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Desk work, driving, little deliberate exercise. PAL 1.4–1.69.
Mifflin-St Jeor is the default; the 1984 Harris-Benedict revision is here to compare against.
1,904 – 2,299 kcal
A day. The spread is the published activity band, not a rounding error.
An estimate, not medical advice, and not a prescription for what to eat. Mifflin-St Jeor was fitted on 498 general-population adults, so it misestimates anyone whose body composition is unusual for their height and weight — it reads low for a muscular athlete and was within 10% for only 70% of the obese adults in the review that made it the standard. Measured resting metabolism varies by a few hundred calories between two people of identical size. Treat the number as a starting point and adjust it against what actually happens over a few weeks.
The activity spread comes from the FAO/WHO/UNU bands, which are published as ranges — sedentary 1.40–1.69, active 1.70–1.99, vigorous 2.00–2.40 — rather than as the single multipliers most calculators use. Goals are converted at roughly 3,500 kcal per pound of fat, a 1958 rule of thumb that overestimates real loss over months, most of all for people who are already lean. Anyone planning a large or rapid change, pregnant or breastfeeding, under 18, or managing a medical condition should get a target from a clinician instead.
Basal metabolic rate is what your body spends doing nothing at all: keeping a heart beating, a brain lit and a temperature held. It is the largest single component of what most people burn in a day. Multiply it by a factor for how much you move and you get total daily energy expenditure — the figure that actually matters if you are trying to hold a weight, lose one or put one on.
For a woman of that size, Mifflin-St Jeor returns 1,360 kcal at rest. The 1984 Harris-Benedict revision, run on the same body, returns 1,421 — a 61 kcal disagreement between two respectable equations, which is worth seeing before you treat any single figure as exact.
At a sedentary activity level, that resting figure becomes a maintenance range of 1,904 to 2,299 kcal a day. Ask for a pound a week of loss and the target drops by 500 a day, to 1,404 to 1,799. Move the same body to a vigorously active life and maintenance rises to 2,721 to 3,265 — a bigger swing than any choice of equation will ever produce.
A 2005 systematic review in the Journal of the American Dietetic Association compared the four equations in common clinical use against metabolism measured by indirect calorimetry. Mifflin-St Jeor came within 10% of the measured value more often than any other and had the narrowest error range, which is why it became the standard recommendation.
The same review is the reason to be careful with it. That accuracy was 82% of non-obese adults and only 70% of obese ones, so nearly a third of the second group were out by more than a tenth. It was fitted on 498 general-population adults, and it has no way to know you carry unusual muscle.
The familiar ladder of activity multipliers — 1.2, 1.375, 1.55, 1.725, 1.9 — is repeated everywhere and traceable to nothing. The joint FAO, WHO and UNU expert consultation on human energy requirements does publish activity levels, but as bands: 1.40 to 1.69 for sedentary and light lifestyles, 1.70 to 1.99 for active ones, 2.00 to 2.40 for vigorous. This tool uses the bands as published, so the output is a spread rather than a falsely exact figure.
Goals are converted at roughly 3,500 kcal per pound of fat, a rule Max Wishnofsky published in 1958. Kevin Hall showed in 2008 that it overstates what a sustained deficit delivers, and most of all for people who were already lean, because the body adapts as it shrinks. Expect the first weeks to track and the later ones to fall behind.
It is a threshold worth noticing rather than a hard rule, but a target under the resting figure means the deficit comes out of everything the body does above lying still. Very low intakes are used clinically, under supervision, for good reasons. If a target here lands that low, take it to a dietitian rather than a spreadsheet.
Almost always because it used a different equation, a different activity multiplier, or both. Harris-Benedict and Mifflin-St Jeor differ by tens of calories at the same body size, and multiplier ladders differ by hundreds. None of them is measuring anything about you; they are all regressions fitted to other people.
Think about the whole week, not the hardest session in it. Most people with desk jobs land in the sedentary band even when they train several times a week, because an hour of exercise is small against fifteen waking hours of sitting. If two bands seem plausible, take the lower one and adjust from what actually happens.
Poorly. Prediction equations are built on general populations and tend to underestimate people carrying a lot of lean mass or training at high volume. Athletes are better served by measured metabolic testing, or by tracking intake against weight over a few stable weeks and reading the answer off their own data.