Every fitness goal — bulking, cutting, recomposition, performance, or maintenance — comes down to the same three levers: how much protein, carbs, and fat you eat each day. This is the complete macronutrient guide: how to calculate the right split for your goal, what each macro actually does in the body, and how to adjust across a 12-month training cycle. Everything here is anchored to peer-reviewed evidence (Morton 2018, Helms 2014, Iraki 2019, Aragon-Schoenfeld) rather than diet-culture heuristics.

What Macros Are and Why They Matter

Macronutrients are the three energy-providing components of food:

  • Protein: 4 kcal per gram. Builds and repairs tissue, provides amino acids, contributes to satiety.
  • Carbohydrates: 4 kcal per gram. Primary fuel for training and brain function, replenishes muscle glycogen.
  • Fat: 9 kcal per gram. Hormone production, absorbs fat-soluble vitamins (A, D, E, K), long-duration energy.

Total calories determine whether you gain, lose, or hold weight. Macro split determines what tissue you gain or lose. A 500 kcal surplus eaten as 100% carbs builds primarily fat and glycogen; the same 500 kcal surplus with 2 g/kg protein builds muscle. This is why macros exist as a concept separate from calorie counting.

The Complete Macro Calculation Workflow

Step 1 — Calculate TDEE

Every macro plan starts with Total Daily Energy Expenditure. Use the Mifflin-St Jeor formula (validated in the 2005 accuracy analysis):

  • Men BMR: (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
  • Women BMR: (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
  • TDEE: BMR × activity multiplier (1.2 sedentary to 1.9 extremely active)

Full breakdown of activity multipliers and how to verify your real TDEE in the TDEE complete guide.

Step 2 — Apply Goal Adjustment

  • Fat loss: TDEE − 15-25% (typically 300-600 kcal below)
  • Maintenance / recomp: TDEE ±5%
  • Lean bulk: TDEE + 200-300 kcal
  • Standard bulk: TDEE + 400-500 kcal
  • Aggressive bulk: TDEE + 700+ kcal (fast strength gain, more fat)

Step 3 — Lock Protein First

Protein is the load-bearing macro — everything else adjusts around it. Set protein by goal:

  • Fat loss (cut): 2.0-2.4 g/kg bodyweight
  • Muscle gain (bulk): 1.8-2.2 g/kg
  • Recomposition: 2.0-2.2 g/kg
  • Maintenance: 1.4-1.8 g/kg (or up to 1.6 g/kg lean mass)

These come from the Morton et al. 2018 meta-analysis of 49 studies. Above 2.2 g/kg during a bulk, additional protein produces diminishing returns; during a cut, higher protein (up to 2.4 g/kg) helps preserve lean mass in the deficit.

Step 4 — Set Fat (Minimum Threshold)

Fat has a floor for hormone function and vitamin absorption:

  • Minimum: 0.6-0.8 g/kg bodyweight (below this, hormone function degrades over weeks)
  • Standard: 0.9-1.1 g/kg
  • Higher-fat approach: 1.2-1.5 g/kg (for people who thrive on lower-carb intakes)

Iraki et al. (2019) recommend a minimum of 20% of total calories from fat during any dieting phase to preserve testosterone and menstrual function.

Step 5 — Fill Remaining Calories with Carbs

Once protein and fat are set, carbs get whatever is left in the calorie budget:

Remaining kcal = Target − (protein grams × 4) − (fat grams × 9)

Carbs grams = Remaining kcal ÷ 4

Carbs are the flexible macro — they scale up on training days for performance, down on rest days if calorie targets require it. Athletes running high volume will land at 4-7 g/kg carbs; sedentary dieters may sit at 2-3 g/kg.

Worked Example: 80 kg Man, Muscle Gain

Male, 30 years, 178 cm, 80 kg, moderately active (1.55):

  1. BMR = (10 × 80) + (6.25 × 178) − (5 × 30) + 5 = 1,767 kcal
  2. TDEE = 1,767 × 1.55 = 2,739 kcal
  3. Bulk target = 2,739 + 300 = ~3,040 kcal
  4. Protein = 80 × 2.0 = 160 g = 640 kcal
  5. Fat = 80 × 1.0 = 80 g = 720 kcal
  6. Carbs = (3,040 − 640 − 720) ÷ 4 = 420 g

Final macros: 160P / 420C / 80F on 3,040 kcal. Full example variations in the macro calculator for muscle gain guide.

Worked Example: 65 kg Woman, Fat Loss

Female, 28 years, 165 cm, 65 kg, lightly active (1.375):

  1. BMR = (10 × 65) + (6.25 × 165) − (5 × 28) − 161 = 1,380 kcal
  2. TDEE = 1,380 × 1.375 = 1,898 kcal
  3. Cut target = 1,898 × 0.80 = ~1,520 kcal (−20% deficit)
  4. Protein = 65 × 2.2 = 143 g = 572 kcal
  5. Fat = 65 × 0.7 = 46 g = 414 kcal
  6. Carbs = (1,520 − 572 − 414) ÷ 4 = 134 g

Final macros: 143P / 134C / 46F on 1,520 kcal. Full example variations in macro calculator for fat loss.

Popular Macro Splits Explained

40/40/20 (Recomposition Standard)

40% protein / 40% carbs / 20% fat. Elevated protein for lean tissue, moderate carbs for training performance, floor-level fat. Works well for intermediate lifters maintaining bodyweight while trying to slowly reshape body composition.

40/30/30 (Zone Diet Legacy)

40% carbs / 30% protein / 30% fat. Popularized by the Zone Diet in the 1990s. Moderate everything — reasonable maintenance split, though most modern approaches push protein higher for lifters.

30/40/30 (Balanced Athletic)

30% protein / 40% carbs / 30% fat. Common recommendation for general athletic populations. Not optimized for aggressive muscle gain or fat loss but sustainable long-term.

Leangains 5:2 (Berkhan)

Martin Berkhan's Leangains split cycles macros: high carb / low fat on training days, low carb / higher fat on rest days, protein constant. See the Leangains macro calculator for the full protocol.

Keto (Low-Carb / High-Fat)

~70-75% fat / 20-25% protein / 5-10% carbs. Restricts carbs below 30-50 g/day to induce ketosis. Works for fat loss primarily via satiety and calorie displacement; not optimal for high-volume lifters due to reduced glycogen availability.

The Non-Negotiable: Protein First

Across all fitness goals, protein intake is the single macro that most directly affects outcomes. The Morton 2018 meta-analysis (49 RCTs, 1,863 subjects) established:

  • 1.6 g/kg is the threshold for maximum lean mass gain from resistance training
  • Above 1.6 g/kg produces small additional benefit; above 2.4 g/kg produces essentially none
  • During caloric deficit, higher protein (2.0-2.4 g/kg) preserves more lean mass
  • Distribution: 3-5 meals with 0.3-0.4 g/kg per meal maximizes protein synthesis

If you hit the protein target and rough calorie target, the exact carb/fat split matters far less than most content suggests. Protein first, calories second, everything else is fine-tuning.

How Macros Change Across Goals

Cutting Phase (12-16 Weeks)

  • Deficit: 20-25% below TDEE
  • Protein: 2.2-2.4 g/kg
  • Fat: 0.6-0.8 g/kg (minimum viable)
  • Carbs: fill remainder
  • Recalculate every 4 weeks as bodyweight drops

Bulking Phase (16-24 Weeks)

  • Surplus: +200-500 kcal above TDEE
  • Protein: 1.8-2.0 g/kg
  • Fat: 0.9-1.1 g/kg
  • Carbs: fill remainder (typically 4-7 g/kg for lifters)
  • Recalculate every 4-6 weeks as bodyweight climbs

Recomposition Phase (Ongoing)

  • Calories: at or ±5% of TDEE
  • Protein: 2.0-2.2 g/kg
  • Fat: 0.9-1.0 g/kg
  • Carbs: fill remainder
  • Expect slow progress — measured in months, not weeks

Maintenance / Off-Season

  • Calories: at TDEE
  • Protein: 1.4-1.8 g/kg
  • Fat: 0.8-1.2 g/kg
  • Carbs: whatever feels sustainable

Common Macro Calculation Mistakes

  • Setting protein too low. "1 g/lb" (~2.2 g/kg) is often over-prescribed for bulks but appropriate for cuts. Most people undershoot during dieting phases where protein matters most.
  • Fat below 0.6 g/kg for extended periods. Long-term ultra-low-fat cuts (below 15% of calories) suppress hormones. Add fat before dropping carbs further.
  • Using bodyweight instead of lean mass for protein. For very lean or very obese individuals, protein per kg of lean mass is more accurate than per kg of bodyweight.
  • Never recalculating. A macro plan from 6 months ago is stale — bodyweight has moved, activity has moved, TDEE has moved.
  • Chasing precision that doesn't exist. Hitting macros ±10 g/day is fine. Obsessing over ±1 g adds no benefit.

How Meal Timing Fits (or Doesn't) with Macros

The current evidence (Aragon-Schoenfeld 2013, Schoenfeld 2020):

  • Anabolic window: extends 4-6 hours around training. Post-workout protein within 30 minutes matters less than daily total.
  • Meal frequency: 3-5 meals per day is sufficient for maximizing protein synthesis. More frequent meals produce no additional benefit if daily totals are hit.
  • Pre-sleep protein: A 30-40 g casein or whole-food protein serving 1-2 hours before bed slightly increases overnight muscle protein synthesis (Res et al. 2012).
  • Carb timing: Around workouts is convenient but not required. Total daily carbs matter more than exact timing.

Popular Macro Approaches Compared

  • IIFYM (If It Fits Your Macros): Any food that fits daily macro targets. Maximum flexibility. Works for people with strong impulse control around trigger foods.
  • Flexible Dieting (RP-style): Structured macro targets with prescribed food quality ratios (80-90% whole foods, 10-20% flexibility). See Leangains-style variations.
  • Meal Plan (traditional): Prescribed exact foods and quantities. Zero flexibility but zero decision fatigue.
  • Intuitive Eating: No tracking; eat to hunger and satiety cues. Works for maintenance for some; unreliable for aggressive fat loss or muscle gain phases.

Which Macro Calculator Should You Actually Use?

Most macro calculators on the internet fall into one of four camps. Here is how the popular ones stack up on the two things that matter — which formula they use for TDEE and which protein research base they anchor to:

  • IIFYM.com: Mifflin-St Jeor for TDEE, generic 1 g/lb protein default (~2.2 g/kg). Reasonable starting point but no goal-specific adjustments and no calibration guidance.
  • AthleanX / Jeff Cavaliere content: No standalone calculator tool. Video-driven macro guidance anchored to Kouri 1995 for FFMI and Morton 2018 for protein. Higher protein (up to 2.4 g/kg) during cuts. See our Built With Science vs AthleanX comparison.
  • Built With Science / Jeremy Ethier: No dedicated calculator. Programmed macro splits inside paid programs, drawing from the same Morton and Helms research base. Emphasis on hypertrophy periodization rather than free tools.
  • Legion Athletics / Muscle for Life (Mike Matthews): Mifflin-St Jeor with 1 g/lb protein default and prescribed 1 g/lb bodyweight. Simplified for beginners; less granular for advanced lifters.
  • Leangains / Martin Berkhan: Cyclical macros — high on training days, lower on rest days, protein constant. Best for lean-recomp phases. Full protocol in the Leangains macro calculator.
  • FFMI Check Macro Matrix (this site): Mifflin-St Jeor TDEE, Morton 2018 + Helms 2014 protein ranges, goal-specific splits (cut / recomp / lean bulk / bulk / aggressive), no signup. Same evidence base as AthleanX and Built With Science, delivered as a free tool.

The truth few macro calculators admit: they all use the same 3-4 underlying formulas. The differences are in defaults (which multiplier the calculator picks for you), presentation (how much guidance vs raw numbers), and calibration guidance (whether they teach you to adjust after 2 weeks). If a calculator gives you a number and disappears, it is undertrained regardless of the brand behind it.

Related Cluster Reading

Bottom Line

Every macro plan reduces to five steps: calculate TDEE, apply your goal adjustment, lock protein at 1.8-2.4 g/kg based on phase, set fat at 0.7-1.1 g/kg, and fill carbs with what's left. Protein is the non-negotiable input; everything else is fine-tuning around it. Recalculate every 4-6 weeks as bodyweight and activity shift, and stop treating macros as more precise than they need to be — hitting daily totals within ±10 g is a rounding error, not a failure. The plan that works is the plan that gets executed for 12+ weeks straight.