Calculate your resting metabolic rate using Mifflin-St Jeor, Harris-Benedict, Katch-McArdle, and Cunningham formulas. Get TDEE, calorie targets, and macronutrient estimates.
Your resting metabolic rate (RMR) — the number of calories your body burns at complete rest to maintain basic life functions like breathing, circulation, and cell repair — accounts for a large share of total daily energy expenditure. Understanding RMR helps frame broader calorie estimates for maintenance, fat loss, or weight gain.
This calculator computes RMR using four established formulas: Mifflin-St Jeor, the revised Harris-Benedict equation, Katch-McArdle, and Cunningham. Comparing several formulas gives you a range instead of forcing one estimate to do all the work, which is useful when body composition or training status may shift the result.
Beyond RMR, the page applies standard activity multipliers to estimate Total Daily Energy Expenditure (TDEE) and shows example calorie and macro ranges. Those outputs are starting estimates for planning, not fixed prescriptions.
Whether you are trying to lose weight, gain weight, or maintain your current intake, knowing your RMR and TDEE gives you a better starting estimate than guessing. This calculator compares several formulas so you can work from a range and then adjust according to weight trend, training response, and hunger.
Mifflin-St Jeor: Males = 10×weight(kg) + 6.25×height(cm) − 5×age + 5; Females = 10×weight + 6.25×height − 5×age − 161 Harris-Benedict (1984): Males = 88.362 + 13.397×weight + 4.799×height − 5.677×age; Females = 447.593 + 9.247×weight + 3.098×height − 4.330×age Katch-McArdle: 370 + 21.6 × Lean Body Mass (kg) Cunningham: 500 + 22 × Lean Body Mass (kg) TDEE = RMR × Activity Multiplier
Result: Mifflin-St Jeor: 1,780 kcal, Harris-Benedict: 1,853 kcal, TDEE: 2,817 kcal
Mifflin-St Jeor: 10×80 + 6.25×178 − 5×35 + 5 = 800 + 1112.5 − 175 + 5 = 1742.5 ≈ 1,780 kcal. Average RMR ≈ 1,817 kcal × 1.55 (moderate activity) = TDEE of ~2,817 kcal. That TDEE can then be used as a starting point for maintenance or for a modest deficit or surplus.
RMR estimates are useful for setting a starting calorie range before you decide whether to maintain intake, create a deficit, or add a surplus. They work best when paired with a few weeks of real-world tracking rather than treated as exact measurements.
Each equation was built from a different population and set of assumptions. Weight-based formulas work reasonably well for many adults, while lean-mass-based formulas can be more informative when body fat percentage is known. Seeing the formulas side by side can be more useful than assuming any one output is universally correct.
Use consistent units, check that your activity level is realistic, and treat the final number as a starting estimate. If your weight, appetite, and training response do not match the output over time, adjust intake rather than assuming the formula must be exact.
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This calculator estimates resting metabolic rate with several published equations, then applies standard activity multipliers to create a Total Daily Energy Expenditure worksheet. If body fat percentage is provided, the page also uses lean-mass-based equations so the range can be compared with the weight-based formulas.
These outputs are planning estimates. They are useful for setting a starting calorie range, but they are not the same as indirect calorimetry and should be adjusted against real-world weight trend, training response, and appetite.
BMR (Basal Metabolic Rate) is measured under strict conditions (12-hour fast, 8 hours sleep, thermoneutral environment). RMR (Resting Metabolic Rate) is measured under less strict resting conditions and is typically 10–20% higher than BMR. For practical purposes, the terms are often used interchangeably.
There is no single formula that fits everyone equally well. Mifflin-St Jeor is commonly used as a general starting point, while Katch-McArdle can be more useful when lean body mass is known. Harris-Benedict is still widely cited but may run a bit higher for some people.
Muscle tissue is metabolically active (burns ~6 kcal/kg/day), while fat tissue is relatively inert (~2 kcal/kg/day). Two people weighing 80 kg may have very different RMR if one has 15% body fat (68 kg lean mass) and another has 30% (56 kg lean mass). Katch-McArdle uses lean mass directly for this reason.
Most have minimal or no effect. Caffeine temporarily increases metabolic rate by 3–11%, and capsaicin has small effects. No supplement replaces the metabolic impact of increasing lean body mass through resistance training, which permanently raises RMR.
Yes, RMR decreases approximately 1–2% per decade after age 20, primarily due to loss of lean body mass (sarcopenia). However, resistance training can significantly attenuate this decline by maintaining muscle mass.
Activity multipliers add significant uncertainty. Most online TDEE estimates are within ±15% of actual expenditure. For better accuracy, track food intake and weight changes over 2–3 weeks, then adjust based on actual results.