About Calorie Rule
Calorie Rule is a free, comprehensive fitness and nutrition calculator platform designed to help people make informed decisions about their health and fitness goals. Whether you want to calculate your Total Daily Energy Expenditure (TDEE), determine your Body Mass Index (BMI), plan your macronutrient intake, or track calories burned during exercise, Calorie Rule provides instant, science-backed results with no sign-up required.
What started as a handful of energy calculators is now also a reference library: alongside the TDEE, BMR and macro tools, the site holds 325 food pages, 82 activity pages and 30 exercise guides. No result waits behind an email address, a login or a payment.
Our Mission
The job of the site is narrow: turn a few things you already know about yourself (age, sex, height, weight, how much you move) into a daily energy figure you can act on, and print the arithmetic next to it so you can check it. Losing fat, gaining muscle and holding steady all start from that same estimate of daily expenditure, so that estimate gets the most care.
The 2,000 kcal printed on food labels is a labelling convention, not anyone's personal target. Run the equation for an 85 kg, 25-year-old man who trains five times a week and for a 55 kg, 60-year-old woman who works at a desk, and the two daily figures end up well over 1,000 kcal apart. Making that gap visible is the point of the calculators.
The Problem We Solve
The fitness and nutrition information landscape is notoriously confusing. Conflicting advice, pseudoscience, and commercial interests create a fog of misinformation that makes it difficult for ordinary people to make sound decisions about their health. How many calories should you eat? What macronutrient split should you follow? How many calories did you actually burn during your workout? These are fundamental questions, yet the answers vary wildly depending on who you ask.
Calorie Rule cuts through this noise by applying established, peer-reviewed formulas to provide personalized answers. Our TDEE calculator uses the Mifflin-St Jeor equation, widely regarded as the most accurate formula for estimating resting metabolic rate. Our BMI calculator follows WHO standards. Our macro calculator uses evidence-based ranges for protein, carbohydrate, and fat intake based on activity level and goals. Every calculation on our platform is grounded in published research, not marketing claims.
Our Methodology
Each calculator page names the equation it runs and where its coefficients come from, and the methodology page gathers them in one list. If a result surprises you, the figures printed on the page are enough to redo it by hand.
Our approach to fitness calculations follows several key principles:
- Evidence-Based Formulas: We use only peer-reviewed, clinically validated equations. The Mifflin-St Jeor equation for BMR, the Harris-Benedict equation as a reference point, MET values from the Compendium of Physical Activities, and WHO-standard BMI classifications.
- Personalization: Every calculator takes into account your individual metrics – age, sex, height, weight, activity level, and goals – to deliver results tailored specifically to you, not generic population averages.
- Transparency: We show users the formulas and explain how results are calculated. We believe in educating users, not just giving them numbers. Understanding why your TDEE is a certain value helps you make better decisions about adjusting your intake.
- Practical Guidance: Beyond raw numbers, we provide context and actionable advice. If your BMI falls in the overweight range, we explain what that means and what steps you might consider. If your macro split is 40/30/30, we help you understand what that looks like in actual food choices.
The Mifflin-St Jeor Equation Explained
At the heart of our TDEE and calorie calculators is the Mifflin-St Jeor equation, published in 1990 by Dr. Mark Mifflin and Dr. Sachiko St Jeor. This equation has been validated in numerous clinical studies and is recommended by the Academy of Nutrition and Dietetics as the most reliable formula for estimating Basal Metabolic Rate (BMR) in healthy adults. The equation is as follows:
- For men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5
- For women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161
BMR represents the number of calories your body burns at complete rest to maintain essential physiological functions such as breathing, circulation, cell production, and thermoregulation. It accounts for approximately 60 to 75 percent of total daily energy expenditure in sedentary individuals.
The Mifflin-St Jeor equation replaced the older Harris-Benedict equation (1919) as the gold standard because large-scale validation studies demonstrated that it predicts measured BMR within 10 percent of actual values for the majority of individuals, whereas the Harris-Benedict equation tends to overestimate BMR by 5 to 15 percent, particularly in individuals with overweight or obesity. Our platform uses Mifflin-St Jeor as the primary formula while offering the Harris-Benedict equation as an alternative reference.
Understanding TDEE Calculation
Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a 24-hour period, accounting for all forms of energy expenditure: Basal Metabolic Rate, the thermic effect of food (TEF), non-exercise activity thermogenesis (NEAT), and exercise activity thermogenesis (EAT). TDEE is the most important number for anyone looking to manage their weight, as it represents the caloric balance point – eating above your TDEE leads to weight gain, and eating below it leads to weight loss.
Calorie Rule calculates TDEE by multiplying your BMR by an activity factor that reflects your overall daily movement and exercise habits. These activity multipliers are derived from research published in the American Journal of Clinical Nutrition and range from 1.2 (sedentary, little or no exercise) to 1.9 (extremely active, hard exercise twice daily or physical labour). Users select the activity level that best matches their typical week, and the calculator provides a TDEE estimate along with calorie targets for different goals: weight loss, maintenance, and muscle gain.
Macronutrient Ratios and Nutritional Science
Calories tell you how much to eat, but macronutrient ratios tell you what to eat. The three primary macronutrients – protein, carbohydrates, and fat – each play distinct roles in the body, and the optimal ratio varies based on individual goals, activity level, and metabolic health.
Our macro calculator draws on guidelines published by the International Society of Sports Nutrition (ISSN), the American College of Sports Medicine (ACSM), and the Dietary Guidelines for Americans. For protein, we recommend 1.6 to 2.2 grams per kilogram of bodyweight for individuals engaged in resistance training, based on meta-analyses demonstrating that this range maximises muscle protein synthesis. For fat, we recommend a minimum of 20 percent of total calories to support hormone production, brain function, and absorption of fat-soluble vitamins (A, D, E, K). Carbohydrates fill the remaining caloric budget, with higher ratios recommended for endurance athletes and lower ratios for individuals pursuing fat loss.
Each macronutrient has a specific caloric density: protein provides 4 calories per gram, carbohydrates provide 4 calories per gram, and fat provides 9 calories per gram. These values are used by our calculator to convert your calorie targets into gram amounts for each macronutrient, giving you practical numbers you can use for meal planning and food tracking.
Data Sources and Scientific References
Calorie Rule is committed to scientific rigour. The formulas, recommendations, and nutritional data used throughout our platform are sourced from established authorities in nutrition and exercise science:
- USDA FoodData Central: The primary source for our food nutrition database, providing comprehensive macronutrient and micronutrient data for thousands of food items.
- World Health Organization (WHO): BMI classification standards, global dietary guidelines, and public health recommendations on nutrition and physical activity.
- Compendium of Physical Activities: Published by Ainsworth et al. and maintained by Arizona State University, this database provides MET (Metabolic Equivalent of Task) values for hundreds of physical activities, which we use in our calories burned calculator.
- American College of Sports Medicine (ACSM): Exercise guidelines, recommended activity levels, and position stands on nutrition for athletic performance.
- International Society of Sports Nutrition (ISSN): Evidence-based position stands on protein requirements, meal timing, and supplement efficacy.
- Dietary Guidelines for Americans (DGA): Published jointly by the USDA and HHS, these guidelines inform our general nutrition recommendations and macronutrient range suggestions.
Our Calculators
Calorie Rule offers a comprehensive suite of fitness and nutrition calculators, each designed to address a specific aspect of health and performance planning:
- TDEE Calculator: Calculates your Total Daily Energy Expenditure – the total number of calories you burn per day including exercise and daily activity. This is the starting point for any nutrition plan.
- BMI Calculator: Computes your Body Mass Index based on height and weight, with WHO-standard classification and health context.
- BMR Calculator: Determines your Basal Metabolic Rate – the calories your body burns at complete rest to maintain basic life functions.
- Calorie Calculator: Estimates daily calorie needs based on your goals (lose weight, maintain, gain muscle) with personalized recommendations.
- Macro Calculator: Breaks down your calorie target into optimal protein, carbohydrate, and fat ratios based on your activity level and objectives.
- Calories Burned Calculator: Estimates energy expenditure for hundreds of activities and exercises using MET values from published research.
- Body Fat Calculator: Estimates body fat percentage using the U.S. Navy method, providing a more nuanced view of body composition than BMI alone.
- One Rep Max Calculator: Calculates your estimated one-rep maximum for strength training exercises using the Epley formula.
- Pace Calculator: Helps runners and cyclists calculate pace, speed, and finish times for training and race planning.
- Calorie Deficit Calculator: Determines the optimal calorie deficit for safe, sustainable weight loss based on your current metrics and timeline goals.
Food and Activity Database
Beyond calculators, Calorie Rule maintains a growing database of foods, activities, and exercises. Each food entry includes detailed nutritional information – calories, protein, carbohydrates, fat, and serving size – along with educational content about nutritional benefits and practical uses. Our activity database covers hundreds of exercises and activities with MET values and calorie-burn estimates, helping users understand the energy cost of their daily activities and workouts.
Technology and Performance
Every food, activity and exercise page here was written to disk before anyone asked for it. A Python script reads three data files (foods, activities, exercises), pours them into Jinja2 templates and writes plain HTML; GitHub Actions runs that script on every change and publishes the result on GitHub Pages. The hourly figure on an activity page, for instance, is simply its MET value multiplied by a reference body weight of 70 kg.
The calculators are the only part that reacts to you, and they do it inside the page. One JavaScript file holds the Mifflin-St Jeor, Harris-Benedict and Katch-McArdle equations, the U.S. Navy body-fat formula, the Epley and Brzycki one-rep-max estimates and the burn formula MET × body weight in kg × hours. Your entries feed the arithmetic and are then forgotten; the only thing remembered is whether you prefer metric or imperial units, kept in your browser's localStorage.
Who Publishes Calorie Rule
The site belongs to Radif Partners, a publisher of calculators and practical guides. Radif Partners picks the equations, loads the nutrition and activity figures into the data files and writes the guides, and is answerable for every number shown. No hospital, dietetic association or food brand stands behind the site, which is why each result is presented as an estimate and not as advice.
A page is revised when a reference source changes its values or when a reader points out an error. The date shown at the top of each page is the date of its last real change, read from the site's version history rather than typed by hand.
Privacy and Trust
Weight, height, age and body measurements never leave the calculator: your browser does the sums and sends nothing back. What the site does measure is traffic, with Google Analytics 4 and Microsoft Clarity, to see which pages get read and which need work. The privacy policy lists the cookies those two tools set and how long they last.
Corrections and New Entries
A food or an activity becomes a page the moment it is added to the data files: the next build writes it, with its nutrition table or its MET-based burn figures, and lists it in the sitemap.
Found a calorie count that does not match the USDA entry, or an activity rated at the wrong MET? Send the page address and your source to contact@calorierule.com. Once the figure is checked, the data file is corrected and the page is rebuilt with a new update date.