BMR Calculator

What your BMR means

Your Basal Metabolic Rate is the energy your body needs to keep its core systems running while at complete rest — the heart beating, the lungs breathing, cells repairing, and body temperature steady. It is the largest single component of the calories you burn each day, typically accounting for 60–70% of your total expenditure.

Think of BMR as the minimum fuel your body needs just to stay alive. Even if you spent an entire day lying still in bed, your body would still burn this many calories. That is why BMR is sometimes called your "resting metabolism" — it is the baseline from which all other calorie burn is measured.

BMR vs RMR — resting metabolic rate

Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) are closely related but measured under slightly different conditions. BMR is measured after a full night of sleep and 12 hours of fasting, in a thermoneutral environment, with the subject completely at rest. RMR is measured under less strict conditions — no fasting requirement, and the subject may have been lightly active earlier in the day.

Because of these looser conditions, RMR is typically 5–10% higher than BMR. In everyday language, the two terms are used interchangeably. Our BMR calculator estimates RMR using the Mifflin-St Jeor equation, which is the most widely accepted predictive formula.

BMR vs TDEE

BMR is only part of the picture. Your Total Daily Energy Expenditure (TDEE) is the total number of calories you burn in a day, and it includes four components:

• BMR (60–70%): calories burned at rest for basic life functions
• Thermic Effect of Food (10%): calories burned digesting and processing nutrients
• Non-Exercise Activity Thermogenesis (15–30%): calories burned from daily movement — walking, fidgeting, standing
• Exercise Activity Thermogenesis (10–20%): calories burned from structured exercise

To find your full daily needs, multiply your BMR by an activity factor. Use the TDEE calculator for a detailed breakdown, or the maintenance calories calculator for a simpler tool.

What affects your BMR

Several factors influence how many calories your body burns at rest:

• Muscle mass: Muscle tissue is metabolically active and burns more calories at rest than fat tissue. This is the single most impactful lever you can control through resistance training.
• Body size: Larger bodies — taller and heavier — require more energy to maintain basic functions simply because there is more tissue to support.
• Age: BMR declines gradually with age, roughly 2–3% per decade after 30, driven largely by the loss of muscle mass and changes in organ metabolism.
• Sex: Men typically have higher BMRs than women of the same age and size, largely due to greater muscle mass and lower body fat percentage.
• Genetics and hormones: Thyroid function, genetic predisposition, and hormonal balance cause individual variation. Some people naturally burn more or fewer calories at rest.
• Diet and fasting: Severe calorie restriction can temporarily lower BMR as the body adapts to conserve energy — a phenomenon sometimes called "adaptive thermogenesis."

How to increase your BMR

While some factors like age and genetics are fixed, there are proven ways to raise your BMR over time:

1. Build muscle: Resistance training is the most effective strategy. Each kilogram of muscle adds roughly 13–15 calories per day at rest.
2. Eat enough protein: Protein has a higher thermic effect than carbs or fat, meaning your body burns more calories digesting it. It also supports muscle maintenance and growth.
3. Stay active throughout the day: Walking, standing, and general movement increase your non-exercise calorie burn, which supports a higher overall metabolic rate.
4. Get quality sleep: Poor sleep disrupts hormones that regulate metabolism, including cortisol and growth hormone.
5. Avoid extreme dieting: Very low-calorie diets can cause your body to lower its BMR as a survival mechanism. A moderate deficit preserves metabolic rate.

Common BMR myths

Myth: "Skinny people have higher BMRs." Not necessarily. Larger bodies, even with higher body fat, often have higher BMRs because there is more total tissue to maintain. Muscle mass matters more than body weight alone.

Myth: "You can dramatically boost your BMR with supplements." Most metabolism-boosting supplements have minimal real-world impact. Caffeine may raise BMR slightly and temporarily, but the effect is small and diminishes with tolerance.

Myth: "Eating more meals speeds up your metabolism." The thermic effect of food depends on total calorie and protein intake, not meal frequency. Eating three meals or six meals produces the same total thermic effect for the same calories.

Myth: "Your BMR is fixed and unchangeable." While your BMR has a genetic baseline, it is not fixed. Building muscle, changing body composition, and adjusting hormonal health can all shift your BMR over time.

Real BMR calculation examples — Mifflin-St Jeor

The Mifflin-St Jeor equation is the current standard for estimating BMR. Here are worked examples:

Profile	Formula	BMR Result
30-year-old man, 80 kg, 180 cm	10 × 80 + 6.25 × 180 − 5 × 30 + 5	~1,825 kcal/day
30-year-old woman, 65 kg, 165 cm	10 × 65 + 6.25 × 165 − 5 × 30 − 161	~1,377 kcal/day
50-year-old man, 90 kg, 178 cm	10 × 90 + 6.25 × 178 − 5 × 50 + 5	~1,870 kcal/day
50-year-old woman, 75 kg, 163 cm	10 × 75 + 6.25 × 163 − 5 × 50 − 161	~1,424 kcal/day

These are estimates. For your personal BMR, enter your exact stats into the BMR calculator above.

Using BMR for weight loss and weight gain

Your BMR is the foundation for any weight goal. Here is how to use it:

For weight loss: Calculate your BMR, then estimate your TDEE by applying your activity factor. Subtract 250–500 calories from TDEE for a moderate, sustainable deficit. Never drop below 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision. The weight loss calculator can automate this process.

For weight gain: Add 250–500 calories to your TDEE for a lean bulk. Prioritize protein intake and combine with resistance training to ensure the extra calories build muscle rather than fat. The weight gain calculator helps with this.

For maintenance: Eat at your TDEE. Recalculate every 4–6 weeks as your body composition changes. Use the maintenance calories calculator for a quick estimate.

Related tools and guides

• TDEE Calculator — find your total daily energy expenditure
• Macro Calculator — split your calories into protein, carbs, and fats
• Lean Body Mass Calculator — estimate your fat-free mass
• Body Fat Calculator — estimate your body fat percentage
• Weight Loss Calculator — get a timeline and calorie targets
• Protein Calculator — find your daily protein target
• Maintenance Calories Guide — how to find and use your maintenance level
• Calorie Deficit Guide — how to create a sustainable deficit
• Calorie Surplus Guide — how to gain weight leanly
• BMR Equations Guide — compare Mifflin-St Jeor vs Harris-Benedict

Sources and further reading

These independent, authoritative sources inform the methods used on this page.

• A new predictive equation for resting energy expenditure — Mifflin & St Jeor (1990)
• Basal metabolic rate — Wikipedia summary of methods