Complete guide
Reviewed July 2026If calories decide whether you gain or lose weight, macros decide what that weight is made of and how you feel getting there. Two diets with identical calories can build muscle or lose it, leave you full or starving, and fuel your training or drain it - the difference is the split between protein, carbohydrate and fat. Tracking macros is how serious lifters, athletes and physique-focused dieters turn a calorie target into a body-composition result.
This calculator turns your daily calorie goal into gram targets for each macronutrient based on your objective. Below you'll find the calories-per-gram math, recommended splits for cutting, maintaining and bulking, protein guidelines, worked examples, and the mistakes that undermine a macro plan.
The single most important macro is protein. Get that right and the rest is fine-tuning to your preferences and training.
How macros are calculated
Calories per gram: Protein = 4 | Carbs = 4 | Fat = 9 Protein (g) = weight(kg) x 1.6-2.2 Fat (g) = 25-30% of calories / 9 Carbs (g) = remaining calories / 4
Each macro has a fixed calorie value: protein and carbs are 4 kcal per gram, fat is 9. The standard method sets protein first (from body weight), fat next (a percentage of calories for hormones and health), and lets carbohydrate fill whatever calories remain. This guarantees enough protein and fat while flexing carbs to your training needs.
Worked example
- Goal 2,000 kcal, body weight 70 kg, moderate protein at 2.0 g/kg.
- Protein = 70 x 2.0 = 140 g = 560 kcal.
- Fat = 28% of 2,000 = 560 kcal / 9 = about 62 g.
- Carbs = remaining 2,000 - 560 - 560 = 880 kcal / 4 = 220 g.
- Final macros: 140 g protein, 62 g fat, 220 g carbs.
Macro splits by goal
| Goal | Protein | Fat | Carbs | Notes |
|---|---|---|---|---|
| Fat loss (cut) | 30-40% | 25-30% | 30-40% | High protein preserves muscle, aids fullness |
| Maintenance | 25-30% | 25-30% | 40-50% | Balanced, sustainable |
| Muscle gain (bulk) | 25-30% | 20-25% | 45-55% | More carbs to fuel heavy training |
| Low-carb / keto | 25-30% | 55-65% | 5-10% | Very low carbs; fat is the main fuel |
Using this calculator and avoiding mistakes
- Enter your daily calorie goal (from the calorie or TDEE calculator) and your body weight.
- Set protein per kg (start around 1.8-2.2 g/kg) and a fat percentage (25-30%).
- Read your gram targets for protein, fat and carbs.
- Track intake against these, prioritising hitting protein; treat carbs and fat as flexible within your calorie budget.
Common mistakes
- Under-eating protein - the most common and costly error, especially when cutting.
- Obsessing over an exact carb-to-fat ratio when calories and protein matter far more.
- Cutting fat too low (below ~0.5 g/kg), which can affect hormones and vitamin absorption.
- Ignoring that macro grams must still add up to your calorie target - the two are linked.
- Treating 'flexible dieting' as license to fill macros with junk; food quality still affects health and satiety.
Frequently asked questions
Glossary
- Macronutrients
- Protein, carbohydrate and fat - the calorie-providing nutrients.
- Protein
- 4 kcal/g; builds and preserves muscle, most filling macro.
- Carbohydrate
- 4 kcal/g; the body's main training fuel.
- Fat
- 9 kcal/g; essential for hormones and vitamin absorption.
- Macro split
- The percentage of calories from each macronutrient.
- IIFYM
- 'If It Fits Your Macros' - flexible dieting within macro targets.
- g/kg
- Grams per kilogram of body weight - how protein targets are set.
- Micronutrients
- Vitamins and minerals - needed too, but calorie-free.
Key takeaways
Macros turn a calorie goal into a body-composition plan: protein (4 kcal/g) set first by body weight (1.6-2.2 g/kg), fat (9 kcal/g) at 25-30% of calories, and carbs (4 kcal/g) filling the rest. Splits shift by goal - higher protein for cutting, more carbs for bulking - but protein is the constant priority across all of them. Nail protein and calories, keep fat above a sensible floor, and flex carbs to your training and taste.
Enter your calorie goal and body weight above for your protein, carb and fat targets; then track protein first and let carbs and fat flex within your calorie budget.