Every calculator gives you a number. None of them tell you where it stops.
Maintenance, deficit, protein floor, rate of loss. Then the part the others skip: your maintenance falls as you lose, so a fixed intake stops working long before the straight line says.
Basal rate — kcal, multiplied by — for —. That is what you burn on an average day at your current weight — not a target, just the line you are eating above or below.
Twenty-six weeks, if you eat this every day
Week by week, with the arithmetic left in
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How long until half the gap is gone
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Three formulas, one dinner
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Katch-McArdle, the fourth formula people reach for, is missing on purpose: it needs your lean body mass, and this page never asked for it. Handing it a guessed body-fat percentage would make it the least trustworthy row here, not the most.
Where each number comes from
- Basal rate is Mifflin-St Jeor: 10 × kg + 6.25 × cm − 5 × years, then +5 for men and −161 for women. The four terms are listed above so you can add them up yourself.
- The multiplier is a base for the rest of your day — 1.15 desk, 1.30 on your feet, 1.45 physical work — plus 0.05 for each training day. Four sessions at a desk job gives 1.35. These are conventional bands, not measurements of you.
- The target is maintenance −20% to lose, +12% to gain, or maintenance itself to hold.
- Protein is 2.2 g per kg when losing and 1.8 g when gaining or holding, then capped at 40% of the day's calories — without that cap a heavy person in a deficit gets handed a negative carb number.
- 7,700 kcal per kg is the conventional figure for body fat (3,500 per pound). It is a rule of thumb, not a constant: early weeks move faster because of water, and not all of a deficit comes out of fat.
- The solid line recomputes basal rate from your new weight each week and feeds it back in. The dashed line does not — it just repeats week one forever. That is the only difference between them, and it is why they separate.
- The settling point is where the two sides meet: the weight at which maintenance equals the intake you are holding. Solve (10 kg + 6.25 cm − 5 age + s) × multiplier = intake for kg. At a steep deficit that answer often lands far below any sane weight — the arithmetic keeps going where the formula stopped meaning anything. It is there to show you the deficit closes itself, not to give you a target.
- The six-row table recomputes maintenance from the weight printed on that same row, not from a full-precision figure kept behind the scenes. Type the numbers in as they appear and they will agree.
- The weekly decay factor is 1 − multiplier ÷ 110. That 110 is 7,700 kcal per kg divided by 70 — ten kcal of basal rate per kilo, seven days a week. It is why the pace a gap closes at carries no information about you beyond your multiplier.
- The two older formulas are quoted with their published constants: Harris-Benedict as printed in 1919, and the Roza and Shizgal revision of 1984. Both are then run on the same intake and the same multiplier as the row above them, so the only thing being compared is the basal rate itself.
- Nothing here is measured. No body-fat percentage, no metabolic testing, no record of what you actually ate. Two people with identical inputs can differ by several hundred kcal a day, and none of this accounts for the slowdown that comes from dieting itself. Treat every number as a starting estimate to correct against the scale, redo it every few kilos, and take medical questions — including whether a deficit is a good idea for you at all — to someone who can examine you.
This is general information, not medical or dietary advice. Every figure on this page comes from a population formula, and conditions such as thyroid disease, diabetes, kidney or liver disease, eating disorders, pregnancy and a long list of medications change what is appropriate. If any of those apply, the numbers that count are the ones your doctor gives you.