Calorie Calculator

How to use this calculator#

1. 1
   Fill in sex, age, height and current weightThese four feed the Mifflin-St Jeor equation that produces your basal metabolic rate. Use today's weight — a goal weight produces the calorie needs of a body you do not have yet.
2. 2
   Pick the activity level that matches a typical week, not your best weekThe multiplier is meant to cover your whole week including work, commuting and chores. A desk job plus three or four gym sessions is 'moderately active' (1.55). 'Very active' (1.725) means manual work or a heavy training block, and almost nobody with an office job belongs at 1.9.
3. 3
   Read maintenance firstMaintenance is the anchor for everything else. Note it, eat at it for two to three weeks if you can, and check whether your weight actually holds steady before you subtract anything.
4. 4
   Choose a rate of change you can hold for monthsA 550 kcal daily deficit is about 0.5 kg a week and suits most people. A 1,100 kcal deficit is only realistic for those carrying substantial excess weight, and ideally with clinical oversight. On the gaining side, 300–550 kcal above maintenance alongside resistance training adds muscle without excessive fat.
5. 5
   Weigh the trend, not the dayGlycogen, salt and fluid can move the scale a kilogram overnight. Weigh at the same time under the same conditions and judge the seven-day average after two or three weeks, then adjust the target by 100–200 kcal if the trend is off.

The formula#

How your daily calorie target is built#

The calculation runs in two steps. First it estimates basal metabolic rate with the Mifflin-St Jeor equation, then it multiplies that by an activity factor: 1.2 for sedentary, 1.375 for light exercise one to three days a week, 1.55 for moderate, 1.725 for very active and 1.9 for a physical job or two training sessions a day.

A 35-year-old woman at 165 cm and 65 kg has a BMR near 1350 kcal. At the moderate factor of 1.55 her maintenance sits around 2085 kcal per day. Eating roughly 550 kcal below that points to about half a kilogram of loss per week, since a kilogram of body fat stores close to 7700 kcal.

Choosing a sensible rate of change#

Faster is not better. Deficits beyond about 1000 kcal a day make it hard to hit protein and micronutrient targets and increase the share of weight lost as muscle rather than fat. Half a kilogram per week suits most people; a full kilogram per week is realistic only for those carrying substantial excess weight, and ideally with professional oversight.

On the gaining side, a surplus of 300-500 kcal is usually enough to support muscle growth alongside resistance training. Much larger surpluses mostly add fat. Whichever direction you go, hold the number steady for two to three weeks before judging it, because water weight, glycogen and salt intake can swing the scale by a kilogram or more day to day.

What this number cannot tell you#

Calorie estimates say nothing about food quality, fibre, protein adequacy or micronutrients, and they do not account for medical conditions, medications, pregnancy or breastfeeding, all of which change energy needs substantially. These figures are general information, not medical or dietary advice, and they are not appropriate for children.

If you have diabetes, kidney disease, a history of disordered eating, or you are pregnant, set targets with a doctor or registered dietitian rather than a web tool. Anyone losing weight without trying should be checked by a clinician instead of adjusting their intake.

Worked examples#

Reference tables#

Common mistakes#

• Counting exercise twiceIf you selected 'moderately active' because you train four times a week, those sessions are already inside the multiplier. Adding a fitness tracker's exercise calories on top typically double-counts 300–500 kcal a day and quietly erases the deficit.
• Trusting tracker and machine calorie readoutsWrist-worn devices and cardio machines commonly overstate energy burned by 20–90% depending on the activity, because they infer expenditure from heart rate and motion rather than measuring it. Use them for consistency between sessions, not as an intake budget.
• Underreporting what you eatDoubly-labelled-water studies have repeatedly found that people underreport intake substantially, most often by leaving out cooking oil, drinks and portions eaten standing up. If the scale is not moving on a supposed 500 kcal deficit, measurement is the first thing to check, not metabolism.
• Never recalculating after weight changesA 10 kg loss lowers the Mifflin-St Jeor BMR by 100 kcal a day, and about 155 kcal of maintenance at a 1.55 multiplier. Recalculate every 5 kg or so, otherwise the plateau is arithmetic rather than a metabolic problem.

Frequently asked questions#

Key terms#

Maintenance calories

The intake at which body weight holds steady over weeks. Numerically the same as TDEE, and the reference point every loss or gain target is measured from.

Calorie deficit

Eating below maintenance so the body draws on stored energy. Roughly 7,700 kcal of cumulative deficit corresponds to a kilogram of body fat, though the relationship flattens over time.

Activity factor

The multiplier applied to BMR to account for digestion, daily movement and exercise. Ranges from 1.2 for sedentary to 1.9 for physically demanding work or twice-daily training.

NEAT (non-exercise activity thermogenesis)

Energy burned through everything that is not deliberate exercise — walking, standing, fidgeting, housework. It varies hugely between people and is the main reason two people at the same weight and training load need different intakes.

Adaptive thermogenesis

The fall in energy expenditure beyond what weight loss alone predicts, seen during and after sustained dieting. It is one reason deficits stop producing the expected loss and targets need revisiting.

Energy balance

The relationship between energy consumed and energy expended. Weight change over time follows the balance, which is why total calories — not the macronutrient split — drive the direction of travel.

Sources#