BMR Calculator for Seniors — Rate After 60

Basal metabolic rate does fall in later life, but later and for a different reason than most people expect. The Mifflin-St Jeor equation was fitted on adults aged 19 to 78, so older adults were genuinely in the sample. Enter sex, age, weight and height:

The equation’s age term is the wrong shape

The formula subtracts a flat 5 kcal for every year of age, from 19 onward, in a straight line. Reality is not a straight line.

Doubly labeled water measurements spanning ages 8 days to 95 years found four distinct phases: expenditure per unit of fat-free mass accelerates in infancy to about 50% above adult values around age one, declines slowly to adult level by roughly 20, remains stable through adulthood from 20 to 60, and only then declines in older adults. The 2023 Dietary Reference Intakes describe the same trajectory and attribute the late-life fall to decreases in fat-free mass and in organ metabolism.

So the equation charges a 45-year-old for 26 years of decline that the measurements say did not happen, and then applies the same annual rate after 60, when something real does begin. It is a convenient approximation across a wide age range, not a description of what your body did.

What the numbers look like

A woman at 145 lb and 5 ft 4 in — 65.8 kg and 162.6 cm — at three ages:

Age	Mifflin-St Jeor estimate
40	1,313 kcal/day
60	1,213 kcal/day
75	1,138 kcal/day

A man at 175 lb and 5 ft 9 in (79.4 kg, 175.3 cm) at 70 comes out at 794 + 1,096 − 350 + 5 = 1,545 kcal/day.

Read those columns carefully. Every difference between the rows is the age coefficient doing its work at constant weight and height — the equation has been told nothing else. If a 70-year-old has lost fifteen pounds of muscle since 50, the formula will not know, and it will overestimate.

Sarcopenia is the actual mechanism

Fat-free mass accounts for 60 to 80% of the differences in resting energy expenditure between individuals, against about half for body weight alone. Muscle is metabolically expensive tissue. Lose it and the resting floor drops with it — even if the bathroom scale is unchanged, because fat replaced the muscle pound for pound.

That is why a lower number after 70 is not “the metabolism switching off.” It is a body composition change with a name, and unlike age it responds to intervention:

• Resistance training. The most effective way to preserve, and often regain, muscle in later life. Two sessions a week is a meaningful dose.
• Adequate protein, spread across meals rather than concentrated in one.
• Daily movement. Non-exercise activity declines noticeably with age — older adults have been measured performing about 29% less of it than younger ones — and it sits inside the largest changeable slice of the daily total. The BMR vs TDEE page covers where that slice sits.

Where the estimate strains

Three caveats specific to this age group:

1. Above 78 the equation is extrapolating past its sample.
2. With significant sarcopenia it will read high, because it prices the weight without knowing what the weight is made of.
3. The base error still applies. The equation lands within 10% of a measured value in about four adults out of five. On a 1,213 kcal estimate, a 10% band is roughly 1,090 to 1,335.

When the number is not the point

None of this is a screening tool. A calculator output cannot be abnormal — it is arithmetic on four inputs. What deserves medical attention is the clinical picture: unintentional weight loss, falling appetite, new fatigue with cold intolerance, or a rapid change in strength or walking speed. Those get assessed in person, not on this page.

For the general explanation of the equation, see the BMR calculator; for the sex-specific breakdown, the BMR calculator for women.

This content is informational and does not replace evaluation by a physician or registered dietitian, particularly in the presence of unintentional weight loss.