Understanding TDEE and BMR: The Math Behind Calorie Counting
Calculate exactly how many calories your body burns every day using our Calorie Calculator, or read on to understand the science of metabolism.
Whether your goal is to lose weight, build muscle, or simply maintain your current physique, success comes down to a fundamental law of thermodynamics: energy balance. If you consume more calories than you burn, you gain weight. If you burn more than you consume, you lose weight.
But how do you know exactly how many calories you burn? It starts with two key metrics: BMR and TDEE.
Basal Metabolic Rate (BMR)
Your Basal Metabolic Rate (BMR) is the number of calories your body requires to accomplish its most basic (basal) life-sustaining functions. This includes breathing, circulating blood, cellular repair, and brain function.
If you lay in bed all day and didn't move a single muscle, your BMR is the amount of calories you would burn just staying alive. For most adults, BMR accounts for about 60-75% of total daily calorie expenditure.
The most widely accepted mathematical formula to calculate BMR is the Mifflin-St Jeor Equation:
- Men:
(10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5 - Women:
(10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161
Total Daily Energy Expenditure (TDEE)
While BMR measures what you burn doing nothing, your Total Daily Energy Expenditure (TDEE) is an estimate of how many calories you burn when exercise and daily movement are factored in.
To calculate TDEE, you multiply your BMR by an Activity Multiplier:
| Activity Level | Multiplier | Description | |----------------|------------|-------------| | Sedentary | BMR x 1.2 | Little or no exercise, desk job. | | Lightly Active| BMR x 1.375 | Light exercise or sports 1-3 days a week. | | Moderately Active| BMR x 1.55 | Moderate exercise or sports 3-5 days a week. | | Very Active | BMR x 1.725 | Hard exercise or sports 6-7 days a week. | | Extra Active | BMR x 1.9 | Very hard daily exercise and a physical job. |
Example: If a woman has a BMR of 1,400 calories and works a desk job but goes for light jogs twice a week (Lightly Active), her TDEE is 1,400 x 1.375 = 1,925 calories.
To maintain her current weight, she should eat exactly 1,925 calories a day.
The 3,500 Calorie Rule
A long-standing rule in nutrition science is that one pound of body fat contains approximately 3,500 calories of stored energy.
Therefore, to lose 1 pound of fat per week, you need to create a caloric deficit of 3,500 calories over the course of seven days.
3,500 / 7 days = 500 calories per day.
By eating 500 calories below your TDEE every day, you will lose roughly one pound per week, which doctors consider a safe and sustainable rate of weight loss.
FAQ
Does building muscle increase my BMR? Yes. Muscle tissue is metabolically more active than fat tissue. Building muscle through resistance training permanently increases your BMR, meaning you burn more calories even when you are resting.
Why did my weight loss plateau? As you lose weight, your BMR drops (because a smaller body requires fewer calories to sustain itself). If you lose 20 pounds, your TDEE is now much lower than when you started. You must recalculate your TDEE and adjust your caloric intake to continue losing weight.
Stop guessing your metabolic rate. Get precise, personalized daily calorie targets using the CalcUnit Calorie Calculator.