Macronutrient Split Calculator (Protein, Carbs, Fat)

Macronutrient Guide

Why Macros Matter?

Three macronutrients provide all dietary calories: protein (4 kcal/g), carbohydrate (4 kcal/g), fat (9 kcal/g). Alcohol (7 kcal/g) is a fourth source. Different macros serve different roles: protein is mainly structural (muscle, organs, enzymes) — minimum 0.8 g/kg for sedentary adults, much higher for trained populations. Carbs are the primary fuel for higher-intensity exercise. Fat is essential for hormone production, vitamin absorption, cell membranes. Calorie balance determines whether you gain, lose, or maintain weight, regardless of the specific macro split chosen — but the split still affects satiety, muscle retention, and how sustainable a diet feels day to day.

What's the key thing to understand about Protein Targets by Goal?

Sedentary adult RDA: 0.8 g/kg/day (preserve nitrogen balance, prevent deficiency). Real-world minimum for healthy active adult: 1.2-1.4 g/kg. Resistance training for muscle gain: 1.6-2.2 g/kg/day. Meta-analyses suggest 1.6 g/kg as a practical threshold beyond which additional protein adds little to muscle synthesis. Fat loss (preserving muscle in deficit): 1.8-2.4 g/kg. Higher protein particularly important when calorie-restricted to minimise muscle loss. Older adults (60+): 1.4-1.6 g/kg minimum, to preserve lean mass and support the higher protein turnover that comes with age-related muscle loss.

What do I need to know about Carbohydrate Targets?

Highly variable based on activity. Sedentary: 2-3 g/kg/day for general health (~150-200g for a 75kg adult). Mostly from vegetables, fruits, whole grains. Resistance training: 3-5 g/kg/day. Sufficient for glycogen replenishment between training sessions. Endurance training: 5-8 g/kg/day during heavy training blocks. Marathon training, cycling base building. Carb periodisation: vary intake daily to match training. Higher carbs on hard training days, lower on rest days. Helps body composition for endurance athletes managing glycogen stores around key training sessions, ensuring enough fuel is available for the hardest efforts without unnecessary excess on easier days.

What do I need to know about Fat Intake?

Minimum healthy intake: 0.5-0.8 g/kg/day (~40-60g for a 75kg adult). Below this risks hormonal disruption, especially female reproductive hormones, sex hormones in both sexes. Typical: 0.8-1.5 g/kg/day. Provides essential fatty acids and supports hormone function. Higher (1.5-3 g/kg): ketogenic or very-low-carb approaches. Quality matters: prioritise: olive oil, avocados, nuts, fatty fish (salmon, mackerel, sardines), eggs, full-fat dairy. Reduce: industrial seed oils such as corn and soybean, and trans fats and heavily processed foods, since these are consistently linked to worse cardiovascular outcomes than natural fat sources.