What is BMR, and why shouldn't you eat at that number? Here's a clear explanation of BMR, how to calculate it with the Mifflin-St Jeor equation, and how it differs from TDEE, so you know how much you should actually eat each day.
Contents
What is BMR?
What affects BMR?
How to calculate BMR
What is TDEE?
BMR vs. TDEE at a glance
Should you eat based on BMR or TDEE?
FAQ
What is BMR?
When you start losing weight, you'll hear two terms again and again: BMR and TDEE. They sound similar, and many people mix them up. That's one of the most common reasons calorie targets go wrong from the very first step.
BMR (Basal Metabolic Rate) is the minimum number of calories your body needs to stay alive at complete rest.
Even if you lay in bed all day, your body still burns calories to run its basic functions:
Breathing: taking in oxygen and releasing carbon dioxide
Heartbeat and circulation: pumping blood through your body
Body temperature: keeping you at around 98.6°F (37°C)
Brain and organ function
Example: If your BMR is 1,400 calories, your body needs at least 1,400 calories a day just to function, before walking, working, or exercising.
What affects BMR?
Factor | Effect |
|---|---|
Sex | Men usually have a higher BMR due to more muscle mass |
Age | BMR gradually declines with age |
Height | Taller people have more body surface area and a higher BMR |
Weight | Heavier people need more energy to maintain their body |
Muscle mass | Muscle burns more calories than fat, even at rest |
Worth noting: someone with more muscle usually has a higher BMR than someone of the same weight with more fat. That's a big reason to protect your muscle while losing weight.
How to calculate BMR
The most widely used and reasonably accurate formula for adults is the Mifflin-St Jeor equation.
Metric version
Sex | Formula |
|---|---|
Men | BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5 |
Women | BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161 |
US units version
Sex | Formula |
|---|---|
Men | BMR = (4.536 × weight in lb) + (15.88 × height in inches) − (5 × age) + 5 |
Women | BMR = (4.536 × weight in lb) + (15.88 × height in inches) − (5 × age) − 161 |
Example
A 30-year-old woman, 5'3" (160 cm), 132 lb (60 kg):
BMR = (10 × 60) + (6.25 × 160) − (5 × 30) − 161 BMR = 600 + 1,000 − 150 − 161 BMR = 1,289 calories per day
Important: BMR is not how much you should eat. It's the floor. Eating at your BMR for a long time means you're eating too little.
What is TDEE?
The number you actually need for meal planning is TDEE (Total Daily Energy Expenditure): the total calories your body burns in a day. It includes:
BMR (the base, about 60 to 70% of the total)
Exercise: walking, running, lifting, sports
NEAT (Non-Exercise Activity Thermogenesis): everyday movement like walking around, taking stairs, cleaning, cooking
TEF (Thermic Effect of Food): energy used to digest food, about 10% of the total
Quick TDEE calculation
TDEE = BMR × activity factor
Activity level | Description | Factor |
|---|---|---|
Sedentary | Little or no exercise | × 1.2 |
Lightly active | Exercise 1 to 3 days a week | × 1.375 |
Moderately active | Exercise 3 to 5 days a week | × 1.55 |
Very active | Exercise 6 to 7 days a week | × 1.725 |
Extremely active | Physical job or training twice a day | × 1.9 |
BMR vs. TDEE at a glance
BMR | TDEE | |
|---|---|---|
What it is | Minimum calories at complete rest | Total calories burned in a day |
Includes | Basic life functions | BMR + exercise + NEAT + TEF |
Used for | Understanding your body's floor | Setting how much to eat |
Size | Smaller | Larger (BMR × factor) |
Should you eat based on BMR or TDEE?
TDEE. Whether your goal is to lose, gain, or maintain weight, always start from TDEE.
Goal | TDEE | Intake | Result |
|---|---|---|---|
Lose weight | 2,000 | 1,700 | 300 calorie deficit → weight loss |
Maintain | 2,000 | 2,000 | Balanced → stable weight |
Gain weight | 2,000 | 2,300 | 300 calorie surplus → weight gain |
To find the right deficit, see what is a calorie deficit.
Don't eat below your BMR
Cutting calories below your BMR for a long time can lead to:
Metabolic adaptation: your metabolism slows down
Muscle loss: your body breaks down muscle for energy
Constant fatigue
Faster regain once you stop dieting
Safe zone: a moderate deficit that sits between your BMR and TDEE is the sustainable place to be.
FAQ
What is BMR? BMR is the minimum number of calories your body needs to stay alive at complete rest. It's a floor, not a target.
What's the difference between BMR and TDEE? BMR is the minimum at rest. TDEE is everything you burn in a day, including movement and digestion. Use TDEE to plan how much to eat.
Should I eat at my BMR to lose weight faster? No. Eating at or below BMR for a long time slows your metabolism, costs muscle, and leaves you tired. Create a moderate deficit from TDEE instead.
Which BMR formula is most accurate? Mifflin-St Jeor is considered one of the most accurate for adults. It's still an estimate, and individual results vary.
How can I raise my BMR? Building muscle is the most effective way. Sleeping well, eating enough protein, and avoiding very deep calorie cuts also help.
The bottom line
BMR is the minimum your body needs at rest.
TDEE is what you actually burn each day.
Keep it simple: BMR helps you understand your body. TDEE helps you plan your meals. And don't eat below your BMR just to lose weight faster. A moderate, sustainable deficit is what works long term.
By Khanh Phan