Calorie Calculator
Estimate how many calories you burn each day (your TDEE) and how many to eat to lose, maintain or gain weight — based on your age, sex, height, weight and activity level.
Understanding your daily calorie needs
A calorie is simply a unit of energy. Every day your body spends energy keeping you alive — beating your heart, breathing, repairing tissue — and then more on top of that to move, work and exercise. The total amount of energy you burn in 24 hours is your total daily energy expenditure (TDEE), and it is the single most useful number for managing your weight. Eat roughly your TDEE and your weight tends to hold steady; eat consistently less and you lose weight; eat consistently more and you gain. This calculator estimates that target number from your age, sex, height, weight and how active you are.
Because energy needs differ enormously from one person to the next, there is no universal "right" number of calories. A tall, muscular, active person can need more than double the calories of a smaller, sedentary one. That is why a personalised estimate beats a generic figure like "2,000 calories a day," which is only an average label used on food packaging.
How to use this calculator
Enter your age, sex, height and weight, then choose the activity level that honestly reflects a typical week — including job activity, not just gym sessions. Most people overestimate this, so when in doubt pick the lower option. The calculator returns your maintenance calories (your TDEE) plus suggested targets for losing, maintaining or gaining weight. Use the maintenance number as your baseline, follow it for two to four weeks while tracking your weight, then nudge intake up or down based on what the scale actually does.
How it's calculated
The estimate runs in two steps. First it calculates your basal metabolic rate (BMR) — the energy you would burn at complete rest — using the widely used Mifflin-St Jeor equation, which combines your weight, height, age and sex. Second, it multiplies that BMR by an activity multiplier to account for everything you do beyond resting. BMR × activity multiplier = TDEE. The multipliers range from about 1.2 for a sedentary lifestyle up to roughly 1.9 for very heavy daily training or physical labour.
To change your weight, you adjust intake relative to TDEE. A common rule of thumb is that about 3,500 calories roughly corresponds to one pound (around 0.45 kg) of body fat, so a daily deficit of ~500 calories points toward losing about a pound a week. Treat this as a rough guide rather than a precise law — real bodies adapt, water weight fluctuates, and the figure varies between people. For gaining, a modest surplus of ~250–500 calories a day supports lean gain while limiting excess fat.
Worked example
Imagine a 35-year-old woman, 165 cm tall, weighing 68 kg, who is lightly active. Her Mifflin-St Jeor BMR works out to roughly 1,400 calories. Multiplying by a "lightly active" factor of about 1.375 gives a TDEE near 1,925 calories — her rough maintenance level. To lose about half a kilogram a week she might aim for around 1,425 calories (a ~500-calorie deficit), while to gain slowly she might eat around 2,175.
| Activity level | Typical week | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise | 1.2 |
| Lightly active | Light exercise 1–3 days/week | 1.375 |
| Moderately active | Moderate exercise 3–5 days/week | 1.55 |
| Very active | Hard exercise 6–7 days/week | 1.725 |
| Extra active | Physical job or twice-daily training | 1.9 |
Limitations & tips
These figures are estimates, not measurements. They cannot capture your exact body composition, hormones, medications or day-to-day variation, and activity multipliers in particular are easy to overstate. Very aggressive "crash" deficits often backfire: they are hard to sustain, can sap energy and lift hunger, and may cost you muscle, which lowers your metabolism further. A slower, moderate deficit is usually more livable and easier to keep off. Finally, calorie quantity is only half the picture — the quality of those calories matters for satiety, nutrition and health, so build most of your intake from whole foods, adequate protein and fibre. These numbers are general information only and are not a substitute for advice from a doctor or registered dietitian, especially if you have a medical condition or eating-disorder history.
Frequently asked questions
How are my calorie needs calculated?
We estimate your basal metabolic rate (BMR) with the Mifflin-St Jeor equation, then multiply by an activity factor from 1.2 (sedentary) to 1.9 (very active) to get your total daily energy expenditure (TDEE).
How many calories should I eat to lose weight?
A deficit of about 500 calories a day tends to lose roughly 0.5 kg (1 lb) per week. The table shows several goals; very low intakes are floored at a safe minimum to discourage unsafe dieting.
Are these numbers exact?
No — they're estimates. Actual needs vary between people and from day to day. Track your weight over two to four weeks and adjust your intake from the maintenance figure if the scale isn't moving the way you want.
What's the lowest number of calories I should eat?
Going very low for long stretches is risky and hard to sustain. As a rough floor, many guidelines suggest not dropping below about 1,200 calories a day for women or 1,500 for men without professional supervision. A moderate deficit you can stick to beats an extreme one you abandon.
Why does weight loss slow down even when I keep eating the same?
As you lose weight you become lighter, so you burn fewer calories doing the same activities, and your body adapts somewhat to lower intake. This is normal. You may need to recalculate your TDEE at your new weight and gently adjust your target to keep progress moving.
Do the type of calories matter, or just the total?
For weight change, total calories drive the result, but quality still matters a lot. Protein and fibre-rich whole foods keep you fuller and protect muscle and overall nutrition, making the same calorie target far easier to live with than the same number from sugary, processed foods.
Sources & references
- Mifflin MD, et al. — "A new predictive equation for resting energy expenditure in healthy individuals," Am J Clin Nutr (1990) — the equation this calculator uses to estimate BMR before applying the activity multiplier.
- "Dietary Guidelines for Americans, 2020–2025" (PMC, National Institutes of Health) — the federal guidance on calorie needs and healthy eating patterns this tool's targets align with.
- NIH (NIDDK) — Body Weight Planner — a research-based calorie and weight-change estimation tool from the National Institutes of Health.
Last updated: July 2026 · How we calculate
BriskToolbox provides estimates for general information only and is not medical advice. Talk to a healthcare professional about your individual health.