How Many Calories Do You Actually Need Each Day?

Your daily calorie target is not a fixed number you read off a chart. It depends on your body and how much you move. Here is how it is worked out.

Plantrino Guides · Updated 2026 · About a 9-minute read

"Eat 2,000 calories a day" is one of the most repeated pieces of nutrition advice in the world. It is also, for most people, wrong. That figure is a rough average printed on food labels for convenience. Your real number could be several hundred calories higher or lower. This guide explains where a personal calorie target comes from, so the figure you use is actually yours — and, since you are shopping in Australian supermarkets, how to translate it into the kilojoules printed on the back of the pack.

The Two Pieces of the Puzzle

Your daily calorie need is built from two parts: the energy your body uses just to stay alive, and the extra energy you burn through movement. Add them together and you get your total daily energy expenditure, often shortened to TDEE.

Nothing about this is mysterious. The first part is estimated from a short equation using your height, weight, age and sex. The second part is a multiplier that reflects how active your week genuinely is. The whole calculation takes about thirty seconds once you know the steps.

Step One: Basal Metabolic Rate

Your basal metabolic rate, or BMR, is the energy your body would burn if you spent the whole day lying still. It keeps your heart beating, your lungs working, and your temperature steady. For most people, BMR is the single biggest part of their calorie budget — often 60 to 70 percent of the total.

The most widely used and accurate way to estimate it is the Mifflin-St Jeor equation:

Let us work through an example. Take a 35-year-old woman who weighs 65 kilograms and is 165 centimetres tall:

• 10 × 65 = 650
• 6.25 × 165 = 1,031
• 5 × 35 = 175
• 650 + 1,031 − 175 − 161 = 1,345 calories

So her body burns roughly 1,345 calories per day at complete rest. But almost nobody spends the day at complete rest, which is where step two comes in.

Step Two: Activity Level

To turn BMR into a realistic daily figure, you multiply it by an activity factor. The factor reflects how much you move on a typical day, including exercise, work, and everyday tasks.

If our example woman is moderately active, her total daily need is 1,345 × 1.55 = 2,085 calories. If she were sedentary instead, it would drop to about 1,614. That gap of nearly 500 calories shows why a single "average" number serves almost nobody well.

Notice that the multiplier is doing a lot of work here. Getting your BMR slightly wrong shifts the answer by a few dozen calories; choosing the wrong activity factor shifts it by hundreds. Honesty about your week matters more than precision about your equation.

Calories or Kilojoules? Reading an Australian Label

Australia officially uses kilojoules, not calories. The nutrition information panel on every packaged food sold here leads with kilojoules, and the "average adult diet" reference used for percentage-daily-intake figures on those panels is 8,700 kJ. Overseas apps, recipe sites and fitness trackers usually speak in calories instead, so you will constantly be moving between the two units.

The conversion is straightforward arithmetic:

A quick sense-check: 8,700 kJ works out to roughly 2,079 calories, which is why the familiar "about 2,000 calories" figure and the Australian 8,700 kJ reference are really the same number wearing different clothes. And, like the calorie version, it is an average for labelling purposes rather than a target meant for you personally.

If you prefer rough mental maths at the shops, multiplying calories by four gets you close enough to compare two products on a shelf. Use the exact factor when you are setting an actual daily target.

Putting Real Numbers on It

Here is a second example worked all the way through, because the arithmetic is where the idea becomes useful. Take a 45-year-old man, 88 kilograms, 180 centimetres tall, who works a desk job in Brisbane and walks the dog most evenings plus one weekend bike ride. That is lightly active — factor 1.375.

• 10 × 88 = 880
• 6.25 × 180 = 1,125
• 5 × 45 = 225
• BMR = 880 + 1,125 − 225 + 5 = 1,785 calories
• TDEE = 1,785 × 1.375 = about 2,454 calories (roughly 10,270 kJ)

Suppose he wants to lose weight at a steady pace and settles on a 500-calorie daily deficit. His target becomes about 1,954 calories, or roughly 8,180 kJ. Over a week that is a 3,500-calorie deficit. Using the common rule of thumb that about 7,700 calories corresponds to roughly one kilogram of body weight, that points to about 0.45 kg a week — call it half a kilo, on a good week.

Now fast-forward six months. Say he is down to 80 kilograms. Recalculating with the same equation gives a BMR of 1,705 and a TDEE of about 2,344 — his maintenance level has dropped by around 110 calories a day simply because there is less of him to run. If he keeps eating 1,954, his deficit has quietly shrunk from 500 to about 390 a day. This is the single most common reason people say weight loss "stopped working". Nothing broke; the maths moved.

Using the Number for a Goal

Your TDEE is the amount of energy that keeps your weight stable. From there you can adjust:

• To lose weight, eat below your TDEE. A daily deficit of 300 to 500 calories is a steady, sustainable pace for most people.
• To maintain weight, eat close to your TDEE.
• To gain weight or build muscle, eat above your TDEE, typically by 250 to 500 calories paired with strength training.

A common rule of thumb is that a deficit of roughly 7,700 calories corresponds to about one kilogram of body weight. So a 500-calorie daily deficit points toward roughly half a kilogram of loss per week. Treat this as a guide rather than a guarantee — bodies adapt, and the maths is never perfectly tidy.

Whichever direction you are heading, pick the smallest adjustment that gets you there. A modest change you can keep up for six months will always beat an aggressive one you abandon in three weeks.

What the Number Does Not Tell You

A calorie target is a budget, not a meal plan. Two days that hit exactly the same number can feel completely different: one leaves you full and steady, the other leaves you raiding the pantry at nine at night. Protein and fibre tend to be the difference, and the Australian Dietary Guidelines are built around food groups rather than a single energy figure for exactly that reason.

The number also says nothing about how you feel, how you sleep, or how you perform. If hitting your target is making you exhausted, irritable or unable to train, the target is wrong for you regardless of what the equation said. Energy needs also shift with pregnancy, breastfeeding, illness, some medications and some medical conditions — situations where a general equation is not the right tool at all.

This guide is general information, not medical or nutritional advice. If you have a health condition, take regular medication, or want a plan built around your circumstances, talk to your GP or an Accredited Practising Dietitian.

Common Mistakes to Avoid

Overestimating activity

Many people pick a higher activity factor than their week really justifies. Three gym sessions surrounded by four sedentary days is "moderately active" at most. When in doubt, choose the lower factor and adjust upward later.

Cutting calories too hard

A very large deficit tends to backfire. It is difficult to sustain, it can cost you muscle, and hunger usually wins eventually. A modest deficit you can hold for months beats an extreme one you abandon in a week.

Forgetting that the number changes

As your weight changes, so does your BMR. If you lose ten kilograms, your calorie need falls, and a target that once created a deficit may now only maintain. Recalculate every so often.

Mixing up calories and kilojoules

Entering a kilojoule figure into a calorie field — or the reverse — produces an answer that is out by more than four times. It sounds too obvious to happen, but with an Australian label in one hand and an overseas app in the other, it happens constantly. Check which unit a tool is asking for before you type.

Trusting the "calories burned" figure on a watch

Wearable estimates of exercise energy are notoriously generous, and they overlap with the activity factor you already applied. Treat them as motivation, not as a licence to eat more.

Judging progress over days instead of weeks

Body weight swings with hydration, salt, and what is still working through your digestive system. A single morning on the scales tells you almost nothing. Compare weekly averages over two or three weeks before deciding your target needs changing.

Frequently Asked Questions

The honest answer to "how many calories do I need?" is: it depends, and the dependence is on facts you can measure. Estimate your BMR, multiply by an honest activity factor, convert to kilojoules if that is what your labels use, and you will have a personal number that beats any label average. From there, small consistent adjustments will always outperform dramatic ones.