdown — Calories tell you how much to eat. Macronutrients — protein, carbohydrates, and fat — tell you what to eat. The calculator offers suggested macro splits based on your goal. A fat-loss plan might allocate 40 percent of calories to protein, 30 percent to carbs, and 30 percent to fat. A muscle-building plan shifts those ratios. You get gram targets, not just percentages, because grams are what you actually measure in a kitchen.
  • Metric and Imperial Input — Enter your height in centimeters or feet and inches. Enter your weight in kilograms or pounds. The calculator handles conversions silently so you never need to reach for a unit converter before you start.
  • Privacy-First Processing — Every calculation runs in your browser. Your age, weight, height, and activity data stay on your device. Nothing is transmitted to a server, stored in a database, or used for advertising purposes.

How to Calculate Your Daily Calorie Needs

  1. 1

    Gather Your Measurements

    You need four pieces of information: your current weight, your height, your age, and your biological sex. Weigh yourself in the morning before eating, wearing minimal clothing, on a hard flat surface. Measure your height barefoot against a wall. Record your age in years. Biological sex matters here because men and women differ in average body composition — men tend to carry more muscle mass, which raises BMR. If you measured in imperial units, the calculator will convert internally. Accuracy at this stage directly affects the quality of the final estimate, so take the time to measure carefully rather than guessing.

  2. 2

    Select Your BMR Formula

    The Mifflin-St Jeor equation for men is BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5. For women, replace the +5 with -161. The revised Harris-Benedict equation for men is BMR = (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age in years) + 88.362. For women it is BMR = (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age in years) + 447.593. Both formulas are well-validated, but Mifflin-St Jeor was developed on a more recent population sample and tends to produce slightly lower — and often more accurate — estimates for people of typical body composition.

  3. 3

    Choose Your Activity Level

    This step introduces the most subjective variable in the entire calculation. Sedentary means you work a desk job and do little to no exercise. Lightly active means you exercise one to three days per week at a moderate intensity. Moderately active covers three to five days of exercise per week. Very active means six to seven days of hard exercise or a physically demanding job. Extra active applies to athletes in heavy training or people with extremely physical occupations like manual laborers who also exercise. Most people overestimate their activity level. If you are unsure, err on the conservative side — you can always adjust upward after tracking your weight for two to three weeks.

  4. 4

    Review Your TDEE

    The calculator multiplies your BMR by the activity multiplier you selected. The result is your estimated TDEE — the number of calories you would need to eat each day to maintain your current weight, assuming your activity level stays consistent. A 30-year-old man who is 175 cm tall, weighs 75 kg, and exercises moderately might see a TDEE around 2,500 calories. A 25-year-old woman who is 163 cm tall, weighs 58 kg, and is lightly active might land near 1,750 calories. These are estimates, not certainties. Individual variation in metabolism, gut microbiome composition, non-exercise activity thermogenesis, and hormonal status means your true TDEE could differ by 10 to 15 percent in either direction.

  5. 5

    Set Your Calorie Target

    If your goal is weight loss, subtract 300 to 500 calories from your TDEE. A deficit of 500 calories per day produces about 0.45 kg of fat loss per week — a rate that research consistently supports as sustainable and safe. Deficits larger than 750 calories per day increase the risk of muscle loss, nutrient deficiencies, and metabolic adaptation. If your goal is muscle gain, add 250 to 500 calories above your TDEE. Larger surpluses accelerate fat gain more than they accelerate muscle growth. If you want to maintain weight, eat at your TDEE and monitor the scale over two to four weeks to confirm the estimate is accurate.

  6. 6

    Distribute Your Macronutrients

    Protein should be the anchor of your macro plan. A target of 1.6 to 2.2 grams per kilogram of body weight per day is well-supported by sports nutrition research for anyone who exercises regularly. Each gram of protein provides 4 calories. After allocating protein calories, divide the remaining calories between fat and carbohydrates. Fat is essential for hormone production and cell membrane integrity — aim for at least 0.8 grams per kilogram of body weight per day, with each gram providing 9 calories. Fill the remaining calorie budget with carbohydrates at 4 calories per gram. Carbs fuel high-intensity exercise, support brain function, and make meals more enjoyable.

Expert Tips for Accurate Calorie Tracking

No formula can predict your exact calorie needs. The Harris-Benedict and Mifflin-St Jeor equations are regression models built on averages. They work well for most people, but they cannot account for individual differences in thyroid function, sympathetic nervous system activity, or the efficiency of your mitochondria. Treat your calculated TDEE as a starting hypothesis. Eat at that level for two to three weeks, weigh yourself daily under consistent conditions, and average the weekly results. If your weight stays stable, the estimate was accurate. If you gain or lose more than expected, adjust by 100 to 200 calories and retest. This iterative approach — calculate, observe, adjust — is how nutrition coaches dial in calorie targets for their clients.

The thermic effect of food is a variable that most calculators ignore but that can shift your effective calorie balance by 5 to 10 percent. Protein has the highest thermic effect — your body uses roughly 20 to 30 percent of the calories in protein just to digest and absorb it. Carbohydrates cost about 5 to 10 percent, and fats cost only 0 to 3 percent. This is one reason high-protein diets tend to produce slightly better fat-loss results even at the same total calorie intake. The effect is already partially captured in population-based TDEE formulas, but it explains why two diets with identical calorie counts but different macro ratios can produce different outcomes on the scale.

Calorie counting has known psychological pitfalls. Some people develop an unhealthy obsession with numbers, leading to disordered eating patterns. If tracking every meal causes you anxiety, consider a less granular approach — such as portion control using hand-size estimates or the plate method, where half your plate is vegetables, a quarter is protein, and a quarter is starchy carbs. These heuristic methods are less precise but psychologically sustainable for many people. The best dietary strategy is the one you can follow consistently over months and years, not the one that looks perfect on a spreadsheet for two weeks before you abandon it.

Non-exercise activity thermogenesis — NEAT — is the wildcard in your energy balance equation. NEAT includes every calorie you burn through fidgeting, walking to the mailbox, standing at your desk, gesturing while you talk, and performing household chores. Studies have shown that NEAT can vary by as much as 2,000 calories per day between individuals with similar body sizes. When you cut calories, your body often unconsciously reduces NEAT — you fidget less, you sit more, you take the elevator instead of the stairs. This metabolic adaptation is a normal survival mechanism, not a sign that your metabolism is broken. Staying aware of your daily movement outside the gym can help you maintain your calorie deficit without white-knuckling through extreme hunger.

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Your daily calorie needs sit at the intersection of biology, behavior, and goals. The Calorie Calculator gives you a research-backed starting point — but it works best when combined with other tools. Use the BMI Calculator to see how your current weight maps to recognized health categories, or explore the Health Insurance Calculator to understand how weight-related conditions might affect your coverage costs. Each tool adds a dimension that the others miss, and together they help you make more informed decisions about your health and your finances.

Frequently Asked Questions

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