BMR Calculator

Calculate BMR: Basal Metabolic Rate & Daily Calorie Needs

Your Basal Metabolic Rate is the number of calories your body burns at complete rest to sustain life. Breathing, circulating blood, regulating temperature, and repairing cells all require energy, and BMR accounts for roughly 60 to 75 percent of your total daily calorie burn. That is a huge chunk. Knowing your BMR gives you a factual starting point instead of guessing whether you are eating too much or too little.

BMR versus TDEE: Understanding the Difference

BMR is only part of the picture. Your Total Daily Energy Expenditure (TDEE) adds three more components: the thermic effect of food (energy used to digest and process what you eat), non-exercise activity thermogenesis (walking to the car, fidgeting, standing), and planned exercise. To estimate TDEE, multiply your BMR by an activity factor. Sedentary people use 1.2, lightly active 1.375, moderately active 1.55, active 1.725, and very active 1.9. If your BMR is 1,500 calories and you exercise three times a week, your TDEE would be around 2,325 calories. That is the number to use when planning weight changes.

Mifflin-St Jeor versus Harris-Benedict

Two equations dominate BMR estimation. The Harris-Benedict equation dates to 1919 and was revised in 1984. It works reasonably well for many people but tends to overestimate calories in overweight individuals. The Mifflin-St Jeor equation, developed in 1990, is now considered more accurate for the general population. For a 35-year-old woman who is 165 cm tall and weighs 70 kg, Mifflin-St Jeor gives a BMR of about 1,435 calories, while the older Harris-Benedict formula gives roughly 1,490 calories. The difference is small for some and larger for others. Our calculator uses Mifflin-St Jeor because study after study confirms it predicts resting energy expenditure more reliably across a wide range of body types.

Why BMR Matters for Weight Management

Weight management comes down to the gap between calories in and calories out. BMR is the largest component of calories out, so underestimating or overestimating it throws off your entire plan. If you set your calorie target below your BMR, you risk metabolic slowdown, muscle loss, and nutrient deficiencies. If you ignore it entirely and follow generic advice like eat 1,200 calories, you might be starving yourself unnecessarily or eating too much to lose weight. BMR gives you a personalised floor to work from, not a random internet number.

Factors That Raise or Lower Your BMR

Muscle tissue burns about three times as many calories as fat tissue at rest, so strength training is one of the few ways to meaningfully increase BMR. Thyroid hormones regulate metabolic rate, which is why untreated hypothyroidism can drop BMR by 15 percent or more. Age is another factor. After 30, BMR declines roughly 2 to 3 percent per decade, largely due to gradual muscle loss. This is not inevitable. People who maintain muscle through resistance training see a much smaller decline. Fever, pregnancy, and certain medications also temporarily raise BMR, while calorie restriction lowers it as the body adapts to perceived scarcity.

How to Use Your BMR Number

Start by calculating your BMR, then multiply by the appropriate activity factor to get TDEE. From there, subtract 300 to 500 calories for fat loss or add 250 to 500 for muscle gain. Track your weight for three to four weeks and adjust. If you are losing faster than expected, add a small snack. If you are not losing, reduce slightly. Your actual metabolism may differ from the formula by up to 10 percent, so real-world data is the ultimate truth.

Questions You Might Have About BMR