Macro Calculator — Protein, Carbs & Fat

What Is This Calculator?

Macronutrients — protein, carbohydrates, and fat — are the three main nutrients that provide energy. Getting the right balance of each for your specific goal can dramatically improve your results, whether you are trying to lose fat, maintain weight, or build muscle.

How to Use This Calculator

Enter your details into the calculator above and click the calculate button. Results are instant and personalised to your specific inputs. All formulas are evidence-based and transparently explained.

Why Macros Matter More Than Calories Alone

While total calorie intake determines whether you gain, lose, or maintain weight, the distribution of those calories across protein, carbohydrates, and fat determines your body composition outcome — specifically how much of your weight change is fat versus muscle. Two people can eat the same 1,800 calories per day and get very different results: one loses fat while preserving muscle; the other loses fat and muscle in roughly equal proportions. The difference is almost entirely protein intake.

Each macronutrient has a different caloric density and metabolic role. Protein (4 kcal/g) is the building block for muscle, enzymes, and immune function, and has the highest thermic effect of any macronutrient (25–30% of its calories are burned during digestion). Carbohydrates (4 kcal/g) are the primary fuel for high-intensity exercise and the preferred fuel for the brain. Fat (9 kcal/g) is essential for hormone synthesis, fat-soluble vitamin absorption, and cell membrane integrity.

How the Calculator Sets Your Macros

Our macro calculator follows a three-step process. First, it calculates your TDEE using the Mifflin-St Jeor equation multiplied by your activity factor. Second, it adjusts calories for your goal — a 500 kcal deficit for cutting, maintenance for maintaining, or a 300 kcal surplus for bulking. Third, it allocates macros: protein is set at 1.6g/kg for maintenance or 2.0g/kg for cut and bulk phases; fat is set at 28% of total calories to ensure hormonal health; remaining calories fill carbohydrates.

The protein targets are grounded in a robust body of research. A 2017 systematic review in the British Journal of Sports Medicine (Morton et al.) found that protein intakes above 1.62g/kg/day produce no additional muscle protein synthesis benefits in trained individuals. However, for those in a caloric deficit — where muscle breakdown risk is elevated — intakes at the higher end (2.0–2.2g/kg) provide a meaningful protective effect.

Practical Macro Tracking

You do not need to track all three macros to benefit from this information. The single most impactful habit is hitting your daily protein target — research shows this alone, combined with calorie awareness, produces most of the body composition benefits of full macro tracking. If you only track one thing, make it protein. Use apps like Cronometer, MyFitnessPal, or Easy Diet Diary (popular in Australia) to log your intake. Consistency over weeks and months matters far more than perfection on any single day.