What is a calorie calculator?
The Calorie Calculator estimates the number of calories a person needs to consume each day to maintain their body weight, based on age, gender, height, weight and activity level. It can also give simple guidelines for gaining or losing weight — for example, subtracting about 500 calories a day from your maintenance figure is a common starting point for weight loss. You can switch between Metric (kg, cm) and US Units (ft + in, lb) tabs; the result is identical either way.
How the calculation works
Your daily needs are built from two pieces. First, your Basal Metabolic Rate (BMR) — the energy your body burns at complete rest just to keep you alive: breathing, heartbeat, brain activity, body temperature. Second, an activity factor that multiplies BMR to account for everything else you do during the day, from walking to the kitchen to training for a marathon. The result, BMR × activity factor, is called your Total Daily Energy Expenditure (TDEE):
TDEE = BMR × activity factor (1.2 – 1.95)
The formulas used
The Harris-Benedict Equation was one of the earliest formulas for BMR. It was revised in 1984, and was the standard until the Mifflin-St Jeor Equation arrived in 1990, which is now considered the most accurate for most people. The Katch-McArdle formula is different: it uses lean body mass, so it can be more accurate for people who are leaner and know their body fat percentage.
Mifflin-St Jeor:
Men: BMR = 10W + 6.25H − 5A + 5 Women: BMR = 10W + 6.25H − 5A − 161
Revised Harris-Benedict:
Men: BMR = 13.397W + 4.799H − 5.677A + 88.362 Women: BMR = 9.247W + 3.098H − 4.330A + 447.593
Katch-McArdle:
BMR = 370 + 21.6 × (1 − F) × W
Where W is body weight in kg, H is height in cm, A is age, and F is body fat expressed as a decimal (for example 0.15 for 15% body fat).
Activity factors
| Level | Description | Factor |
|---|---|---|
| Sedentary | Little or no exercise | 1.2 |
| Light | Exercise 1–3 times/week | 1.375 |
| Moderate | Exercise 4–5 times/week | 1.55 |
| Active | Daily exercise, or intense exercise 3–4 times/week | 1.725 |
| Very Active | Intense exercise 6–7 times/week | 1.9 |
| Extra Active | Very intense daily exercise, or a physical job | 1.95 |
How to use the result for weight loss or gain
One kilogram of body fat stores roughly 7,700 calories (about 3,500 calories per pound). If you eat 500 calories less than your maintenance needs every day, you create a weekly deficit of 3,500 calories — about 0.45 kg (1 lb) of weight loss per week. Cutting 1,000 calories a day roughly doubles that pace. The same logic in reverse applies to gaining weight.
It is generally inadvisable to lower calorie intake by more than about 1,000 calories per day. Losing more than 2 pounds a week often involves muscle loss, which lowers your BMR and makes the weight harder to keep off. Extreme restriction can also slow your metabolism and encourage the weight to return once you eat normally again. Harvard Health Publications suggests that women get at least 1,200 calories and men at least 1,500 calories a day unless under medical supervision.
Zigzag calorie cycling
Some people prefer zigzag calorie cycling: instead of eating the same number of calories every day, they alternate higher- and lower-calorie days that average out to the same weekly target. For example, a 2,000 kcal/day target is the same as eating 2,300 kcal on three days and 1,775 kcal on the other four. The idea is that the body does not adapt to a constant lower intake, and it makes social occasions easier to plan around. The gap between high and low days is usually kept to about 200–300 calories.
Energy from food components
| Component | Calories per gram | kJ per gram |
|---|---|---|
| Fat | 8.8 | 37 |
| Protein | 4.1 | 17 |
| Carbohydrates | 4.1 | 17 |
| Fiber | 1.9 | 8 |
| Ethanol (alcohol) | 6.9 | 29 |
| Organic acids | 3.1 | 13 |
| Polyols (sugar alcohols) | 2.4 | 10 |
Calories in common foods
| Food | Serving | Calories |
|---|---|---|
| Apple | 1 medium (4 oz) | 59 |
| Banana | 1 medium (6 oz) | 151 |
| Chicken breast, cooked | 2 oz | 136 |
| Egg | 1 large | 78 |
| Beef, regular, cooked | 2 oz | 142 |
| Rice, cooked | 1 cup | 206 |
| Bread, white | 1 slice (1 oz) | 75 |
| Butter | 1 tablespoon | 102 |
| Cheeseburger | 1 sandwich | 285 |
| Pizza | 1 slice (14 inch) | 285 |
| Dark chocolate | 1 oz | 155 |
| Beer | 1 can | 154 |
| Whole milk | 1 cup | 146 |
| Orange juice | 1 cup | 111 |
These are averages — exact values vary by brand and preparation. Remember that calories from drinks can make up around 20% of a typical person's intake, and much of that is "empty calories" from added sugar.
A worked example
A 30-year-old man who is 170 cm (5'7") tall and weighs 70 kg (154 lb), exercising 4–5 times a week, has a Mifflin-St Jeor BMR of 10×70 + 6.25×170 − 5×30 + 5 = 1,617.5 kcal. Multiplied by a moderate activity factor of 1.55, his maintenance need is about 2,507 kcal per day. Eating roughly 2,000 kcal a day should lose him close to 0.5 kg per week.
This calculator provides estimates for educational purposes and is not medical advice. Individual calorie needs vary with genetics, muscle mass, health conditions and medication. Consult a doctor or registered dietitian before starting any diet or exercise programme.