What Is Macro Tracking (IIFYM)?
Macro tracking: often called "If It Fits Your Macros" (IIFYM) or flexible dieting: is a nutrition approach where you hit daily gram targets for protein, carbohydrates, and fat rather than following a rigid meal plan. Any food can be eaten as long as your macro totals for the day are met.
This approach is more sustainable than eliminating entire food groups because it removes the psychological "forbidden food" effect. Research consistently shows that dietary adherence is the single strongest predictor of long-term success: and a flexible approach dramatically improves adherence.
How Macro Splits Are Calculated
The calculator first determines your TDEE (Total Daily Energy Expenditure) using the Mifflin-St Jeor equation plus an activity multiplier. It then divides those calories into protein, carbohydrate, and fat proportions based on your goal:
- Fat loss (40/30/30): Higher protein preserves muscle mass during the deficit. Moderate carbs sustain training performance. Fat fills the remaining calories.
- Maintenance (30/40/30): Balanced split supporting general health and sustainable eating patterns at calorie equilibrium.
- Muscle gain (30/45/25): More carbohydrates to fuel resistance training sessions and promote glycogen replenishment, which supports recovery and growth.
How to Track Your Macros Effectively
Use a food logging app: MyFitnessPal, Cronometer, and MacroFactor are the most popular. Weigh food on a kitchen scale rather than estimating portion sizes; visual estimates are notoriously inaccurate and account for most tracking errors.
Prioritise hitting your protein target every day. If your carbs or fat are slightly off, total calories and protein will drive 90% of your results. Once protein is consistently met, refine carbs and fat.
Frequently Asked Questions
What are macros?
Macros (macronutrients) are the three main nutrient categories that provide calories: protein (4 kcal/g), carbohydrates (4 kcal/g), and fat (9 kcal/g). Every food you eat is made up of some combination of these three. Tracking macros means hitting specific gram targets for each, rather than just counting total calories.
How do I use my macro results?
Use a food tracking app such as MyFitnessPal or Cronometer to log everything you eat. The app will show your protein, carbs, and fat totals for the day. Aim to hit (or come close to) your targets for each macro. Total calories matter most, but hitting protein is the highest priority.
Why is protein the most important macro?
Protein is the only macronutrient that builds and repairs muscle tissue. It also has the highest thermic effect (you burn 20–30% of protein calories just digesting it) and is the most satiating macro. For most goals: fat loss, muscle gain, or maintenance: hitting your protein target is the single most important macro priority.
Can I adjust the macro split?
Yes. The splits this calculator uses (e.g. 40/30/30 for fat loss) are evidence-based starting points, not rigid rules. Some people do well on lower carb approaches; others perform better with more carbs and less fat. Keep protein high and adjust carbs and fat to your preference and food tolerances.