BMR Calculator

The BMR Calculator estimates Basal Metabolic Rate (BMR) and converts it into an activity-adjusted Total Daily Energy Expenditure (TDEE). Personal data, a choice of formula, and an activity level combine into daily calorie targets for maintenance, weight loss, or weight gain, shown in Calories or Kilojoules and adjustable by a flat surplus or deficit goal.

Accurate, consistent results depend on a few inputs:

• Height and weight, in Imperial or Metric units, convert automatically when units are switched.
• Age and sex both factor into the formula; age must fall within the supported range for a valid result.
• Three BMR formulas are available: Mifflin-St Jeor, Revised Harris-Benedict, or Katch-McArdle. Katch-McArdle additionally requires body fat percent to compute lean body mass.
• Activity level ranges from Sedentary through Extreme, matched to the routine notes shown in the results table.
• A goal of Maintain, Lose, or Gain applies a standard adjustment to TDEE.
• Results display in Calories or Kilojoules.

The core formulas, as plain-text equations:

• Mifflin-St Jeor (male): BMR = 10 · W + 6.25 · H − 5 · A + 5
• Mifflin-St Jeor (female): BMR = 10 · W + 6.25 · H − 5 · A − 161
• Revised Harris-Benedict (male): BMR = 13.397 · W + 4.799 · H − 5.677 · A + 88.362
• Revised Harris-Benedict (female): BMR = 9.247 · W + 3.098 · H − 4.330 · A + 447.593
• Katch-McArdle: LBM = W × (1 − BF%); BMR = 370 + 21.6 · LBM
• Activity factor (TDEE): Sedentary 1.20; Somewhat Active 1.375; Active 1.463; Very Active 1.55; Intense 1.725; Extreme 1.90
• TDEE = BMR × activity factor
• Goal calories: Maintain = TDEE; Lose = TDEE − 500; Gain = TDEE + 500
• Kilojoules conversion: kJ = Calories × 4.184
• Unit conversions: 1 in = 2.54 cm; 1 ft = 30.48 cm; 1 lb = 0.453592 kg

Matching the activity selection to its routine notes keeps the estimate meaningful, and recalculating after a meaningful change in weight, body fat percent, training volume, or routine keeps the target current.

Basal Metabolic Rate underlies calorie targets across a range of health and fitness goals. The formulas guide nutrition planning, training adjustments, and progress tracking, supporting energy balance with greater consistency.

• Weight maintenance matches daily calorie intake to the activity-adjusted total energy expenditure (TDEE).
• Weight reduction comes from a sustainable caloric deficit of 500 to 750 calories below TDEE, losing about 1 to 1.5 pounds per week.
• Muscle mass gain comes from adding 300 to 500 calories above TDEE to support strength training and recovery.
• Comparing formulas side by side, Mifflin-St Jeor against Revised Harris-Benedict and Katch-McArdle, shows how each estimates BMR differently.
• Activity-level assessment checks calorie ranges across Sedentary, Somewhat Active, Active, Very Active, Intense, and Extreme routines, aligned with the matching notes.
• Medical consultations benefit from sharing calculated values with healthcare providers for dietary or metabolic assessments.
• Training program design uses BMR and TDEE to set calorie intake for cutting, bulking, or maintenance phases.
• Progress tracking recalculates BMR as age, weight, or body composition change, keeping calorie targets accurate.
• Energy balance depends on BMR, activity factors, and dietary choices together.
• Recovery days call for adjusted intake when physical activity is lower, to maintain energy balance over time.
• Plateaus respond to modified calorie intake and activity multipliers when weight loss or gain stalls.

Activity levels correspond to standard multipliers: Sedentary (little or no exercise), Somewhat Active (light exercise 1 to 3 days per week), Active (moderate exercise 3 to 5 days per week), Very Active (hard exercise 6 to 7 days per week), Intense (very hard training or physical job), and Extreme (daily intense exercise or multiple training sessions). Matching lifestyle to the correct category keeps the calorie target accurate.

This tool is intended for informational and educational purposes only. It does not provide medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for any health-related concerns or decisions.