Calorie Calculator

Most adults need somewhere between 1,600 and 3,000 calories a day to maintain their weight. The exact number depends on your size, age, gender, and how active you are. This calculator estimates that figure - your Total Daily Energy Expenditure (TDEE) - by first working out the calories your body burns at rest and then scaling that up for your activity level. Eat close to your TDEE and your weight stays roughly stable; eat consistently below it and you lose weight; eat above it and you gain.

Your daily calorie burn is built from three layers. The largest is your Basal Metabolic Rate (BMR) - the energy your body uses just to keep you alive at complete rest: breathing, circulating blood, maintaining body temperature, and repairing cells. For most people BMR is 60-70% of the calories they burn in a day. If you only want that resting number, the BMR Calculator reports it on its own.

On top of BMR sits the thermic effect of food - the roughly 10% of your intake spent digesting, absorbing, and storing what you eat - and physical activity, which covers both deliberate exercise and everyday movement like walking, fidgeting, standing, and housework (often called NEAT, non-exercise activity thermogenesis). NEAT is the most variable part of the equation and is a big reason two similar people can have very different calorie needs. This calculator folds the thermic effect and all activity into a single activity multiplier applied to your BMR:

To see how much the activity level alone matters: a 70 kg, 175 cm, 25-year-old man has a BMR of about 1,674 calories. At “moderately active” his maintenance calories work out near 2,594 a day (the full step-by-step is in the worked example below), but change nothing except the activity level and the number moves by hundreds: at sedentary he would be near 2,009, at extra active near 3,180.

That sensitivity is why the activity multiplier is the input people most often get wrong - most people overestimate how active they are, and a desk job counts as sedentary even if you train a few times a week.

Beyond activity level, several factors move your calorie needs up or down:

• Body size and composition. A larger body burns more at rest, and muscle burns more than the same weight of fat. This is the main reason men usually need more calories than women of the same weight - on average they carry more lean mass.
• Age. Resting metabolism declines gradually from your twenties onward, partly from muscle loss and partly from changes in the tissue itself, so calorie needs fall by roughly 1-2% per decade even if your weight is stable.
• Recent dieting. A long or aggressive diet lowers your calorie burn by more than the weight loss alone would predict - a response called adaptive thermogenesis - and it can take weeks of eating at maintenance for that to recover.
• Hormones and health conditions. Thyroid function, some medications, pregnancy, breastfeeding, and illness all shift calorie needs, sometimes substantially.
• Environment. Sustained cold or heat, and life at high altitude, each raise energy expenditure modestly.

The calculator cannot see most of these, which is why its output is a starting estimate rather than a prescription. Your own results over a few weeks are the real measurement.

There is no single “true” calorie equation - every one is a population average fitted to a research sample, and your real metabolism can sit 5-10% either side of the prediction. Three equations are in common use:

This calculator uses Mifflin-St Jeor because it is the best-validated choice when all you have is height, weight, age, and gender. Katch-McArdle can be more accurate for a lean, muscular person, but only with a trustworthy body fat figure - if you want to explore that route, estimate yours with the Body Fat Calculator first. Whichever equation you use, treat the result as a well-informed starting point, then adjust based on what the scale actually does over two to four weeks.

1. Find your TDEE. Enter your details in the calculator above and note the maintenance number. This is what you burn on an average day at your current activity level.
2. Set a goal and a target intake. To lose weight, subtract 250-500 calories. To gain, add 250-500. Either change produces roughly half a pound to a pound of weight change per week.
3. Track what you eat for one to two weeks. Use a food scale and a logging app, and weigh food raw where you can. Studies consistently find people underestimate their intake by 20-40% from memory, so measuring is the entire point of the exercise.
4. Weigh yourself consistently. Same time of day, same conditions, several times a week, and compare weekly averages rather than single readings - daily swings of 1-2 kg from water, sodium, and digestion are normal and mean nothing on their own.
5. Adjust after two to four weeks. If your weekly average is not moving the way you want, change intake by about 100-200 calories and wait another two to four weeks. Your TDEE also falls as you lose weight, so plan to recalculate every 4-5 kg (10 lb) of change.

Calorie counting is a measurement tool, not a permanent lifestyle for most people. Many use it for a focused block of a few months to learn what portions and foods fit their needs, then move to a lighter approach - portion habits, hunger cues, a weekly weigh-in - once those lessons stick.

A sustained daily deficit translates into a predictable weekly loss:

The 3,500-calorie rule is a simplification. Some early loss is water and glycogen, some later loss is lean tissue, and your body partly offsets a deficit by burning less, so real-world results usually run a little slower than the arithmetic. A deficit at the smaller end of the range, protected by adequate protein and some resistance training, keeps more of your weight loss coming from fat.

Gaining works the same way in reverse, but a surplus only builds muscle if it is paired with progressive resistance training and enough protein - otherwise most of a large surplus is stored as fat. A modest surplus of 250-350 calories is enough for most people who are training to add muscle.

Yes - energy balance is the mechanism behind all weight change, and no diet escapes it. What makes it feel unreliable in practice is that both sides of the equation move. When you eat less, your body can lower the “out” side by making you subtly less active, reducing NEAT, and trimming the cost of movement, so a plan that worked for a month can stall even though nothing obvious changed.

The answer is not to abandon the calorie framework but to expect the adjustments: take a break at maintenance for a week or two when progress stalls, keep protein high, keep training, and re-measure your TDEE as your weight comes down. Food quality still matters enormously for hunger, energy, and health - it just is not a separate mechanism from calories.

Zigzag cycling means varying your intake day to day while keeping the same weekly average, instead of eating an identical number every day. A common pattern is a slightly larger deficit on rest days and a smaller one (or maintenance) on hard training days, with daily figures spread roughly 200-300 calories either side of the average.

The practical case for it is flexibility rather than a metabolic trick: it lets you eat more around social events or heavy workouts without breaking the week’s numbers, which improves adherence. Evidence that it meaningfully outpaces steady dieting for fat loss is limited, so treat it as an adherence tool - useful if a rigid daily target frustrates you, unnecessary if it does not.

Any calorie calculator has built-in limits worth knowing:

• It uses total body weight, not body composition. Two people of the same weight, height, age, and gender get the same estimate here even if one is far more muscular. If body composition matters for you, the Body Fat Calculator and a Katch-McArdle estimate may suit you better.
• The activity multiplier is a broad bracket. Two “moderately active” people can genuinely differ by several hundred calories a day depending on their job, step count, and how hard their workouts really are.
• Individual metabolism varies by 5-10% around the prediction for reasons including genetics, hormones, past dieting, and medical conditions.
• Your TDEE is not fixed. It drops as you lose weight and as you age, and it adapts downward during a prolonged deficit - which is why periodic recalculation beats setting a number once.

Use the calculator’s number to choose a sensible starting intake, then let two to four weeks of consistent tracking tell you what your body is actually doing. Calorie needs are one piece of a bigger picture - see also the BMI Calculator for where your weight sits relative to height, and the Ideal Weight Calculator for a clinically-derived target-weight range.