Macro Calculator

What Macros Actually Do

Protein (4 kcal/g) builds and repairs muscle, supports immune function, and is the most satiating macronutrient per calorie. Carbohydrates (4 kcal/g) are the primary fuel for high-intensity effort — the brain and fast-twitch muscle fibres prefer glucose. Fat (9 kcal/g) supports hormone production, fat-soluble vitamin absorption, and provides sustained energy during low-intensity activity. All three are essential. The ratio between them determines substrate utilisation, hunger levels, and performance — but total calories determine weight direction regardless of macro split.

Flexible Dieting (IIFYM)

If It Fits Your Macros (IIFYM) treats food as macronutrient information rather than categorising foods as "clean" or "dirty." Research consistently shows adherence determines outcomes more than specific food choices: a diet you can stick to beats a theoretically optimal one you abandon in three weeks. IIFYM lets you eat a wide variety of foods while hitting targets, reducing the psychological cost of strict restriction. The practical limit is micronutrient density — hitting macro numbers entirely with processed food misses vitamins, minerals, and fibre that whole foods provide. Aim for 80–90% whole foods and use the remainder for flexibility.

Choosing the Right Split for Your Goal

For fat loss, high protein (0.8–1g per lb bodyweight) preserves muscle mass in a deficit. A 40/30/30 protein/carb/fat split works well for most. For muscle gain, higher carbs support training intensity and glycogen replenishment — a 30/45/25 split is common. Ketogenic diets (under 50g carbs/day) produce fat loss comparable to other approaches when calories are matched, but can impair high-intensity performance. Low-carb at 100–150g carbs/day is a practical middle ground for people who find fat more satiating without going fully ketogenic.

How to Track Macros in Practice

Weighing food with a digital kitchen scale is significantly more accurate than measuring cups — volumes vary dramatically with food density. Apps like Cronometer (most accurate nutritional database), MyFitnessPal (largest food database), and Carb Manager (keto-focused) all scan barcodes and track macros. The first week of tracking is typically revealing: most people discover they've been dramatically underestimating calorie-dense foods like oils, nuts, and dressings. You don't need to track forever — 4–8 weeks builds enough intuition about portion sizes to maintain targets without daily logging.