BMR and TDEE are the two numbers behind almost every calorie target you will ever see, and they get mixed up constantly. BMR (basal metabolic rate) is the energy your body burns just to stay alive at complete rest. TDEE (total daily energy expenditure) is BMR plus everything else you do in a day: walking, working out, fidgeting, and digesting food. Confusing the two leads to a common and serious mistake: eating close to your BMR when trying to lose weight, which is far too low for almost anyone. This guide covers the exact formulas, a full worked example, and how to pick the activity level that gets your TDEE right, backed by the tdee-calculator and bmr-calculator.
What is BMR and how do you calculate it
BMR is the number of calories your body needs to run its basic functions, breathing, circulation, cell repair, and organ activity, while lying still and fully at rest. It does not include any movement, exercise, or digestion. The current standard formula for estimating it is the Mifflin-St Jeor equation, published in 1990, which replaced the older Harris-Benedict equation because it more closely matches measured resting metabolic rate in modern populations.
Men: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age + 5
Women: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age - 161
Notice that weight, height, and age are the only inputs. Weight carries the most influence because more body mass, particularly muscle, burns more energy at rest. The formula is a population average built from statistical studies, so it will not match your exact metabolism, but it is close enough for almost everyone to use as a starting point for setting calorie targets. If you would rather skip the arithmetic, the bmr-calculator runs this formula for you and returns your BMR instantly.
What is TDEE and how is it different from BMR
TDEE takes your BMR and multiplies it by an activity factor that accounts for everything BMR leaves out: walking around, workouts, standing at your desk, and the extra energy your body spends digesting food. This is the number that actually represents how many calories you burn in a typical day, and it is almost always meaningfully higher than BMR, often by 20 to 90% depending on how active you are.
TDEE = BMR x activity multiplier
The activity multipliers are standardized into five tiers:
| Activity level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise | 1.2 |
| Lightly active | Light exercise 1 to 3 days/week | 1.375 |
| Moderately active | Moderate exercise 3 to 5 days/week | 1.55 |
| Very active | Hard exercise 6 to 7 days/week | 1.725 |
| Extremely active | Very hard exercise plus a physical job | 1.9 |
These tiers broadly line up with the physical activity guidelines the CDC publishes for adults, which frame activity in terms of weekly minutes of moderate or vigorous exercise rather than a single multiplier, but map onto the same underlying idea: more regular movement raises your total energy needs well above BMR.
How to calculate your TDEE step by step
Here is a full worked example using a real set of numbers, verified with exact arithmetic rather than rounded intermediate steps.
Person: a 30-year-old woman, 65 kg, 165 cm tall, moderately active.
Step 1: Calculate BMR with Mifflin-St Jeor (women's formula).
BMR = 10 x 65 + 6.25 x 165 - 5 x 30 - 161 BMR = 650 + 1,031.25 - 150 - 161 BMR = 1,370.25, rounded to about 1,370 calories per day
Step 2: Apply the activity multiplier.
She works out 4 days a week at a moderate intensity, which puts her in the moderately active tier (multiplier 1.55).
TDEE = 1,370.25 x 1.55 = 2,123.9, rounded to about 2,124 calories per day
Step 3: Compare the two numbers.
Her BMR of 1,370 calories is what her body would burn lying in bed all day. Her TDEE of 2,124 calories is what she actually burns given her real activity level, a difference of roughly 754 calories, all coming from movement, exercise, and digestion that BMR does not count. If she wanted to lose weight, her calorie target should be built from the 2,124 TDEE figure (for example, a moderate 500-calorie deficit would put her around 1,624 calories a day), never from the 1,370 BMR figure. For comparison, the same height, weight, and age for a man using the men's formula (BMR = 10 x 65 + 6.25 x 165 - 5 x 30 + 5 = 1,536.25) would produce a higher BMR and TDEE, because the formulas differ by a constant offset (+5 for men versus -161 for women) that reflects average differences in body composition between sexes.
Which activity level should you pick
Picking the right multiplier matters more than almost any other input, because it is a straight multiplication: overestimating your activity level inflates your TDEE and can stall weight loss, while underestimating it leaves you under-eating and unnecessarily hungry.
- Sedentary (1.2): a desk job, minimal walking, no structured exercise.
- Lightly active (1.375): light exercise or sports 1 to 3 days a week, or a job that involves some walking.
- Moderately active (1.55): moderate exercise or sports 3 to 5 days a week.
- Very active (1.725): hard exercise or sports 6 to 7 days a week.
- Extremely active (1.9): very hard daily training combined with a physically demanding job, such as construction or manual labor.
Most people overestimate how active they really are, especially when a single weekly gym visit gets rounded up to "very active." If you are genuinely unsure which tier fits, choose the lower one, track your weight for two to three weeks at the resulting calorie target, and adjust from there based on what actually happens. This trial-and-adjustment approach is more reliable than any formula alone, because it accounts for your individual metabolism rather than a population average.
Is BMR alone a safe calorie target
No. BMR is not a calorie target, it is a floor. It represents the absolute minimum energy your body needs just to keep its organs running at rest, and eating at or below that level for any length of time is considered unsafe and counterproductive by mainstream nutrition guidance. Extremely restrictive diets that dip under BMR tend to backfire in several ways: they can slow metabolic rate as the body tries to conserve energy, increase the proportion of weight lost from muscle rather than fat, disrupt hormone regulation, and make the diet so difficult to sustain that any short-term loss is quickly regained.
The safer, evidence-backed approach for weight loss is a moderate deficit below TDEE, not below BMR. The NIH's National Institute of Diabetes and Digestive and Kidney Diseases publishes body weight planning guidance built on exactly this principle: energy balance is calculated against total daily expenditure, and sustainable loss comes from a moderate, consistent deficit maintained over time rather than a drastic short-term cut. A common, reasonable starting point is a 500-calorie deficit below TDEE, which targets roughly one pound of fat loss per week without dropping intake anywhere near BMR for most people.
BMR versus RMR: a related but distinct measurement
You will also see the term RMR, or resting metabolic rate, used alongside BMR, and the two are often treated as interchangeable in everyday calculators even though they are measured differently in a clinical setting. True BMR requires strict conditions: an overnight fast, a full night's rest, lying completely still, and a temperature-controlled room, with no digestion or movement in the preceding hours. RMR is measured under more relaxed conditions, typically without the strict overnight fast, and tends to come out 5 to 10% higher than a true BMR reading as a result. In practice, home and online BMR calculators, including the Mifflin-St Jeor formula used throughout this guide, actually estimate something closer to RMR conditions, since almost nobody testing at home replicates a full clinical BMR protocol. The distinction rarely changes what you should do with the number: whichever term is used, it is still just the resting-energy baseline that TDEE builds on top of, and it is still not the number to eat.
Putting it together
BMR tells you what your body burns at rest. TDEE tells you what your body actually burns in a real day, and it is the number that should anchor any calorie target, whether you are cutting, maintaining, or building muscle. Calculate your BMR with the bmr-calculator, pick the activity tier that honestly matches your week, and let the tdee-calculator do the multiplication for you. From there, the macro-calculator can split your TDEE-based target into protein, carbs, and fat, so you go from a single formula to a full day of eating in a couple of clicks.