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BMR & TDEE Calculator: Know Exactly How Many Calories You Need

This free BMR and TDEE calculator estimates your Basal Metabolic Rate — the calories your body burns at complete rest — and your Total Daily Energy Expenditure, the calories you actually need each day once your activity level is factored in. Enter your age, sex, height, and weight in metric or imperial units, select your activity level, and instantly see your BMR, your maintenance calories (TDEE), and ready-made targets for weight loss at three deficit levels, maintenance, and weight gain.

Knowing your daily calorie requirement is the foundation every effective nutrition plan is built on — whether you're cutting, eating at maintenance, or building muscle. This calculator converts four simple inputs into a personalised calorie target backed by peer-reviewed formulas — giving you a number you can actually act on rather than a generic 2,000-calorie default.

Three Proven BMR Formulas: Mifflin-St Jeor, Harris-Benedict & Katch-McArdle

No two bodies are identical, so this tool lets you choose the BMR formula that fits your situation. The Mifflin-St Jeor equation is the modern standard and is widely regarded as the most accurate general-population formula — it's the default, and the one most registered dietitians and sports scientists use. The revised Harris-Benedict equation (1990 version) is a well-established alternative that many people encounter in nutrition courses and textbooks. The Katch-McArdle formula calculates BMR from lean body mass rather than total body weight, making it the most accurate option for muscular athletes and very lean individuals whose needs total-weight formulas tend to underestimate.

Switch between all three formulas and compare the results side by side. For most people, Mifflin-St Jeor is the best starting point. If you know your body-fat percentage — from a DEXA scan, calipers, or the body fat calculator on this site — enter it in the optional field to activate Katch-McArdle for a more personalized BMR estimate.

From BMR to a Real Daily Calorie Target: Deficits, Surpluses, and Macros

Your BMR is the starting point, not the destination. Multiply it by an activity factor — from sedentary (1.2) to extra active (1.9) — to get your TDEE, which is the number of calories that maintains your current weight. Eat below TDEE and you lose fat; eat above and you gain weight. The calculator does this arithmetic automatically and presents it as concrete, actionable calorie targets: mild deficit (−250 kcal), standard deficit (−500 kcal), aggressive deficit (−1000 kcal), maintenance, mild surplus, and bulk.

A deficit of 500 calories per day produces approximately 0.5 kg (about 1 lb) of weight loss per week — a rate most nutritionists consider sustainable without significant muscle loss. The calculator also breaks your calorie target into macronutrient grams, giving you a protein, carbohydrate, and fat framework for meal planning rather than just a single number to stay under. Protein intake of 0.7–1g per pound of body weight is the most evidence-backed lever for preserving lean muscle during a deficit.

Why This TDEE Calculator Beats MyFitnessPal, Cronometer, and Generic Online Tools

MyFitnessPal and Cronometer are excellent food-logging apps but their calorie calculators are basic entry points designed to get you into their tracking ecosystem — you need an account to use them, and neither lets you compare multiple BMR formulas. Generic online TDEE calculators typically offer a single formula with no transparency about which equation they use. IIFYM.com (If It Fits Your Macros) is more detailed but cluttered with ads and affiliate content.

UtiloKit's calculator provides three selectable BMR formulas with side-by-side comparison, a full macro breakdown, calorie targets at every goal level, safety flags for overly aggressive deficits, and an optional body-fat input for Katch-McArdle — all in a clean, ad-free interface that runs entirely in your browser. No account required, no food-logging subscription pushed, no data uploaded. It's the calculation depth of a dietitian's assessment form delivered as an instant, private browser tool.

Privacy: Your Health Data Stays on Your Device

Every calculation in this tool — BMR, TDEE, calorie targets, macro breakdown — runs as client-side JavaScript in your browser. Your age, weight, height, sex, and body-fat percentage are never uploaded to any server, never stored in a database, and never used for advertising profiling. This matters particularly for health data, which many users are rightly reluctant to share with ad-supported platforms.

Unlike MyFitnessPal (acquired by Francisco Partners, then Noom), which ties your health metrics to an account used for ad targeting and research partnerships, UtiloKit has no account system and no data collection. Close the tab and there is no record. Open it again and nothing is pre-filled. The privacy model is simple: your health numbers never leave your device.

BMR & TDEE Calculator on Any Device: Desktop, iPhone, and Android

The calculator is fully responsive and works identically on desktop computers, iPhones, iPads, and Android devices. All input fields are touch-friendly with appropriately sized tap targets for mobile use. The results panels adapt to narrow screens without losing any data. On iPhone, use it in Safari or Chrome without installing anything — it loads once and the JavaScript runs locally, meaning subsequent uses are fast even on slower mobile connections.

On Android, Chrome is recommended, though Firefox and Edge both work perfectly. The tool has no app to download, no notification permissions to grant, and no background data to sync. Bookmark it on your home screen for instant access — it works as a lightweight alternative to full nutrition-tracking apps when all you need is a quick calorie and macro target check.

The Physiology of Basal Metabolic Rate: What Your Body Is Actually Burning

Basal Metabolic Rate is defined precisely: the energy expended by the body at complete rest, in a post-absorptive state (no food consumed for at least 12 hours), in a thermoneutral environment — typically 20–25 °C — lying still and awake. These conditions eliminate the heat generated by digestion, muscle activity, and thermoregulation, leaving only the irreducible minimum energy cost of being alive. That minimum is surprisingly large: for most adults it accounts for 60–70% of all the calories burned each day, far outstripping formal exercise in its contribution to total energy balance.

The distribution of that energy across organs is counterintuitive. The brain, which represents roughly 2% of body weight, consumes approximately 20% of BMR — about 250–350 kcal per day in an adult — because neurons maintain steep electrochemical gradients continuously regardless of whether you are thinking hard or drifting off to sleep. The liver accounts for around 27% of BMR, fuelled by the enormous metabolic work of gluconeogenesis, protein synthesis, detoxification, and bile production. The kidneys (~10%), heart (~7%), and other organs collectively claim another significant share. Skeletal muscle — despite being the largest tissue in the body by mass — contributes only about 18% of BMR at rest, roughly 13 kcal per kilogram per day, a much lower rate per unit of mass than the liver or brain.

It is important to distinguish BMR from the closely related term Resting Metabolic Rate (RMR). RMR is measured under similar but less strict conditions: the subject is resting but not necessarily in a fasted state, making the measurement easier to obtain in a clinical setting. Because digestion and mild residual muscle activity contribute small amounts of heat, RMR runs slightly higher than true BMR — typically by 10–20%. In practice, the two terms are used interchangeably in most nutrition contexts, and the formulas implemented in this calculator are derived from RMR measurements even when labeled as BMR equations. The difference is not clinically meaningful for the purpose of setting a daily calorie target.

The Major BMR Formulas Compared: Mifflin-St Jeor, Harris-Benedict, Katch-McArdle, and Schofield

Four equations dominate BMR estimation in clinical and research practice, each with distinct strengths and limitations. The Mifflin-St Jeor equation (1990) is the current gold standard for general adults. It was derived from measured RMR in 498 men and women across a wide range of ages, heights, and weights, and multiple validation studies confirm it produces the lowest mean prediction error against indirect calorimetry — the gold-standard laboratory method. The formulas are: Men: (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5; Women: (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161. The only meaningful limitation is that it uses total body weight, so it slightly underestimates BMR in very muscular individuals and slightly overestimates it in individuals carrying a large proportion of body fat.

The original Harris-Benedict equation was published in 1919, revised in 1984 by Roza and Shizgal. It was calibrated on a population that was generally leaner than today's adults, causing it to systematically overestimate BMR in individuals with higher body fat percentages. The revision improved accuracy but Mifflin-St Jeor consistently outperforms it in modern validation studies; it remains in use mainly because of its long history and familiarity in clinical settings. The Katch-McArdle formula takes a fundamentally different approach: BMR = 370 + (21.6 × lean body mass in kg). By excluding fat mass — which is substantially less metabolically active than lean tissue — it corrects the main structural weakness of weight-based equations. When an accurate body-fat percentage is available (from DEXA, hydrostatic weighing, or precise caliper measurement), Katch-McArdle is arguably the most accurate formula for any individual regardless of body composition. The Schofield equations, adopted by the WHO and FAO, are stratified by age group and sex. They were calibrated largely on an Italian military population from the 1980s and have been shown to overestimate BMR for individuals from tropical climates and for very obese individuals — a known limitation that the WHO itself has acknowledged in subsequent technical reports.

For most people using this calculator, Mifflin-St Jeor is the right default. Switch to Katch-McArdle only if you have a reliable body-fat measurement — using an inaccurate body-fat estimate produces a less accurate BMR than Mifflin-St Jeor despite the formula's theoretical superiority. Harris-Benedict is included for reference and for users who want to cross-check against an older established standard. The variation between formulas for the same individual is typically 50–150 kcal/day — meaningful enough to track but smaller than the error introduced by misreporting activity level or food intake.

TDEE, Activity Multipliers, and Why Your Metabolism Adapts to a Deficit

Total Daily Energy Expenditure (TDEE) is the product of BMR and an activity factor. The five-level scale originally described by Harris and Benedict and refined in subsequent research assigns multipliers: Sedentary (desk job, no structured exercise) ×1.2; Lightly active (light exercise 1–3 days per week) ×1.375; Moderately active (exercise 3–5 days per week) ×1.55; Very active (hard exercise 6–7 days per week) ×1.725; Extra active (physical labour job plus hard daily exercise, or twice-daily training) ×1.9. A meaningful practical point is that most office workers who exercise three times per week are at most moderately active — the multipliers are calibrated on full-day activity levels, not just the hour spent in the gym. Selecting the wrong multiplier is the single most common source of systematic error in TDEE calculations, often inflating estimated needs by 200–400 kcal/day.

A large but often overlooked component of TDEE is Non-Exercise Activity Thermogenesis (NEAT) — the energy expended in all physical movement that is not deliberate exercise: walking to the coffee machine, fidgeting, gesturing while talking, maintaining posture, and standing. Research by James Levine at the Mayo Clinic showed that NEAT varies by as much as 2,000 kcal/day between individuals of similar size and occupation. Lean individuals who resist weight gain tend to spontaneously increase NEAT when overfed, while people prone to fat storage do not — a difference that explains much of the observed variation in how easily individuals gain or lose weight under controlled feeding conditions. NEAT is captured imprecisely in the activity multiplier, which is one reason calorie target calculations should always be validated against 2–4 weeks of real-world results.

The most clinically important phenomenon for anyone in a sustained calorie deficit is adaptive thermogenesis: the decrease in TDEE that exceeds what would be predicted from weight loss alone. When caloric intake is restricted, the body reduces NEAT (people move less spontaneously without consciously choosing to), slightly lowers core body temperature, decreases thyroid hormone output, and reduces the energy cost of physical activity by becoming more mechanically efficient. This is the primary mechanism behind the so-called metabolism plateau — the point at which weight loss stalls despite no apparent change in diet. Studies of contestants from the television programme The Biggest Loser found that metabolic adaptation persisted for six years after the competition, with average TDEE running 500–700 kcal/day below what would be predicted from their post-competition body composition. Managing adaptive thermogenesis — through diet breaks, refeeds at or near maintenance calories, and preserving muscle mass via resistance training — is one of the most evidence-supported strategies in long-term weight management.