What Is TDEE? BMR vs TDEE and How to Calculate Yours

Key takeaways

• Resting burn, or BMR, is a little under 60 percent of TDEE for a typical adult, and the rest goes to digesting food and moving around.¹
• Calculator equations are a starting guess, since errors for single people can still be large.⁷
• Glycogen is stored with 3 to 4 parts water, so a short window misreads water swings. Four weeks of complete food logs set against your weight trend give you your real number.¹³⁸
• The 3,500 calorie rule assumes your burn stays the same as you lose weight, and it overestimated actual weight loss in seven tightly controlled studies.¹⁰¹¹

What is the difference between BMR and TDEE?

TDEE, or total daily energy expenditure, is every calorie your body burns in a day. Resting burn, or BMR, is the biggest part, a little under 60 percent for a typical adult, and the rest goes to digesting food and moving around. A calculator gives you a starting guess. Four weeks of complete food logs set against your weight trend give you your real number.¹⁸

BMR, your basal metabolic rate, is what your body burns lying still, awake, and fasted. It keeps your heart, brain, kidneys and liver running. RMR, your resting metabolic rate, is measured under slightly looser conditions, and most people use the two words for the same thing.¹⁴

TDEE is BMR plus everything else you do in a day. Researchers describe the gap between them with a ratio called PAL, which is total burn divided by resting burn. In adults the average PAL is about 1.7 to 1.8, and lifestyles people can keep up range from about 1.1 to 2.5. At a PAL of 1.7, resting burn is about 59 percent of the day's total.¹

Which organs burn the most at rest?

Small organs do most of the resting work. Per kilogram per day, the heart and kidneys burn about 440 calories, the brain about 240 and the liver about 200. Skeletal muscle burns about 13, and fat tissue about 4.5. Wang's team tested values first proposed by Elia in 1992 against MRI scans and measured resting burn, and they held up in adults, running about 3 percent lower after age 50.⁴

That works out to roughly 6 calories per pound of muscle per day at rest, and about 2 per pound of fat.⁴

How much does food digestion add?

Digestion costs differ by nutrient. Measured values are 20 to 30 percent of the calories in protein, 5 to 10 percent for carbohydrate, 0 to 3 percent for fat, and 10 to 30 percent for alcohol. On a mixed diet the total lands at 5 to 15 percent of the day's burn. The size of this part depends on how much you eat and what it is made of.²

Why does TDEE differ so much between people?

Lean mass is the best single predictor of resting burn. Everyday movement does much of the rest. In one study, 16 adults ate 1,000 extra calories a day for 8 weeks. About two-thirds of the rise in their daily burn came from NEAT, and differences in NEAT explained a 10-fold spread in how much fat they gained.⁶³

Age matters less than many people think. In doubly labeled water data on over 6,400 people, burn adjusted for lean mass stayed stable from about age 20 to 60 and then declined.⁵

How do TDEE calculators work?

Most calculators estimate BMR with an equation, then multiply by an activity factor. The usual equation is Mifflin-St Jeor, built from measured resting burn in 498 healthy adults.⁶

A review of the common equations found Mifflin-St Jeor was the most likely to land within 10 percent of measured resting burn, in people with and without obesity. The same review warned that errors for single people can still be large, and that older adults and some ethnic groups were underrepresented in the data.⁷

Ten percent sounds small. On a 2,500 calorie day it is 250 calories either way, before the activity factor adds its own guess. That is why a calculator is a starting point and your log is the check.⁷

• For men, BMR equals 10 times weight in kilograms, plus 6.25 times height in centimeters, minus 5 times age, plus 5.⁶
• For women, BMR equals 10 times weight in kilograms, plus 6.25 times height in centimeters, minus 5 times age, minus 161.⁶

How do you calculate your real TDEE?

Energy balance does the work. If you know what you ate and how your weight moved, you can solve for what you burned. This is the same balance that Hall's weight-change model and its online simulator are built on.⁸

The formula is this. Multiply pounds lost by 3,500 and divide by 21. TDEE is about your average daily intake plus that result.⁸

If your weight went up, subtract instead of adding.

Here is a made-up example. Someone averages 2,200 logged calories a day. Their weekly average drops 1.5 pounds between week 1 and week 4. That is 1.5 times 3,500, or 5,250 calories, divided by 21 days, or 250 a day. Their TDEE is about 2,450.⁸

The 3,500 figure is a rough number for the energy in a pound of lost weight. It is fine here because over a short window the result barely moves if you change it. In one study, a pound of weight lost held closer to 2,700 calories once the first weeks had passed, and less before that. Using that in the example gives about 2,390 instead of 2,450. The long-run problem with the 3,500 rule is a different one, covered below.¹²

• Log everything you eat and drink for 4 weeks, including cooking oil, sauces and drinks.
• Weigh yourself each morning, same scale, same routine.
• Average your first 7 weigh-ins and your last 7. In a 4-week log those two averages sit 21 days apart.
• Find your average daily intake across the 4 weeks.
• Use this formula.

Why does it take about 4 weeks?

Water moves the scale faster than fat does. Glycogen, the carbohydrate stored in your liver and muscles, is stored with 3 to 4 parts water. When stores fill or empty, the scale shifts with no change in body fat.¹³

When people start eating less, the energy content of each kilogram lost is low at first and rises over the first month or more. In one study it went from about 4,900 calories per kilogram at week 4 to about 6,000 at week 6, then held steady.¹²

The arithmetic shows why a short window misleads. Say water moves your weekly average by 1 pound. Over 7 days, the formula reads that as 500 calories a day. Over 21 days, it reads it as about 170. The longer the window, the less a water swing distorts the answer.¹³

The log has to be complete too. In one study of people whose weight wasn't moving on a reported low intake, people reported eating 47 percent less than they actually ate, on average, while their resting burn was within 5 percent of predicted. Missed items make the back-calculated TDEE come out low.¹⁴

Is the 3,500 calorie rule wrong?

Partly. The number itself is close for some people. For people with more than about 30 kilograms of body fat, 3,500 calories per pound roughly matches the energy in the weight they lose. For leaner people it overstates the deficit needed, because more of what they lose is lean tissue. Fat holds about 9,400 calories per kilogram and lean tissue about 1,800, roughly 5 times less.⁹⁸

The bigger error is that the rule assumes your burn stays the same as you lose weight. It doesn't. Hall and Chow call this failure to account for changing energy balance the rule's most serious error. Compared with seven tightly controlled weight loss studies, the rule overestimated actual weight loss.¹⁰¹¹

Hall's model gives a better rule of thumb. For an average adult with overweight, each 10 calories a day of change in intake leads to about 1 pound of eventual weight change, half of it in about a year and 95 percent in about 3 years. Put the other way, a lighter body needs fewer calories to stay where it is, so your TDEE drifts down as you lose.⁸

How accurate is Apple Watch calorie burn?

Not very. Heart rate is close. Calories are not.¹⁵¹⁶

Extra exercise also doesn't add up one for one. In 332 adults, daily burn rose with activity at low levels but leveled off at higher levels. A watch's total is best used as a trend. Your intake and weight trend tell you more about your real TDEE.¹⁸

• In 22 adults, Apple Watch and three other wrist devices measured heart rate within 1 to 9 percent, but energy burn was off by 9 to 43 percent. All four read low in that lab test.¹⁵
• In 60 adults wearing seven devices, none got energy burn within 20 percent. Apple Watch had the lowest overall error, and errors were larger at higher BMI.¹⁶
• A review of 158 studies found no wearable brand measured energy burn accurately.¹⁷

How to track it

The method needs two things logged every day, food and morning weight. Log food when you eat it so oils, drinks and bites don't slip through. Weigh at the same time each morning and look at weekly averages, not single days. Every 4 weeks, run the formula again with fresh numbers, since your TDEE moves as your weight does.⁸

TrueCal lets you type or say a meal in plain words and keeps a weight trend next to your food log, so both halves of the formula are in one place when you want to check.

Common myths

• Myth, 3,500 calories always equals one pound. It's a rough short-window figure. Over months it overstates loss because burn falls as weight falls.¹⁰
• Myth, metabolism slows in your 30s. Adjusted for lean mass, daily burn held steady from 20 to 60.⁵
• Myth, a pound of muscle burns 50 calories a day. Resting muscle burns about 6 calories per pound.⁴
• Myth, your watch total is your TDEE. No wrist device in the studies above got energy burn within 20 percent.¹⁶
• Myth, every exercise calorie adds to your daily burn. Total burn levels off at higher activity.¹⁸

A note on medical advice

This article is for general information and isn't medical advice. Talk with your clinician about your own situation.

Worked example

At a PAL of 1.7, resting burn is the day's total divided by 1.7. On a 2,500 calorie day, 2,500 divided by 1.7 is about 1,470 calories, about 59 percent of the total.¹

A closer look

In one study of people whose weight wasn't moving on a reported low intake, people reported eating 47 percent less than they actually ate, on average, while their resting burn was within 5 percent of predicted. Missed items make the back-calculated TDEE come out low.¹⁴

Questions and answers

Related guides

• TDEE calculator
• Calorie deficit calculator
• Weight loss plateaus
• The slow metabolism myth
• How TrueCal works

Sources

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