🔥 BMR / TDEE

About this calculator

Your basal metabolic rate (BMR) is the energy your body burns at rest to keep you alive — breathing, circulation, cell repair. This calculator uses the Mifflin-St Jeor equation (weight, height, age, sex) to estimate BMR, then multiplies it by an activity factor (sedentary to very active) to get your total daily energy expenditure (TDEE) — the calories you burn on a typical day. Enter your details, pick the activity level that honestly matches your week, and get both numbers.

Tip: eat roughly at TDEE to maintain weight, or 300–500 calories below to lose about a pound a week — smaller, sustainable deficits beat crash diets every time.

How to read your BMR and TDEE

Your BMR is the energy your body spends in 24 hours doing nothing but staying alive: breathing, circulating blood, holding body temperature and running your organs. Your brain and liver alone account for a large share of it. Nobody actually lives at BMR, so the calculator multiplies it by an activity factor to estimate your total daily energy expenditure, or TDEE, which is the number that matters for eating decisions. The Mifflin-St Jeor formula behind this calculator is the most accurate of the common equations, but it is still an estimate. For most people it lands within about 10 percent of the measured value, which on a 2,500 calorie day is a 250 calorie band of uncertainty. It also cannot see your body composition: muscle tissue burns more than fat tissue at rest, so two people with identical age, height, weight and sex can have genuinely different burn rates. Use the result as a well informed starting point, then let two to three weeks of real weight trend refine it. It is also why two calculators using slightly different formulas can disagree by a hundred calories or more and both still be reasonable.

A worked example

Consider a man of 42, 178 cm tall, weighing 86 kg. His BMR is 10 times 86, plus 6.25 times 178, minus 5 times 42, plus 5, which works out to 1,768 calories a day. He works at a desk but trains at the gym three times a week, which counts as moderately active, a factor of 1.55. His TDEE is therefore about 2,740 calories a day. The activity factor does heavy lifting here, as this list shows for the same man:

• Sedentary, factor 1.2: about 2,120 calories
• Lightly active, factor 1.375: about 2,430 calories
• Moderately active, factor 1.55: about 2,740 calories
• Very active, factor 1.725: about 3,050 calories

Notice that one step up or down the activity ladder moves his target by roughly 300 calories, as much as a small meal. Choosing the honest activity level matters more than any other input.

Common mistakes

• Eating at your BMR. BMR excludes every step you take and every meal you digest, so eating at BMR usually means a far larger deficit than intended.
• Flattering your activity level. A job on your feet feels active, but the moderate and high factors assume sustained exercise most days. When in doubt, pick the lower factor and let your weight trend correct you.
• Never recalculating. Losing 10 kg lowers BMR by about 100 calories from the weight term alone, before any other adaptation, so an old target quietly becomes wrong.
• Chasing precision the formula cannot give. A result of 1,768 does not mean 1,770 causes gain and 1,760 causes loss; work with the range, not the digit.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is the energy your body burns at complete rest over 24 hours, just staying alive. TDEE is BMR multiplied by an activity factor, so it includes work, walking, exercise and digestion. TDEE estimates your real maintenance calories, which is the figure eating decisions should be based on.

How accurate is the Mifflin-St Jeor formula?

For most adults it lands within about 10 percent of the value measured in a lab, which makes it the most reliable of the quick formulas. Individual results vary with body composition and health, so treat your figure as a starting estimate and correct it using two to three weeks of weight trend.

Does having more muscle raise my BMR?

Yes. Muscle and organ tissue burn far more energy at rest than fat tissue does, so a muscular person burns more than a softer person of identical weight, height and age. Standard formulas cannot see that difference; equations that use lean body mass, such as Katch-McArdle, account for it.

Why did my BMR drop after I lost weight?

A smaller body costs less to maintain and move, so some drop is simple arithmetic: each kilogram lost removes about 10 calories from the weight term alone. There can also be a modest adaptive slowdown beyond that. Recalculate your targets every 5 to 7 kg lost to keep them honest.