How to Estimate your Total Daily Energy Expenditure

Your body’s Total Daily Energy Expenditure (TDEE) is the estimate of how many calories your body burns in a 24-hour period. Knowing this information is useful, since health and fitness experts tell us that caloric intake above TDEE will likely lead to weight gain, while caloric intake below TDEE will likely lead to weight loss. (Note: “Weight” is not the same as “Fat.” One should avoid losing muscle in any weight loss program.)

Section 1.4 in The Calculus of Happiness discusses the research showing that one can accurately estimate TDEE using three components: (1) resting metabolic rate (RMR), (2) an “activity factor” that approximates how many calories you burned doing exercise over the 24-hour period, and (3) how many calories C you ate during the 24-hour period. The reasonably accurate formula that results is:

Here are some typical values for the Activity Factor:

• Little to no physical activity: 1.2

• Light-intensity exercise 1-3 days/week: 1.4

• Moderate-intensity exercise 3-5 days/week: 1.5

• Moderate- to vigorous-intensity exercise 6-7 days/week: 1.7

• Vigorous daily training: 1.9

Feel free to use these and the calculator below to estimate your own TDEE.

Limitations

The resting metabolic rate is the largest contributor to TDEE, and as the link in the calculator discusses, it is a large source of error (possibly even 10%). The Activity Factor is also a rough approximation of one’s actual daily exercise level. Finally, despite our best efforts to track caloric intake, food labels are not 100% accurate. These suggest possibly large errors (5%-20%) in the TDEE estimate generated in the calculator. There are ways to measure your TDEE in a lab, but they tend to be time-consuming and expensive. The estimate above is free and reasonably accurate.