BMR vs TDEE: What's the Difference and Which Should You Use?

BMR (basal metabolic rate) is the energy your body uses at complete rest just to stay alive: breathing, circulation, keeping warm, repairing cells. TDEE (total daily energy expenditure) is BMR plus everything else you burn in a day, from digesting food to walking, working and exercising. For setting a calorie target you use TDEE, because that is what you actually spend; BMR is only the foundation it is built on.

Below you will find what each number means, how to calculate BMR and TDEE, and how to use them without being misled by false precision.

BMR vs TDEE at a glance

	BMR	TDEE
What it measures	Energy for basic body functions at rest	All the energy you use in 24 hours
Includes movement?	No	Yes: exercise, daily activity, work
Includes digestion?	No	Yes
Typical size	About 45 to 70% of TDEE	100%
Main use	Starting point for estimates	Setting your calorie target

The FAO/WHO/UNU expert report on human energy requirements states that, depending on age and lifestyle, BMR represents 45 to 70 percent of daily total energy expenditure. In other words, for most people the “at rest” part is the biggest single slice of the day, but not the whole pie.

What is BMR (basal metabolic rate)?

BMR is the minimum energy needed to keep your body running when you are lying still, awake, in a comfortable temperature and have not eaten for several hours. It covers the work of your heart, lungs, brain, liver, kidneys and every other tissue.

It depends mainly on:

• Body size. Larger bodies need more energy.
• Body composition. Fat-free mass, which includes muscle and organs, is the strongest single predictor. In the study behind the Mifflin-St Jeor equation, fat-free mass alone explained more of the variation in resting energy than body weight did.
• Sex. Men usually have a higher BMR, largely because of greater size and muscle.
• Age. BMR tends to decline slowly through adulthood.

BMR vs RMR

You will also see RMR (resting metabolic rate) or REE (resting energy expenditure). RMR is usually measured under slightly less strict conditions than BMR, but in everyday use the two are close enough to be treated as the same thing. The Mifflin-St Jeor equation technically predicts resting energy expenditure.

What is TDEE (total daily energy expenditure)?

TDEE has three main parts:

1. Basal metabolism (BMR): the largest part for most people.
2. The thermic effect of food: the energy used to digest, absorb and store what you eat. The FAO/WHO/UNU report puts it at about 10% of BMR over 24 hours on a mixed diet. It is real but small, which is why “metabolism-boosting foods” make little practical difference.
3. Physical activity: everything from planned workouts to walking to the bus, cooking, standing and fidgeting. The FAO/WHO/UNU report calls this the most variable component and, after BMR, the second largest.

That third part is where people differ most. Two people with the same BMR can end up with TDEEs that are hundreds of calories apart simply because one walks 3,000 steps a day and the other 12,000. If you want to increase your daily burn, everyday movement is the lever you control most. Our guide on how many steps a day to lose weight goes into this.

How to calculate BMR and TDEE

Step 1: Calculate BMR with Mifflin-St Jeor

A systematic review of the most common prediction equations found Mifflin-St Jeor to be the most reliable, estimating resting metabolic rate within 10% of the measured value in more people than the alternatives. The formulas are:

• Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
• Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5

The original paper also found that the older Harris-Benedict equations from 1919 overestimated measured resting energy by about 5%.

Step 2: Multiply by an activity factor to get TDEE

TDEE = BMR × activity factor. Calculators usually offer factors like these:

Activity level	Factor
Sedentary (little exercise)	1.2
Lightly active (1 to 3 days a week)	1.375
Moderately active (3 to 5 days a week)	1.55
Very active (6 to 7 days a week or physical job)	1.725

In research, the same ratio is called the physical activity level (PAL). The FAO/WHO/UNU report classifies lifestyles as sedentary or lightly active at PAL 1.40 to 1.69, active at 1.70 to 1.99 and vigorously active at 2.00 to 2.40, and notes that values above 2.40 are difficult to maintain for long.

Worked example

A 35-year-old woman, 165 cm, 70 kg:

• BMR = 700 + 1,031 − 175 − 161 = about 1,395 kcal

Her TDEE depends heavily on activity:

Activity level	Calculation	TDEE
Sedentary	1,395 × 1.2	about 1,675 kcal
Lightly active	1,395 × 1.375	about 1,920 kcal
Moderately active	1,395 × 1.55	about 2,160 kcal
Very active	1,395 × 1.725	about 2,405 kcal

Same body, a difference of about 730 kcal a day between the lowest and highest activity level. This is why picking the right activity factor matters more than the decimal places in the BMR formula.

For a man of 40, 180 cm and 85 kg, BMR = 850 + 1,125 − 200 + 5 = 1,780 kcal, and at a moderate activity level his TDEE is about 1,780 × 1.55 = 2,760 kcal.

Which number should you eat: BMR or TDEE?

Use TDEE as your maintenance number, then adjust for your goal:

• Maintenance: eat around your TDEE.
• Weight loss: eat below your TDEE. A deficit of about 500 kcal a day is a common starting point; see our guide to the calorie deficit.
• Weight gain: eat a little above your TDEE.

A widespread piece of advice says “never eat below your BMR”. The reasoning is sensible, but the rule itself is a bit misleading. Your BMR is part of your TDEE, not a separate budget, and your body does not switch into a special mode when you cross that line. The real point is simpler: for most people, eating at or below BMR means a very large deficit, which is hard to sustain and makes it difficult to meet protein and micronutrient needs. As a practical floor, stay above about 1,200 kcal a day for women and 1,500 kcal for men unless you are under medical supervision.

This is also how the PixNutri calorie goal works: it estimates your resting energy with Mifflin-St Jeor, multiplies it by the activity factor you choose, then subtracts 500 kcal for weight loss (never below those floors) or adds 300 kcal for gain. If you connect Apple Health or Health Connect, part of the active energy your phone or watch records is added to that day’s goal.

Why your calculated TDEE is only an estimate

Treat any TDEE figure as a first guess with a margin of error of at least ±10%.

• Equations are averages. The systematic review warns that errors can be meaningful for individuals, and that older adults and some ethnic groups were underrepresented in the studies.
• Activity is hard to self-rate. Most people do not know whether they are “lightly” or “moderately” active until they track it for a while.
• Your TDEE changes as you change. Lose 10 kg and both your BMR and the energy cost of moving your body go down.

Metabolic adaptation

When you lose weight, energy expenditure usually falls a bit more than the change in body size alone would predict. A well-known NIH follow-up study of 14 contestants from the “Biggest Loser” TV competition found that after extreme weight loss, resting metabolic rate was still about 500 kcal a day lower than expected six years later. That was an extreme situation, with very rapid loss of about 58 kg on average, so it does not describe a typical moderate diet. The lesson for everyday life is milder: expect your TDEE to drift down as you lose weight, and recalculate as you go. Our guide on the weight loss plateau explains what to do when progress slows.

How to find your real TDEE

The practical way to pin down your TDEE is to let your body tell you:

1. Start with the calculated TDEE.
2. Eat close to that number for 2 to 3 weeks, logging honestly, including drinks and cooking fat.
3. Track your weight several times a week and compare weekly averages.
4. If your weight is stable, that intake is your real maintenance. If it rises or falls, adjust by 100 to 200 kcal and repeat.

Consistent logging is the hard part. A photo-based tracker like PixNutri can help: you snap a meal, get an AI estimate of calories and macros, and review or edit the values and portion before saving. Photo estimates are approximate, especially for oils and sauces you cannot see, so a quick check keeps your data useful.

For more on setting your starting number, see how many calories you should eat a day.

FAQ

Is BMR the same as metabolism?

Not quite. BMR is one part of your metabolism: the energy used at rest. Your total metabolism for the day, TDEE, also includes digestion and all physical activity.

What is a normal BMR?

It varies with size, sex, age and body composition. For the example adults above it ranges from about 1,400 kcal for a 70 kg woman to about 1,780 kcal for an 85 kg man, but your own figure may be quite different.

Should I eat less than my BMR to lose weight?

Usually there is no need. A deficit of around 500 kcal below TDEE produces steady loss for most people, and staying above about 1,200 kcal (women) or 1,500 kcal (men) keeps the diet more nutritious and sustainable.

How accurate are TDEE calculators?

They are reasonable starting points. The best equation is within about 10% for many, but not all, people. Your weight trend over a few weeks is the most reliable check.

Can I increase my BMR?

Building and keeping muscle through strength training helps maintain fat-free mass, the main driver of BMR. Do not expect dramatic changes; for most people, moving more during the day has a bigger effect on TDEE.