Health & Fitness

BMR Calculator

Calculate your Basal Metabolic Rate — the calories your body burns at complete rest. Get your TDEE and personalised calorie targets for weight loss, maintenance and muscle gain.

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3 Scientific Formulas
TDEE & Calorie Goals
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🔥
Written & Maintained By
Keeroot Solutions
Digital Product Studio · Coimbatore, India · keeroot.com
This BMR Calculator uses the three most clinically validated metabolic formulas — Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle — cross-referenced with Academy of Nutrition and Dietetics guidelines. Last updated: April 2026. For informational use only — consult a qualified dietitian or physician for personalised nutrition advice.
✅ Clinically validated formulas 🔒 No data stored 📅 Updated April 2026 🆓 Always free
Before You Calculate

What Is BMR — and Why Does It Actually Matter?

April 2026  ·  5 min read  ·  Keeroot Solutions

Basal Metabolic Rate (BMR) is the number of calories your body burns every day just to stay alive — with no food, no movement, no activity of any kind. Breathing, circulating blood, regulating body temperature, repairing cells, maintaining organ function: all of these processes consume energy continuously, even while you sleep. Your BMR is the fuel cost of simply existing.

It is also the most important number in any serious fitness or nutrition plan — and the most commonly misunderstood. Most people who try to lose weight set a calorie target based on a rough guess, an app default, or the vague advice to "eat less." The result is either too aggressive (causing muscle loss, fatigue, and eventual rebound) or too conservative (producing no meaningful change). BMR gives you the scientific baseline from which every calorie target should be calculated.

The Difference Between BMR and TDEE

BMR tells you how many calories your body needs at absolute rest. But you are not at absolute rest — you walk, work, exercise, fidget, and process food. Your Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor that accounts for all of this movement. TDEE is the number you actually use for diet planning.

Think of it this way: BMR is the engine idling in a parked car. TDEE is the fuel your car actually burns on your typical daily drive. Eating at your BMR while being active is the nutritional equivalent of running your engine dry — your body will begin breaking down muscle tissue for fuel, your hormones will shift to conserve energy, and your metabolism will slow in ways that make future weight loss even harder.

A Tale of Two People — Office Worker vs Athlete

Consider two 30-year-old women, both 165 cm tall and weighing 65 kg. Their BMR from the Mifflin-St Jeor formula is identical: approximately 1,465 kcal/day. But their TDEE — the calories they actually need to eat — is completely different:

💼 Office Worker (Sedentary)
BMR: 1,465 kcal
Activity factor: ×1.2
TDEE: ~1,758 kcal/day
Weight loss target: ~1,258–1,458 kcal
🏋️ Athlete (Very Active)
BMR: 1,465 kcal
Activity factor: ×1.725
TDEE: ~2,527 kcal/day
Weight loss target: ~2,027–2,227 kcal

Same BMR. Nearly 770 calories difference in daily needs. If the athlete followed the office worker's calorie target, she would be in a dangerously severe deficit — losing muscle, feeling exhausted, and likely abandoning the plan within weeks. This is why calculating your personal BMR and TDEE, rather than following generic advice, is the foundation of any effective nutrition strategy.

Who Should Use This Calculator

This tool is useful for anyone managing their calorie intake with a specific goal — whether that's losing body fat, gaining muscle, improving athletic performance, or simply understanding their baseline energy needs. It is also valuable for people who have hit a plateau and want to recalculate their needs after significant weight changes (BMR shifts as body weight changes), and for anyone who suspects their current calorie targets are incorrect. The calculator outputs results across three formulas simultaneously so you can compare and choose the most relevant one for your situation. If you know your body fat percentage, the Katch-McArdle formula will give you the most accurate result. Otherwise, use Mifflin-St Jeor — the gold standard for the general population. Also see our BMI Calculator and Calorie Calculator for complementary health insights.

Calculate Your BMR & TDEE

Enter your details to find your Basal Metabolic Rate and total daily calorie needs

yrs
kg
cm
Mifflin-St Jeor
Most accurate ✓
Harris-Benedict
Revised (1984)
Katch-McArdle
Needs body fat %
🔥 Your Basal Metabolic Rate
—
calories / day
—
TDEE: — kcal/day
Daily Calorie Targets by Goal
Formula Comparison
Suggested Macronutrients (at maintenance / TDEE)
Your Health Stats
    Share Your BMR Results

    5 Common BMR Mistakes That Derail Results

    Why most people get their calorie targets wrong — and how to fix it

    Critical Errors
    Stop Making These Nutrition Mistakes

    Most calorie-counting failures trace back to one of five specific errors in how people interpret and apply their BMR and TDEE. Understanding these mistakes is as important as knowing the numbers themselves.

    ❌ Mistake 1: Eating at BMR Level
    The most damaging and most common mistake. BMR is your survival minimum — the calories your body needs at complete rest to keep organs functioning. Eating at BMR while being active creates an extreme deficit. Your body responds by breaking down muscle for fuel, slowing metabolism (metabolic adaptation), and disrupting hunger hormones. The result: you feel exhausted, lose muscle instead of fat, and regain weight rapidly when you stop. Always use TDEE − 300 to 500 kcal for sustainable fat loss.
    ❌ Mistake 2: Overestimating Your Activity Level
    The activity multipliers in the TDEE formula — Sedentary (1.2), Lightly Active (1.375), Moderately Active (1.55) — are frequently misapplied. Most people who "go to the gym 3 times a week" but sit at a desk for 8 hours are Lightly Active at best, not Moderately Active. Overestimating your activity level inflates your TDEE, causing you to eat more than you burn — and wonder why you're not losing weight despite "being in a deficit." When in doubt, choose one level lower than you think is right and adjust based on 2–3 weeks of results.
    ❌ Mistake 3: Not Recalculating After Weight Change
    BMR is calculated from your current body weight. If you lose 5 kg, your BMR drops — meaning the calorie target that produced steady loss when you weighed 85 kg now produces slower or no loss at 80 kg. Most people plateau not because their body has "adapted" mysteriously, but because they never updated their calorie target after losing weight. Recalculate BMR and TDEE every 4–6 weeks or whenever your weight changes by more than 3–4 kg.
    ❌ Mistake 4: Ignoring Thermic Effect of Food (TEF)
    Digesting food costs calories — roughly 10% of total calorie intake for a mixed diet. Protein costs 20–30% of its own calories to digest; carbohydrates 5–10%; fat 0–3%. This means a diet high in processed fat and low in protein requires less energy to digest, effectively increasing net calorie absorption. Switching to a higher-protein diet can create a meaningful additional deficit without eating less — just through the thermic effect difference.
    ❌ Mistake 5: Treating BMR as a Fixed Number
    BMR is not a constant. It changes with age (declines ~2% per decade after 20), with muscle mass changes (resistance training raises it; muscle loss from crash dieting lowers it), with hormonal shifts (thyroid conditions, hormonal contraception, menopause, testosterone levels), and with significant weight changes. Your BMR today is not the same as your BMR from two years ago — and recalculating periodically is essential for keeping your targets accurate.

    Real Example: BMR → TDEE → Weight Loss Plan

    A complete worked example so you can apply the same logic to your own numbers

    Worked Example
    Rahul's Calorie Plan, Step by Step

    Meet Rahul: a 32-year-old male, 178 cm tall, weighing 82 kg, working a desk job (sedentary during the week) but going to the gym 3 times a week. His goal is to lose fat steadily without losing muscle. Here's exactly how to go from raw inputs to a real nutrition plan:

    📊 Step 1: Calculate BMR

    Formula usedMifflin-St Jeor
    Inputs82 kg, 178 cm, Age 32
    Calculation(10×82)+(6.25×178)−(5×32)+5
    = 820+1112.5−160+5= 1,777 kcal
    BMR = 1,777 kcal/day

    ⚡ Step 2: Calculate TDEE

    Activity assessmentLightly Active
    ReasoningDesk job + gym ×3/week
    Activity multiplier× 1.375
    TDEE = 1,777 × 1.375= 2,443 kcal
    TDEE = 2,443 kcal/day

    📉 Step 3: Set Fat Loss Target

    GoalLose ~0.5 kg/week
    Required deficit−500 kcal/day
    Daily calorie target2,443 − 500
    Eat 1,943 kcal/day

    🥩 Step 4: Set Protein Target

    Protein goalPreserve muscle
    Recommended intake1.6–2.2 g per kg
    Rahul's target82 × 2 = 164 g
    Protein calories164 × 4 = 656 kcal
    164g protein/day (33% of intake)
    📋 Rahul's full plan: 1,943 kcal/day · 164g protein · Fill remaining 1,287 kcal with carbohydrates and fat in a ratio that suits his preference. Recalculate in 6 weeks or when weight drops by 3–4 kg, whichever comes first. Track weight daily and use a 7-day average to remove noise.

    Notice that Rahul's fat loss calorie target (1,943 kcal) is still well above his BMR (1,777 kcal). This is intentional. Going below BMR triggers the metabolic and hormonal consequences described above. A sustainable plan preserves muscle, keeps hormones in balance, and produces steady results over months — not crash results that reverse in weeks. Try entering Rahul's numbers — or your own — in the calculator below to see your results.

    BMR Formulas Explained

    The three most widely-used scientific equations for calculating BMR

    The Formulas
    Mifflin, Harris-Benedict & Katch-McArdle
    FormulaEquationBest ForAccuracy
    Mifflin-St Jeor
    (1990)    		 Male: (10×kg) + (6.25×cm) − (5×age) + 5
    Female: (10×kg) + (6.25×cm) − (5×age) − 161    		 General population — most people Most Accurate
    Harris-Benedict
    (Revised 1984)    		 Male: (13.397×kg) + (4.799×cm) − (5.677×age) + 88.362
    Female: (9.247×kg) + (3.098×cm) − (4.330×age) + 447.593    		 Traditional; widely used clinically Good
    Katch-McArdle
    (1975)    		 370 + (21.6 × Lean Body Mass in kg)
    LBM = weight × (1 − body fat %)    		 Athletes who know their body fat % Best with LBM

    The Mifflin-St Jeor formula is the gold standard recommended by the Academy of Nutrition and Dietetics. Validated on modern populations, it is the default choice for most people. The Harris-Benedict formula was originally developed in 1919 and revised by Roza and Shizgal in 1984 — the revised version used here remains accurate for most adults and is still widely used in clinical settings.

    The Katch-McArdle formula is uniquely based on Lean Body Mass (LBM) rather than total body weight. Because muscle tissue burns far more calories than fat, this formula is more precise for athletic or muscular individuals — but it requires knowing your body fat percentage.

    ⚖️ Which should you use? Start with Mifflin-St Jeor. If you're an athlete or have measured your body fat percentage, switch to Katch-McArdle for a more accurate personalised result. The calculator shows all three side-by-side so you can see how they compare for your inputs.

    Activity Level Guide

    How your daily activity multiplies your BMR to give your true TDEE

    Activity Multiplier
    Matching Your Lifestyle to the Right Factor

    TDEE = BMR × Activity Factor. Choosing the correct activity level is critical — most people overestimate their activity, which leads to eating more than they burn.

    🛋️
    Sedentary

    Desk job, minimal walking, no structured exercise

    × 1.2
    🚶
    Lightly Active

    Light exercise or sport 1–3 days per week

    × 1.375
    🏃
    Moderately Active

    Moderate exercise or sport 3–5 days per week

    × 1.55
    🏋️
    Very Active

    Hard exercise or sport 6–7 days per week

    × 1.725
    ⚡
    Extremely Active

    Very hard exercise, physical job, or twice-daily training

    × 1.9
    💡
    Be Honest

    Most office workers should use 1.2–1.375. Overestimating activity is the #1 reason diets fail

    Choose wisely

    How BMR Is Calculated

    Step-by-step from raw inputs to your personalised calorie target

    Step by Step
    From Biometrics to Calorie Goal
    • 1
      Enter Your Biometrics

      Age, biological sex, weight and height are required by all three formulas. These four inputs determine your body's base energy requirement before any activity is considered.

    • 2
      Calculate Raw BMR

      The formula processes your inputs to produce a BMR in kcal/day — the calories your body burns at absolute rest, keeping organs, brain and circulation running 24/7.

    • 3
      Apply the Activity Multiplier

      TDEE = BMR × Activity Factor. This accounts for all energy expended during the day: walking, working, exercising, and even fidgeting (Non-Exercise Activity Thermogenesis — NEAT).

    • 4
      Set Your Calorie Goal

      Weight loss: TDEE − 300–500 kcal. Maintenance: TDEE. Muscle gain: TDEE + 200–300 kcal. The calculator displays targets for all major goals: aggressive loss, moderate loss, maintenance, lean bulk and aggressive bulk.

    • 5
      Distribute Your Macros

      Protein (4 kcal/g), Carbohydrates (4 kcal/g) and Fat (9 kcal/g). A starting split of ~30% protein / 40% carbs / 30% fat suits most goals. High-protein approaches (35–40%) better preserve muscle during a deficit.

    Quick formula reference (Mifflin-St Jeor):
    BMR (Male) = (10 × kg) + (6.25 × cm) − (5 × age) + 5
    BMR (Female) = (10 × kg) + (6.25 × cm) − (5 × age) − 161
    TDEE = BMR × Activity Factor
    Fat loss ≈ TDEE − 500 kcal/day → ~0.5 kg/week

    Interesting Facts About Metabolism & Calories

    Surprising science about how your body burns energy every day

    Did You Know?
    Fascinating Metabolism Facts
    🧠
    Your Brain Burns 20% of Calories

    Despite being only 2% of body weight, the human brain consumes roughly 20% of your total resting energy — around 300–400 kcal/day. Intense thinking barely raises this; the brain maintains a fairly constant burn rate.

    ❄️
    Cold Exposure Boosts Metabolism

    Cold temperatures activate brown adipose tissue, which burns calories to generate heat. Even drinking cold water causes a mild thermogenic effect as your body warms it to core temperature.

    💪
    Muscle Burns 3× More Than Fat

    Each kilogram of muscle burns approximately 13 kcal/day at rest, versus ~4.5 kcal/day for fat tissue. This is why resistance training raises your BMR even on rest days — the muscles are always burning.

    😴
    You Burn Calories While Sleeping

    Your BMR operates continuously — including during sleep. The body performs critical repair, memory consolidation and restoration while you rest, burning roughly 50–80 kcal per hour depending on your BMR.

    🍗
    Protein Has the Highest TEF

    The Thermic Effect of Food (TEF) is the energy cost of digesting food. Protein costs 20–30% of its own calories to digest — compared to 5–10% for carbs and just 0–3% for fat. This is why high-protein diets have an edge.

    📉
    Crash Diets Slow Your Metabolism

    Eating far below BMR triggers metabolic adaptation — the body can lower BMR by up to 15–20% to conserve energy. This is why extreme calorie restriction stalls weight loss over time and dramatically increases the chance of weight regain.

    ☕
    Caffeine Raises BMR by 3–11%

    Caffeine is one of the few substances with a clinically proven thermogenic effect, temporarily raising BMR by 3–11% and enhancing fat oxidation. The effect diminishes with regular use as the body builds tolerance.

    🏔️
    Altitude Increases Calorie Burn

    At high altitudes, the body works harder to oxygenate blood and maintain temperature, raising calorie burn by 10–28%. Elite mountaineers can burn 4,000–6,000+ kcal per day at extreme elevations.

    Frequently Asked Questions

    Common questions about BMR, TDEE and calorie targets

    What is the difference between BMR and TDEE?
    BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — just to keep organs functioning. TDEE (Total Daily Energy Expenditure) is BMR multiplied by your activity factor, representing your actual daily calorie burn including all movement. Always use TDEE — not BMR — for diet planning. Eating at BMR while active would place most people in a dangerously severe calorie deficit.
    How accurate are these BMR formulas?
    BMR formulas estimate metabolic rate with a margin of error of roughly ±10–15%. The Mifflin-St Jeor formula is the most accurate for the general population. Use the result as a starting point, then track your weight for 2–4 weeks at that intake. If your weight isn't changing as expected, adjust by 100–200 kcal up or down.
    Should I eat at my BMR to lose weight?
    No. Eating at BMR is only appropriate if you are completely bed-bound. For active people, eating at BMR creates an extreme deficit causing muscle loss, hormonal disruption and metabolic adaptation. Instead, aim for 300–500 kcal below your TDEE — this produces steady, sustainable fat loss of ~0.3–0.5 kg per week while preserving lean muscle mass.
    Why does the calculator ask for biological sex?
    The BMR formulas use different equations for male and female biology because, on average, males have more muscle mass and less fat at equivalent body weights — resulting in a higher metabolic rate. The calculator uses biological sex as a proxy for body composition. If you have your body fat percentage, switch to the Katch-McArdle formula which bypasses the sex variable entirely and uses Lean Body Mass directly.
    Can I increase my BMR?
    Yes. The most effective long-term strategy is building muscle mass through resistance training — muscle tissue burns significantly more calories at rest than fat. Other supporting factors: adequate sleep (poor sleep disrupts hunger hormones and lowers BMR), avoiding chronic crash diets (which cause metabolic adaptation), staying well-hydrated, and maintaining adequate protein intake to preserve muscle during a calorie deficit.
    Is this tool private?
    Yes, completely. All calculations happen entirely in your browser using JavaScript. No data you enter — age, weight, height or body fat — is ever sent to a server, stored, or logged anywhere. Your information disappears when you close or refresh the tab.