How daily calorie needs are calculated
Your total daily energy expenditure (TDEE) is what you burn in 24 hours. It starts with basal metabolic rate — the energy needed to keep you alive at rest, which is 60% to 70% of the total for most people — and multiplies it by an activity factor.
Three equations are in common use for the resting figure. Mifflin-St Jeor, the default here, has repeatedly proved the most accurate general-population predictor, typically within about 10% of measured values. The revised Harris-Benedict equation is older and tends to run slightly high. Katch-McArdle ignores sex and age and works from lean body mass instead, which makes it the better choice for very muscular people — provided you have a reasonable body fat estimate to feed it.
| Equation | Men | Women | Best suited to |
|---|---|---|---|
| Mifflin-St Jeor (1990) | 10W + 6.25H − 5A + 5 | 10W + 6.25H − 5A − 161 | Most adults; the recommended default |
| Revised Harris-Benedict (1984) | 88.362 + 13.397W + 4.799H − 5.677A | 447.593 + 9.247W + 3.098H − 4.330A | Comparison with older references |
| Katch-McArdle | 370 + 21.6 × lean mass | 370 + 21.6 × lean mass | Lean or muscular people with a known body fat % |
Activity levels and what they mean
The activity multiplier is the least precise part of the estimate, and the most common source of error is optimism. Most people who describe themselves as moderately active are lightly active by these definitions. If your weight has been stable, your true maintenance is whatever you are eating now — use that as the check on any formula.
| Level | Typical week | Multiplier |
|---|---|---|
| Sedentary | Desk work, little or no deliberate exercise | 1.20 |
| Light | Exercise 1–3 times a week | 1.375 |
| Moderate | Exercise 4–5 times a week | 1.465 |
| Active | Daily exercise, or intense exercise 3–4 times a week | 1.55 |
| Very active | Intense exercise 6–7 times a week | 1.725 |
| Extra active | Very intense exercise daily, or a physically demanding job | 1.90 |
The four components of energy expenditure
Total expenditure breaks down into four parts, which explains why activity multipliers are approximate.
- Basal metabolic rate: 60–70% of the total. Driven mostly by lean body mass, which is why larger and more muscular people burn more at rest.
- Thermic effect of food: roughly 10%. Digestion itself costs energy, and protein costs the most — 20–30% of its calories versus 5–10% for carbohydrate and fat.
- Exercise activity: highly variable. Deliberate training, from nothing to several hundred calories a day.
- Non-exercise activity (NEAT): fidgeting, walking, standing, and posture. This varies by up to 2,000 calories a day between individuals and tends to fall unconsciously when you diet, which is a major reason weight loss slows.
Calorie deficits and realistic rates of loss
A pound of body fat stores roughly 3,500 calories, so a 500-calorie daily deficit predicts about a pound a week. That arithmetic works reasonably well at first and then overstates results, because a smaller body burns fewer calories and NEAT declines. Expect the rate to slow and plan to recalculate every 10 to 15 pounds.
Sustainable targets are 0.5 to 1% of body weight per week. Aggressive deficits cost lean mass alongside fat, and intakes below roughly 1,200 calories for women or 1,500 for men make adequate nutrition difficult without medical supervision.
| Daily target | Breakfast | Lunch | Dinner | Snacks |
|---|---|---|---|---|
| 1,200 kcal | 300 | 350 | 400 | 150 |
| 1,500 kcal | 350 | 450 | 500 | 200 |
| 2,000 kcal | 500 | 600 | 650 | 250 |
Calories in common foods
Typical values for everyday foods, from USDA reference data. Portion size drives most of the variation — a large banana or a generous pour of oil can be half again what is listed — so treat these as anchors for estimation rather than exact counts.
| Food | Serving | kcal | kJ |
|---|---|---|---|
| Apple | 1 medium | 95 | 397 |
| Banana | 1 medium | 105 | 439 |
| Orange | 1 medium | 62 | 259 |
| Grapes | 1 cup | 104 | 435 |
| Strawberries | 1 cup | 49 | 205 |
| Carrot | 1 medium | 25 | 105 |
| Broccoli | 1 cup, chopped | 31 | 130 |
| Potato, baked | 1 medium | 161 | 674 |
| Egg | 1 large | 78 | 326 |
| Chicken breast, cooked | 3 oz (85 g) | 140 | 586 |
| Salmon, cooked | 3 oz (85 g) | 175 | 732 |
| Ground beef 85%, cooked | 3 oz (85 g) | 213 | 891 |
| White rice, cooked | 1 cup | 205 | 858 |
| Pasta, cooked | 1 cup | 220 | 920 |
| Bread | 1 slice | 80 | 335 |
| Whole milk | 1 cup (240 ml) | 149 | 623 |
| Cheddar cheese | 1 oz (28 g) | 114 | 477 |
| Almonds | 1 oz (28 g) | 164 | 686 |
| Peanut butter | 2 tbsp | 190 | 795 |
| Olive oil | 1 tbsp | 119 | 498 |
| Sugar | 1 tsp | 16 | 67 |
| Black coffee | 8 oz (240 ml) | 2 | 8 |
| Cola | 12 oz can | 140 | 586 |
| Beer | 12 oz (355 ml) | 153 | 640 |
| Wine | 5 oz (150 ml) | 125 | 523 |
Calories burned in common exercises
Energy burned depends on body weight as much as on the activity, which is why the same 30 minutes appears three times below. The figures are widely used estimates for 30 minutes of activity; individual differences in fitness, technique, and intensity move them by 20% or more in either direction.
| Activity | 125 lb (57 kg) | 155 lb (70 kg) | 185 lb (84 kg) |
|---|---|---|---|
| Walking, 3.5 mph | 107 | 133 | 159 |
| Running, 12 min/mile (5 mph) | 240 | 288 | 336 |
| Running, 10 min/mile (6 mph) | 295 | 360 | 420 |
| Cycling, 12–14 mph | 240 | 288 | 336 |
| Swimming, general | 180 | 216 | 252 |
| Hiking | 180 | 216 | 252 |
| Elliptical trainer | 270 | 324 | 378 |
| Basketball, game | 240 | 288 | 336 |
| Tennis | 210 | 252 | 294 |
| Weight lifting, general | 90 | 108 | 126 |
| Weight lifting, vigorous | 180 | 216 | 252 |
| Yoga | 120 | 144 | 168 |
| Golf, carrying clubs | 165 | 198 | 231 |
| Gardening | 135 | 162 | 189 |
Energy in food components
Food energy comes from four sources, and their densities are what make some foods so much more calorific than others by weight. Fat carries more than twice the energy of protein or carbohydrate per gram, which is why a tablespoon of oil outweighs a whole apple.
| Component | kcal per gram | kJ per gram |
|---|---|---|
| Carbohydrate | 4 | 17 |
| Protein | 4 | 17 |
| Fat | 9 | 37 |
| Alcohol | 7 | 29 |
| Dietary fibre | about 2 | about 8 |
Calories and kilojoules
A food calorie is really a kilocalorie — the energy to raise a kilogram of water by one degree Celsius — and much of the world labels food in kilojoules instead. One kilocalorie is 4.184 kilojoules, so a 2,000 kcal day is about 8,400 kJ. The calculator switches between the two; nothing else about the estimate changes.
Why the number on the label is not the whole story
Calorie counting is a useful estimate rather than a precise measurement. Food labels are permitted a margin of error around 20%, portion estimates drift, and absorption differs by food — whole nuts, for instance, yield fewer usable calories than their label implies because some fat is never absorbed.
Protein intake deserves separate attention when losing weight. Roughly 0.7 to 1 gram per pound of body weight helps preserve muscle in a deficit and increases satiety, which makes adherence easier. Two diets with identical calories can produce different body composition outcomes depending on protein and resistance training.