Calories and Macros: The Numbers That Actually Matter
How BMR, TDEE and macro splits fit together, and what the formulas can and cannot tell you.
Calorie targets look precise and are not. Every equation in this area is a population estimate with meaningful error for any individual, which is why the number you calculate should be treated as a starting point to adjust, not a prescription.
Where your energy actually goes
| Component | Share of daily burn | Notes |
|---|---|---|
| Basal metabolic rate | 60–70% | Keeping you alive at rest |
| Thermic effect of food | ~10% | Highest for protein, lowest for fat |
| Non-exercise activity | 15–30% | Walking, fidgeting, standing — highly variable |
| Deliberate exercise | 5–15% | Usually smaller than people assume |
The largest controllable variable for most people is non-exercise activity, not the gym session. It also falls automatically during a prolonged deficit, which is a major reason weight loss stalls.
Estimating the number
The Mifflin-St Jeor equation is the current default for resting metabolic rate:
men: BMR = 10×kg + 6.25×cm − 5×age + 5
women: BMR = 10×kg + 6.25×cm − 5×age − 161
TDEE = BMR × activity factor (1.2 sedentary → 1.9 very active)Splitting the macros
Protein first, because it preserves muscle in a deficit and is the most satiating per calorie. Fat has a floor for hormone production. Carbohydrate takes whatever remains and fuels training intensity.
| Macro | Per gram | Practical target |
|---|---|---|
| Protein | 4 kcal | 1.6–2.2 g per kg body weight |
| Fat | 9 kcal | 0.6–1.0 g per kg, minimum ~20% of calories |
| Carbohydrate | 4 kcal | The remainder |
| Alcohol | 7 kcal | No nutritional requirement |
Setting a rate of change
A deficit of about 500 kcal a day corresponds to roughly 0.45 kg a week, but the body adapts: metabolic rate falls slightly, movement decreases and water shifts mask fat loss for weeks at a time. Aim for 0.5–1% of body weight per week and judge progress on a fortnightly trend, not a daily reading.
- Weigh at the same time of day under the same conditions.
- Use a weekly average; day-to-day swings are mostly water and gut contents.
- Expect plateaus of two to three weeks and only adjust intake after one persists.
- Take a diet break at maintenance every 8–12 weeks on a long cut.
Start with the calorie calculator and macro calculator, then check protein against body weight with the protein intake calculator.
Frequently asked questions
Do I need to hit my macros exactly?
No. Within roughly 10 g of protein and fat and 20 g of carbohydrate is close enough. Consistency across a week matters far more than precision on any single day.
Are calories from different foods equivalent?
Energetically yes, practically no. Protein costs more to digest, and whole foods are more satiating per calorie, so the same total is far easier to sustain with better food choices.
Why has my weight loss stalled at the same intake?
A smaller body burns less, non-exercise movement declines, and portion accuracy drifts over time. Re-run the calculation at your current weight and re-weigh food for a week before cutting further.
Is a low-carb or low-fat diet better?
Controlled trials matching calories and protein show little difference in fat loss. Choose whichever you can sustain, and keep fat above the hormonal floor.