BMR Calculator

Calculate your Basal Metabolic Rate (BMR) and estimated daily calorie needs at different activity levels using the Mifflin-St Jeor equation. Free, instant, no signup.

Formula: BMR (male) = 10×kg + 6.25×cm − 5×age + 5 | (female) = 10×kg + 6.25×cm − 5×age − 161

How to use the BMR Calculator

  1. Enter your values. Fill in the fields with your numbers.
  2. Calculate. Press Calculate to run the bmr calculator.
  3. Use the result. Copy the result or try a related tool next.

Why use our BMR Calculator

Instant results. Enter your figures and the bmr calculator returns an answer in seconds.
Free & private. Runs in your browser — no signup, and nothing is sent to a server.
Accurate. Uses standard formulas so you can rely on the numbers.

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About the BMR Calculator

The BMR Calculator estimates your Basal Metabolic Rate, the number of calories your body burns in a 24-hour period doing nothing but staying alive: breathing, circulating blood, maintaining body temperature, repairing cells, and keeping your organs running. It represents the energy you would still spend lying perfectly still in bed all day. Knowing this baseline is the first step toward any sensible calorie target, because every other figure, from weight-loss deficits to maintenance eating, is built on top of it. Enter your sex, age, height, and weight, and the tool returns a personalized resting calorie number in seconds.

Use this calculator when you are planning a diet, recomposition, or fitness program and need a credible starting point instead of a guess. It is genuinely useful for setting a calorie floor: most people should never eat below their BMR for long, because that means consuming only enough to survive while motionless, which is unsustainable and can stall progress. Coaches, dietitians-in-training, and anyone counting calories use BMR to anchor portion sizes, while athletes use it to confirm they are fueling enough. It is also a quick reality check when an app's suggested intake seems suspiciously low or high.

Under the hood the tool uses the Mifflin-St Jeor equation, published in 1990 and recommended by the Academy of Nutrition and Dietetics as the default for healthy adults. For men: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5. For women the final constant is -161 instead of +5, reflecting average differences in body composition. The 166-point spread between the two formulas comes from men typically carrying more lean mass. To get your full daily burn (TDEE), multiply BMR by an activity factor from 1.2 (sedentary) up to 1.9 (extremely active).

This calculator runs entirely in your browser, so the numbers you type, your weight, age, and height, never leave your device or get stored on a server. On accuracy: Mifflin-St Jeor carries an average margin of error around 5 percent for typical adults, better than the older Harris-Benedict formula, but it estimates from population averages and does not measure your actual metabolism. Because it ignores body-fat percentage, results are less precise for very muscular, very lean, or obese individuals. Treat the output as a well-grounded estimate to adjust against real-world results, not a clinical measurement.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is the calories your body burns at complete rest just to stay alive. TDEE (Total Daily Energy Expenditure) is your full daily burn including movement, exercise, and digestion. You get TDEE by multiplying your BMR by an activity factor, typically between 1.2 and 1.9.

Which formula does this BMR Calculator use?

It uses the Mifflin-St Jeor equation, published in 1990 and recommended by the Academy of Nutrition and Dietetics as the default for healthy adults. It is generally more accurate for modern populations than the older Harris-Benedict equation.

Should I eat at my BMR to lose weight?

Almost never. Your BMR is the amount you would burn lying in bed all day, so eating at that level usually creates an extreme, unsustainable deficit once normal activity is added. For fat loss, calculate your TDEE first, then subtract a moderate deficit (often 300-500 calories) from that larger number.

How accurate is the BMR result?

The Mifflin-St Jeor equation has an average error of about 5 percent for typical adults. Because it relies on age, sex, height, and weight rather than measured body composition, it is less accurate for very muscular, very lean, or obese individuals. Use it as a starting estimate and adjust based on your real results.

Can I increase my BMR?

Yes, mainly by building lean muscle, since muscle tissue burns more energy at rest than fat. Each pound of added muscle raises BMR by roughly 6-10 calories per day, so regular strength training can help offset the natural metabolic decline that comes with age.

From our blog

Daily Fat Grams Made Simple: How to Set and Hit Your Target

By the Super Simple Digital Tools Team · Updated June 2026

Fat has spent decades swinging between villain and hero in diet headlines, and that whiplash is exactly why a calculator helps. Instead of arguing about whether fat is good or bad, you can anchor your plan to a clear number. The starting point is always your total daily calories, because fat is expressed as a slice of that total. Once you know roughly how many calories you eat to maintain, lose, or gain weight, the fat question stops being philosophical and becomes arithmetic you can actually act on at the grocery store and the dinner table.

Choosing your percentage is the one judgment call the calculator cannot make for you. A reasonable default for most people is 25 to 30 percent of calories from fat, which lands comfortably inside the 20 to 35 percent window that public-health bodies recommend. If you prefer a higher-carb, lower-fat style of eating, drift toward 20 percent. If you eat low-carb, you will naturally rise toward the top of the range or beyond. The percentage you pick should reflect a way of eating you can sustain, not a number that looks impressive for a week and collapses afterward.

After you have a percentage, the conversion is quick: calories times percentage, divided by nine. Suppose you eat 1,800 calories and target 28 percent fat. That is 1,800 x 0.28 = 504 fat calories, and 504 divided by 9 is 56 grams per day. Keep that figure visible while you log meals, because fat hides in places labels make easy to overlook, including dressings, sauces, cooking oil, baked goods, and cheese. A single tablespoon of oil is around 14 grams, so a couple of generous pours can quietly use up a quarter of your daily allowance.

The number on the calculator tells you how much, but it says nothing about what kind, and the kind is where most of the health payoff lives. Prioritize unsaturated fats from olive oil, avocados, nuts, seeds, and oily fish, which support heart and brain health and supply the essential omega-3 fatty acids your body cannot make on its own. Treat saturated fat as a sub-budget inside your total, ideally under 10 percent of calories, and avoid artificial trans fats entirely. Two diets can hit the same fat-gram target and still differ enormously in their effect on cholesterol and long-term risk.

Finally, use the calculator as a recurring tool rather than a one-time lookup. Recalculate whenever your calorie needs change, such as after losing weight, ramping up training, or shifting your eating style. Run a few what-if scenarios side by side to see how moving from 20 to 35 percent reshapes your daily grams, then sanity-check the result against how full and energetic you feel. The goal is a target that is specific enough to guide real choices yet flexible enough to live with for months, not a rigid figure you dread.

  • Lock in an accurate daily calorie figure first; if your calorie estimate is off, the fat-gram target inherited from it will be off too.
  • Remember each gram of fat is 9 calories, so small extras add up fast. One tablespoon of oil is about 14 grams of fat.
  • Set a separate ceiling for saturated fat, roughly under 22 grams on a 2,000-calorie diet, and fill the rest with unsaturated sources.
  • Do not chase ever-lower fat. Stay at or above 20 percent of calories so you still get essential fatty acids and fat-soluble vitamins.

Read the full guide →

Tool by the Super Simple Digital Tools Team. Reviewed by our editorial team. Free to use, no signup required.

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