BMR Calculator
Calculate your Basal Metabolic Rate and Total Daily Energy Expenditure
Mifflin-St Jeor is considered the most accurate for most people.
Results & Details
// TDEE by Activity Level
// Daily Calories by Goal
// Formula Comparison
What Is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions — breathing, circulation, cell production — while at complete rest. It represents your minimum caloric requirement just to stay alive.
What Is TDEE?
Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor. It represents the total calories you burn in a day accounting for physical activity. TDEE is the most useful figure for setting calorie targets for weight loss, maintenance, or gain.
BMR Formulas
Which Formula Is Most Accurate?
The Mifflin-St Jeor equation is generally considered the most accurate for the general population and is recommended by the Academy of Nutrition and Dietetics. The Katch-McArdle formula can be more precise for lean athletes who know their body fat percentage, as it accounts for lean mass directly.
Using TDEE for Weight Goals
A deficit of 500 calories per day below TDEE produces approximately 0.5 kg (1 lb) of fat loss per week. A surplus of 500 calories produces approximately 0.5 kg of gain per week. These are estimates — individual responses vary based on metabolism, adherence, and other factors.
BMR: Your Body's Idle Speed, Properly Explained
Built and verified by Andrius R. · Updated June 2026
Basal Metabolic Rate is the energy your body burns at complete rest — keeping your heart beating, lungs breathing, brain running, cells repairing. It's typically the largest share of your daily calorie burn (60–70% for most people), which makes estimating it well worth doing carefully.
The three formulas, head to head
| Equation | BMR estimate | Notes |
|---|---|---|
| Mifflin-St Jeor (1990) | ~1,414 kcal | Most accurate for general adult populations; the default here |
| Harris-Benedict (revised) | ~1,464 kcal | The 1919 classic, revised 1984; tends to overestimate slightly |
| Katch-McArdle (at 25% body fat) | ~1,504 kcal | Uses lean mass instead of weight; best for lean/muscular people — needs a body-fat estimate |
A ~90 kcal spread between formulas for the same person — a useful reminder that every BMR figure is an estimate with roughly ±10% uncertainty, not a measurement.
BMR vs RMR vs TDEE — three terms people mix up
BMR is measured under strict lab conditions (fasted, rested, lying still, thermally neutral). RMR (resting metabolic rate) is the slightly looser everyday version, typically a few percent higher. TDEE (total daily energy expenditure) is BMR scaled up by your activity — the number that actually matters for eating decisions. The chain: BMR → multiply by an activity factor (1.2 sedentary to ~1.9 very active) → TDEE → adjust for your goal. Our calorie calculator handles the full chain.
What actually moves your BMR
- Lean mass — the big one. Muscle is metabolically active tissue; this is most of why men average higher BMRs than women and why resistance training defends your metabolism.
- Age: BMR drifts down a few percent per decade in adulthood — driven largely by muscle loss, which is partly preventable. (Notably, recent large-scale research found metabolism is more stable from ~20 to ~60 than previously believed, when adjusted for body composition.)
- Body size: more body = more cells to run. Heavier people have higher BMRs, which is why maintenance calories fall as weight is lost.
- Genetics, hormones, temperature: real but smaller effects. Thyroid disorders are the major medical exception — if your measured reality diverges wildly from every formula, that's a doctor conversation.
The "starvation mode" myth, corrected
Severe under-eating does slow metabolism — but modestly. The documented effect (adaptive thermogenesis) is on the order of 10–15% beyond what's expected from weight loss itself, not the metabolic shutdown internet folklore describes; you cannot gain weight in a true calorie deficit. The genuine reasons crash diets fail are muscle loss dragging BMR down, hunger hormones rebounding, and unsustainable restriction collapsing into rebound eating. A moderate deficit with adequate protein and resistance training sidesteps all three — slower, but it actually sticks.
Why two people the same size burn different amounts
Even with identical stats, real metabolisms vary — body composition, fidgeting and daily movement (NEAT can differ by hundreds of kcal/day between individuals), hormones, and measurement error all stack. So treat your calculated BMR as a well-informed starting point: hold a calorie target for 2–3 weeks, watch the weekly trend on the scale, and adjust. Your own data always outranks the formula.
// TDEE Not BMR
Use TDEE — not BMR — to set your daily calorie targets. BMR is the floor; TDEE accounts for what you actually burn.
// Deficit Limit
Don't eat below BMR for extended periods. Very low calorie diets can cause muscle loss, nutrient deficiencies, and metabolic adaptation.
// Re-calculate Often
BMR changes as you lose weight. Recalculate every 5–10 kg of weight change to keep your targets accurate.
// Muscle Raises BMR
Muscle tissue burns more calories at rest than fat. Resistance training raises BMR over time, making weight management easier.