Build a daily energy estimate from the Mifflin–St Jeor equation, compare activity assumptions, and calculate an illustrative calorie deficit without confusing resting energy with a universal minimum intake.
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The calculation
Resting estimate = 10w + 6.25h − 5a + s; estimated TDEE = resting estimate × A; illustrative intake = estimated TDEE − deficit. w: kg, h: cm, a: years, s: +5 male or −161 female.
Worked example
For a hypothetical adult using the male equation: w = 80 kg, h = 180 cm, a = 35 years. Resting estimate = 800 + 1,125 – 175 + 5 = 1,755 kcal/day. With the assumed factor A = 1.55, estimated TDEE = 1,755 x 1.55 = 2,720.25, or about 2,720 kcal/day. An illustrative deficit of 300 kcal/day gives about 2,420 kcal/day. Using A = 1.20 instead gives 2,106 kcal/day, a difference of about 614 kcal/day.
Educational adult energy estimates, not an individual diet prescription or universal minimum. The original Mifflin equation estimates resting energy expenditure; strict basal metabolic rate is measured under standardized conditions. Activity factors are assumptions, not directly measured energy expenditure. Seek individual guidance for clinical circumstances; not for children, pregnancy or breastfeeding.
Video chapters
- 0:00 — Calorie needs are an energy budget
- 0:23 — Keep the inputs and units straight
- 0:53 — Build the resting-energy example
- 1:22 — Expand rest into a whole day
- 1:45 — Activity assumptions change the answer
- 2:07 — A deficit is subtraction, not a floor
- 2:32 — An estimate cannot prescribe a minimum
- 2:56 — Rest, daily total, then the difference
Read the full transcript
There is no single minimum calorie intake that suits everyone. Start by separating two ideas: energy used at rest, and energy used over a whole day. Resting energy supports functions such as breathing and circulation. Movement and processing food add to the daily total. Let us calculate an example, then see what the estimate can and cannot tell us.
A common equation is Mifflin–St Jeor. It estimates resting energy expenditure, often labeled BMR in calculators. Use weight in kilograms, height in centimeters, and age in years. The simplified equation is ten times weight, plus six point two five times height, minus five times age, plus a sex-specific constant: plus five for the male equation, or minus one hundred sixty-one for the female equation.
Our hypothetical adult is male, eighty kilograms, one hundred eighty centimeters tall, and thirty-five years old. Ten times eighty is eight hundred. Six point two five times one hundred eighty is one thousand one hundred twenty-five. Five times thirty-five is one hundred seventy-five. Add the first two terms, subtract the age term, and add five. The resting estimate is one thousand seven hundred fifty-five kilocalories per day.
To estimate total daily energy expenditure, multiply the resting estimate by an assumed activity factor. For this example, use one point five five. One thousand seven hundred fifty-five times one point five five is two thousand seven hundred twenty point two five. Round that to about two thousand seven hundred twenty kilocalories per day. This is an estimated maintenance level, not a precise measurement.
Keep the same person and resting estimate, but use a factor of one point two. The daily estimate becomes two thousand one hundred six. That is about six hundred fourteen calories lower than the first estimate. An activity label is a rough assumption. It does not measure your daily movement, and exercise frequency alone cannot capture every part of your energy use.
A calorie deficit means intake is below total daily expenditure. As an arithmetic example, subtract three hundred from the estimated maintenance level of about two thousand seven hundred twenty. That gives about two thousand four hundred twenty calories per day. The three hundred is an illustrative choice, not a personal recommendation. Resting expenditure is also not a rule that determines the minimum you should eat.
Individual needs and nutritional adequacy matter. These adult estimates are not intended for children, or for pregnancy and breastfeeding. Medical conditions, medications, and eating-disorder history can also require individual guidance. A clinician or registered dietitian can help interpret the estimate and choose an appropriate plan. Changes in body weight and activity can change energy needs over time.
Remember the sequence. First, use consistent units to estimate resting energy. Second, apply an appropriate activity assumption to estimate maintenance. Third, calculate any difference from that daily total. In our example: seventeen fifty-five at rest, about twenty-seven twenty for maintenance, and about twenty-four twenty after an illustrative three-hundred-calorie deficit. Keep the assumptions visible. A calculated estimate is a starting point, not a universal minimum intake.
Sources
- Mifflin et al. — Original resting-energy prediction equation (1990)
- FAO/WHO/UNU — Human energy requirements and definitions
- NIDDK — Adult energy planning and limitations