BMR Calculator
Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE).
The Formula
BMR = 10W + 6.25H − 5A + 5
Mifflin-St Jeor (women):
BMR = 10W + 6.25H − 5A − 161
W = kg · H = cm · A = age
= (10 × 80) + (6.25 × 180) − (5 × 30) + 5
= 800 + 1,125 − 150 + 5
BMR = 1,780 calories/day
What Is BMR?
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to keep you alive — breathing, circulating blood, regulating temperature, and maintaining organ function. Think of it as the energy cost of simply existing. BMR accounts for roughly 60–75% of your total daily calorie burn, which means even on a rest day with zero exercise, your body is still burning the majority of your daily calories. It is the foundation of any nutrition or weight loss plan.
What Is TDEE and Why Does It Matter?
Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor to account for everything you do throughout the day — exercise, walking, fidgeting, working. Eating at your TDEE maintains your current weight. Eating below it creates a deficit and causes fat loss. Eating above it creates a surplus, which supports muscle gain (or fat gain, depending on the surplus size and what you eat). TDEE is the number most people need when setting calorie targets.
The Mifflin-St Jeor Equation
This calculator uses the Mifflin-St Jeor equation, published in 1990 and widely regarded as the most accurate formula for estimating BMR in the general population. For men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) + 5. For women: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161. The older Harris-Benedict equation is still sometimes used but tends to overestimate BMR slightly compared to Mifflin-St Jeor.
Frequently Asked Questions
How is TDEE calculated from BMR?
TDEE is BMR multiplied by an activity multiplier: 1.2 for sedentary (desk job, little exercise), 1.375 for lightly active (light exercise 1–3 days per week), 1.55 for moderately active (exercise 3–5 days per week), 1.725 for very active (hard exercise 6–7 days per week), and 1.9 for extra active (physical job plus daily training). Most people overestimate their activity level — when in doubt, go one category lower.
Can I increase my BMR?
Yes. The most effective method is building muscle mass through strength training. Muscle tissue is metabolically active — it burns more calories at rest than fat tissue. Adding 5–10 pounds of lean muscle can raise BMR by 50–100 calories per day. Adequate protein intake (0.7–1g per pound of body weight) is essential to support muscle retention and growth, especially in a calorie deficit.
Does BMR decrease with age?
Yes, gradually. BMR typically decreases about 1–2% per decade after age 20, primarily due to muscle loss (sarcopenia). The good news: much of this decline is preventable with regular strength training and adequate protein intake. This is one of the most compelling reasons to lift weights as you age — it preserves the metabolically active tissue that keeps your metabolism from slowing.
Why do men have higher BMRs than women?
Men generally have higher BMRs because they carry more lean muscle mass and less body fat than women of similar weight, and muscle burns more calories at rest than fat. Hormonal differences also play a role. This is reflected directly in the Mifflin-St Jeor formula, which adds 5 calories for men and subtracts 161 for women at the end of the calculation.
How accurate is a BMR calculator?
BMR formulas are population averages and individual results can vary by 10–15%. Factors like thyroid function, medications, genetics, and recent diet history all affect actual metabolic rate. For most people, calculated BMR is accurate enough for practical nutrition planning. If you are consistently not seeing expected results from your calorie targets, adjusting based on actual real-world results is more reliable than chasing a more precise formula.