Macro Calculator — Calculate Your Ideal Macros

What Are Macros?

Macronutrients — protein, carbohydrates, and fat — are the three nutrients your body needs in large quantities. Each provides energy measured in calories:

• Protein: 4 calories per gram. Builds and repairs muscle tissue. Essential for recovery from resistance training.
• Carbohydrates: 4 calories per gram. Your body's preferred fuel source for high-intensity exercise like lifting.
• Fat: 9 calories per gram. Supports hormone production (including testosterone), absorbs fat-soluble vitamins, and provides sustained energy.

Tracking macros — not just calories — ensures you're getting enough of each nutrient to support your training and body composition goals.

How Much Protein Do You Need?

Protein is the most important macro for anyone who lifts. The International Society of Sports Nutrition (ISSN) position stand (Campbell et al., 2017) recommends 1.4-2.0 g/kg/day for resistance-trained individuals.

During a caloric deficit, protein needs increase. A 2018 meta-analysis by Morton et al. found that 1.6 g/kg/day was sufficient to maximize muscle protein synthesis in a surplus, but during a cut, higher intakes (1.8-2.2 g/kg) help preserve lean mass. A landmark study by Helms et al. (2014) recommended up to 2.3-3.1 g/kg of lean body mass for natural bodybuilders during contest prep.

This calculator uses conservative, well-supported defaults: 2.0 g/kg for fat loss, 1.8 g/kg for muscle gain, and 1.6 g/kg for maintenance.

Fat: The Minimum Your Body Needs

Dietary fat is not the enemy — it's essential. Fat below 15% of total calories can disrupt hormone production, particularly testosterone in men and estrogen in women. Fat-soluble vitamins (A, D, E, K) require dietary fat for absorption.

A practical minimum is 0.5 g/kg bodyweight. Most lifters do well at 0.8-1.0 g/kg, which provides hormonal support without eating into your carb budget. This calculator defaults to 0.8 g/kg during cuts and 1.0 g/kg for maintenance and gaining.

Carbs: Your Training Fuel

Carbohydrates fill the remaining calories after protein and fat are set. This isn't arbitrary — it's the most flexible macro. Protein is set by muscle needs, fat by hormonal minimums, and carbs adjust to hit your calorie target.

For strength athletes, carbs matter more than many realize. A 2018 study by Escobar et al. found that low-carb diets impaired resistance training performance compared to higher-carb approaches at the same caloric intake. Glycogen — stored from carbohydrates — is the primary fuel for sets of 6-20 reps.

During a cut, carbs get lower because protein and fat are protected. During a bulk, the surplus goes almost entirely to carbs, which fuels harder training sessions and better recovery.

Adjusting Macros Over Time

These numbers are a starting point, not a permanent prescription. Here's how to dial them in:

1. Week 1-2: Follow the calculated macros consistently. Track everything.
2. Week 3-4: Assess results. If cutting, are you losing 0.5-1% bodyweight per week? If gaining, are you gaining 0.25-0.5% per week?
3. Adjust: If progress is too fast, add 100-200 calories (mostly carbs). Too slow, subtract 100-200 calories (mostly carbs). Never cut protein.

RepStack tracks your bodyweight, training volume, and estimated 1RM over time — giving you the data to make informed adjustments instead of guessing.

Tips for Hitting Your Macros

• Prioritize protein at every meal. Spread 30-50g across 3-5 meals for optimal muscle protein synthesis.
• Eat carbs around training. Pre- and post-workout meals should be carb-heavy for energy and recovery.
• Don't fear fat. Healthy fats (avocado, nuts, olive oil, fatty fish) support hormones and satiety.
• Weekly averages matter more than daily perfection. A day over on carbs and under on fat balances out.
• Use the TDEE Calculator first to get your maintenance calories, then come back here for the macro split.