Turning your measurements into a daily calorie target
1. Enter age, sex, height and weight
These four go into the Mifflin-St Jeor equation, which is the one most dietetic practice uses to estimate resting metabolism. Metric or imperial, whichever you think in. Weigh yourself at a consistent time — morning, before eating, is the usual advice — because a kilogram of overnight variation is enough to shift the target by twenty calories and mean nothing.
2. Pick the activity level your week actually looks like
This is the largest source of error on the page, and almost everyone rounds up. The multiplier applies to your entire resting rate, so one step too high can add three or four hundred calories a day. Three gym sessions on top of a desk job and a car commute is lightly active for most people. When in doubt, take the lower level and let a fortnight of real weights correct you.
3. Choose what you are trying to do
Maintain, lose or gain. The goal now changes the macronutrient split as well as the calorie figure — which sounds obvious, and was not true of the previous version, where protein was fixed regardless of what you selected.
4. Add your body fat percentage if you have one
Optional. It lets the protein figure be calculated from lean mass rather than total body weight, which matters a great deal at higher body-fat percentages. A reasonable estimate from our body fat calculator is enough; a guess is not, and no figure at all is better than a bad one.
5. Read the three targets together
Maintenance, loss and gain are shown side by side rather than one at a time, because the gaps between them are the useful information. Seeing that your loss target is only three hundred calories below maintenance tends to be more instructive than the single number you came for.
6. Check whether a floor has been applied
If the arithmetic produced a target below the level at which dieting without medical supervision stops being safe, the tool holds it at the floor and tells you so in plain language. It does not quietly print the low number, and it does not quietly print the high one either without saying why.
The equation behind the number, and its honest margin
The estimate starts with Mifflin-St Jeor, published in the American Journal of Clinical Nutrition in February 1990 and derived from 498 healthy adults aged 19 to 78, spanning both normal-weight and obese participants. For men it is 10 × weight in kg + 6.25 × height in cm − 5 × age + 5; for women the same, ending − 161.
That gives resting metabolic rate. Multiplying by an activity factor gives total daily energy expenditure, which is the figure a calorie target is built from:
- Sedentary (×1.2) — desk work, little deliberate exercise
- Lightly active (×1.375) — light exercise one to three days a week
- Moderately active (×1.55) — moderate exercise three to five days a week
- Very active (×1.725) — hard exercise six or seven days a week
- Extra active (×1.9) — hard daily training, or heavy physical work as well
Both halves carry error. A good prediction equation lands within roughly ten per cent of measured resting metabolism for most healthy adults, and the activity multiplier then amplifies whatever error you started with. Treat the number as a starting hypothesis, not a prescription: eat at it for two or three weeks, weigh yourself consistently, and adjust from what your body actually did. Your own two-week trend is better evidence than any equation on any website.
Why some targets stop at a floor and say so
The previous version calculated a weight-loss target as fifteen per cent below maintenance, with nothing underneath it. Applied to a 55-year-old woman of 45 kg at a sedentary activity level, that arithmetic produced 971 calories a day — below the level at which dieting without clinical supervision is considered safe, and below what her body needs simply to run its organs.
Very low calorie diets exist and have legitimate clinical uses. They are conducted with medical supervision and monitoring because at those intakes the documented risks include loss of muscle and bone, gallstones, electrolyte disturbance, cardiac arrhythmia and nutritional deficiency. A web page is not a supervising clinician, and a calculator that prints such a number without comment is not being helpful.
Targets are now held at a floor — commonly cited as around 1,200 calories a day for women and 1,500 for men when dieting unsupervised — and when the floor has been applied, the page says so and explains why rather than presenting the higher figure as though the arithmetic had simply come out that way.
Two tools on one site should not disagree about what a deficit is
This calculator used a flat fifteen per cent reduction. Our BMR and TDEE calculator used fixed steps of 250 and 500 calories. For a 70 kg man at moderate activity those are not the same thing: fifteen per cent is a 383-calorie deficit, sitting between the two fixed steps and matching neither.
Neither approach is wrong. A percentage scales with body size, which is sensible for very large or very small people; a fixed step is easier to plan meals around and is how most clinical advice is phrased. What is not defensible is two calculators on the same site handing the same visitor different answers without explanation. Both are now shown here, and the reason they differ is stated rather than hidden.
The rate of loss you should actually expect
The familiar rule — a 500-calorie daily deficit produces about half a kilogram of loss per week — comes from a 1958 paper by Max Wishnofsky, which put the energy content of a pound of body fat at roughly 3,500 calories.
It holds reasonably well for the first several weeks and increasingly overstates loss after that, for a simple reason: a smaller body burns less. As weight falls, resting metabolism falls with it, total expenditure falls too, and the deficit you started with quietly shrinks. Applied as a straight line, the rule predicts roughly 23 kg of loss in a year from a sustained 500-calorie deficit. Real outcomes are consistently well below that, and the shortfall is physiology rather than a failure of discipline.
Plan for the slowdown instead of treating it as failure. A loss of 0.5 to 1 per cent of body weight per week is the range usually described as sustainable; faster than that and an increasing share of what you lose is lean tissue rather than fat.
Macronutrients, and the setting that used to do nothing
The macro split now changes with your goal. In the previous build it did not, in a way worth describing plainly: the source contained an object mapping each goal to a protein share — 40 per cent for weight loss, annotated “higher protein for satiety”, 30 per cent for maintenance, 35 per cent for muscle gain — and the code read only the carbohydrate and fat values from it. Protein came from an activity multiplier instead and did not vary by goal at all. Anyone reading the page source would have seen a description of behaviour the tool did not have, and a deficit is precisely the situation where protein matters most.
The ranges used here are the Acceptable Macronutrient Distribution Ranges published by the Institute of Medicine, now part of the National Academies of Sciences, Engineering, and Medicine, in the 2005 Dietary Reference Intakes report on energy and macronutrients: carbohydrate 45 to 65 per cent of energy, fat 20 to 35 per cent, and protein 10 to 35 per cent. Any split the tool produces stays inside those bounds.
For protein specifically, the International Society of Sports Nutrition’s 2017 position stand supports roughly 1.4 to 2.0 g per kilogram of body weight per day for building and maintaining muscle in physically active people, with the upper part of that range appropriate during energy restriction to protect lean tissue. Sedentary adults need considerably less — the general population reference is around 0.8 g per kilogram. Where you have entered a body fat percentage, the figure is calculated from lean mass, which avoids inflating the target for someone carrying substantial fat.
What a calorie target cannot account for
Food labels are approximate. Permitted tolerances on declared energy content are wider than most people assume, and portion estimation at home adds more. Ten to twenty per cent of unavoidable slack between what you record and what you ate is normal.
Absorption is not total. You do not extract every calorie from everything. Whole nuts, high-fibre foods and heavily processed versus minimally processed forms of the same ingredient differ measurably in what actually reaches you.
Non-exercise movement varies enormously. The energy spent fidgeting, standing, pacing and generally not sitting still differs by hundreds of calories a day between people of identical size, and it tends to fall quietly when you eat less — one of the main reasons predicted and actual loss diverge.
Medication and medical conditions matter. Thyroid disorders, PCOS, some antidepressants and antipsychotics, corticosteroids and several other common treatments affect weight and energy balance in ways no equation can model.
When this page is the wrong place to get a number
Nothing here is medical advice, a diagnosis or a prescribed diet. It is arithmetic on published equations, with its sources named.
Please take your targets from a doctor or registered dietitian rather than this page if you are pregnant or breastfeeding, under 18, managing diabetes or kidney disease, recovering from surgery or serious illness, or living with any history of an eating disorder. If you are aiming to lose a substantial amount of weight, or your weight has changed noticeably without your changing anything, that is a conversation to have with a clinician rather than a calculator.
Nothing you enter is sent anywhere
Every calculation runs in your browser. Age, sex, height, weight, activity level, goal and body fat percentage are never transmitted, stored or logged, and there is no account and no upload. The page keeps working with the connection off once loaded. There is also no artificial delay: the previous build ran a 1.5-second spinner over arithmetic that completes in microseconds, and it is gone.
Questions people ask about daily calories
How many calories should I eat to lose weight?
Roughly 250 to 500 below your maintenance figure for most people, subject to the safety floor. Larger deficits do not reliably produce proportionally faster fat loss and do reliably cost more lean tissue.
Why is my target different from another calculator?
Usually the activity multiplier, occasionally the equation. A tool using the older Harris-Benedict equation typically reads a little higher than Mifflin-St Jeor. Differences of a hundred calories or so are ordinary; a difference of five hundred usually means the two of you selected different activity levels.
Can I eat below the floor if I really want to lose weight faster?
Not without supervision, and this page will not help you do it. Below roughly 1,200 calories for women and 1,500 for men, the documented risks are real enough that clinical programmes doing this monitor patients. If you need faster loss for a medical reason, that is a reason to see a doctor.
Do I need to count macros as well as calories?
Calories determine whether weight moves; protein largely determines how much of the change is muscle rather than fat. If you track one extra thing, make it protein. Carbohydrate and fat can sit anywhere inside the published ranges according to what you actually enjoy eating.
Should I eat back the calories my fitness tracker says I burned?
Rarely, and not in full. Trackers and calculators generally report gross energy cost, which includes what you would have burned at rest during that time anyway. Our calories burned calculator shows the net figure first for exactly this reason.
Why did my weight loss stop even though I did not change anything?
Because your maintenance figure fell as you did. A smaller body burns less, and non-exercise movement tends to drop during a deficit. Recalculate at your current weight every four to six kilograms.
Is a 1,200-calorie diet safe?
It is the conventional floor for unsupervised dieting in women rather than a recommendation, and it is genuinely hard to meet micronutrient needs there. Most people do better with a smaller deficit they can sustain for months than a large one they abandon in three weeks.
Does the goal setting really change the macros now?
Yes. Protein rises for weight loss and for muscle gain and sits lower for maintenance, within the published ranges. In the previous build the setting existed and changed nothing about protein at all.
Do you store my details?
No. Nothing is saved or transmitted.
Sources behind these numbers
- Mifflin MD, St Jeor ST et al, “A new predictive equation for resting energy expenditure in healthy individuals”, American Journal of Clinical Nutrition, February 1990 (PMID 2305711).
- Institute of Medicine / NASEM — Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids, 2005, for the Acceptable Macronutrient Distribution Ranges.
- Jager R et al, “International Society of Sports Nutrition Position Stand: protein and exercise”, 2017, for the 1.4 to 2.0 g/kg range.
- Wishnofsky M, 1958 — the origin of the 3,500-calorie-per-pound rule, and the reason it overstates loss over time.
- NHS — healthy weight, for safe rates of change.
- CDC — about healthy weight and growth.
Tools people open next to this one
- Calories Burned Calculator — net and gross figures for specific activities.
- Body Fat Calculator — supplies the lean-mass figure the protein target prefers.
- Water Intake Calculator — the other daily figure worth getting right.
