How to Calculate Macros for Muscle Gain (Evidence-Based Guide)

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Getting Started

The Bulk That Actually Works

You've probably heard it before: "Just eat big to get big." And maybe you've tried it. Piled on the calories, watched the scale climb, then realised most of what you gained wasn't muscle.

Or maybe you've gone the other way. Stayed lean, kept calories modest, and wondered why you're not making progress despite training hard.

Here's the reality: once you're past the beginner stage, building meaningful muscle without a calorie surplus is extremely difficult.

Untrained individuals can gain muscle at maintenance, or even in a deficit, because their bodies respond dramatically to a new stimulus. But if you've been training consistently for a year or more, that window closes. Your body needs extra energy to fuel the muscle-building process.

The question isn't whether to eat more. It's how much more.

The Problem with "Eating Big"

Some fat gain during a building phase is unavoidable. When you're in a surplus, your body stores some energy as fat. That's basic physiology.

But here's what the research shows: a bigger surplus doesn't mean more muscle. It mostly means more fat.

Studies comparing moderate surpluses to large surpluses consistently find similar lean mass gains, but dramatically different fat gains. One study found a fivefold increase in fat mass with a larger surplus, with no significant difference in muscle or strength [1].

The goal isn't to eat as much as possible. It's to supply enough surplus to support maximal muscle growth, without the excess spilling over into unnecessary fat storage.

Here's how to calculate it properly.

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Setting Your Targets

Protein: 1.8-2.2 g/kg of bodyweight

Lower than fat loss. That's not a typo.

During a surplus, you don't need as much protein to protect muscle. You're not in a catabolic state. The research supports 1.6-2.2 g/kg for building phases. Pushing higher just displaces carbs that could fuel your training.

How to calculate:

• Multiply your weight in kg by 2.0
• Cap at 2.4 g/kg or 30% of calories (whichever is lower)
• Keep stable when adding calories (it's already sufficient)

Fat: 0.8-1.0 g/kg of bodyweight

Moderate intake to support hormones and overall health. No need to restrict during building, but no need to go overboard either.

How to calculate:

• Multiply your weight in kg by 0.9
• Set a floor of 0.6 g/kg (minimum 20% of calories)
• Keep below ~35% of calories to leave room for carbs

Carbohydrates: The remainder (floor: 3.0 g/kg)

This is where building differs most from fat loss. Carbs fuel training, support recovery, and help shuttle nutrients into muscle. During a surplus, extra calories primarily go here.

How to calculate:

• Take remaining calories after protein and fat
• Divide by 4 (calories per gram)
• Ensure you're hitting at least 3.0 g/kg (higher is fine)

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Step-by-Step Calculation

Let's walk through an example: 75 kg person at 2,800 calories (moderate surplus).

Step 1: Protein

75 kg × 2.0 g/kg = 150g protein
150g × 4 calories = 600 calories

Check: 600 ÷ 2,800 = 21% (under 30% cap ✓)

Step 2: Fat

75 kg × 0.9 g/kg = 68g fat
68g × 9 calories = 612 calories

Check: 612 ÷ 2,800 = 22% (above 20% floor ✓)

Step 3: Carbs

Remaining: 2,800 - 600 - 612 = 1,588 calories
1,588 ÷ 4 = 397g carbs

Check floor: 75 kg × 3.0 = 225g minimum
397g > 225g ✓

Final Macros

Macro	Grams	Calories	%
Protein	150g	600	21%
Fat	68g	612	22%
Carbs	397g	1,588	57%

Notice how carbs dominate. That's intentional: they're fuelling your training and recovery.

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Rate of Gain: The Sweet Spot

Target 0.25-0.5% of bodyweight per week.

For a 75 kg person:

• Minimum: 0.19 kg/week (~0.75 kg/month)
• Maximum: 0.38 kg/week (~1.5 kg/month)

Gaining faster? You're mostly adding fat. Scale back the surplus.

Gaining slower? You might be leaving muscle on the table, or not actually in a surplus.

Advanced lifters: Be more conservative. Aim for 0.25% or less. Your potential rate of muscle gain is lower, so a larger surplus just means more fat.

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When Weight Isn't Moving

If the scale isn't trending up after 2-3 weeks of consistent tracking, add calories strategically:

1. Increase Carbs First

• Add 60-80% of any increase to carbs
• Example: Adding 200 calories → 150 calories to carbs (37g)

2. Add Some Fat

• Remaining 20-40% goes to fat
• Example: 50 calories to fat (6g)

3. Keep Protein Stable

• Already sufficient for muscle growth
• No need to increase

Example Adjustment (+200 calories)

Starting: 150g protein, 68g fat, 397g carbs (2,800 cal)

Carb increase: 150 cal ÷ 4 = 37g Fat increase: 50 cal ÷ 9 = 6g

New macros: 150g protein, 74g fat, 434g carbs (3,000 cal)

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Common Mistakes to Avoid

Mistake 1: Too Much Protein

At 3,000 calories, some calculators suggest 300g+ protein. That's expensive, hard to eat, and research shows no benefit beyond ~2.2 g/kg. Those calories are better spent on carbs.

Mistake 2: Too Large a Surplus

A 500-calorie surplus doesn't build twice as much muscle as 250. It builds the same muscle plus extra fat. Start conservative and adjust based on actual rate of gain.

Mistake 3: Ignoring Training Status

Beginners can tolerate larger surpluses. Advanced lifters need smaller ones. If you've been training for 5+ years, a 10% surplus is probably plenty.

Mistake 4: Restricting Carbs

Building phases aren't the time for low-carb approaches. Studies consistently show inferior muscle gain outcomes with carbohydrate restriction during resistance training [2].

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Want to understand the research behind these numbers? Keep reading.

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The Science

Do You Actually Need a Surplus?

For beginners, not necessarily. Multiple studies show untrained individuals can gain muscle in a deficit, particularly with adequate protein [3].

But for trained individuals, the picture changes. A study on trained bodybuilders found those in a surplus gained more lean mass (0.5 kg vs 0.0 kg) compared to maintenance [4]. The mechanism: an augmented muscle protein synthetic response during positive energy balance.

The challenge is that surplus also drives fat storage. The same study found the surplus group gained 1.1 kg of fat vs 0.2 kg at maintenance. This is the fundamental tension: you need surplus for optimal growth, but excess just makes you fatter.

How Much Surplus?

A landmark study compared elite athletes following a higher surplus (~600 kcal/day extra) to a moderate approach [1]. Result: fivefold greater fat gain in the higher surplus group, with no significant difference in lean mass or strength.

More recently, researchers compared 5%, 15%, and maintenance intakes in trained lifters [5]. Same finding: no significant differences in muscle gains between groups, but more body fat in the higher surplus group.

The evidence-based recommendation: 10-20% surplus with 0.25-0.5% bodyweight gain per week [6]. Advanced athletes should be even more conservative.

Why Less Protein Than Fat Loss?

During energy restriction, elevated protein (2.3-3.1 g/kg lean mass) preserves muscle in a catabolic state [7]. During a surplus, you're not fighting catabolism. Adequate energy supports an anabolic environment.

Research recommends 1.6-2.2 g/kg for building phases, noting that "consuming beyond this amount would not induce further benefits" [6]. Higher protein just displaces carbohydrates that improve training performance.

Why Carbs Matter Here

Unlike fat loss where carbs are flexible, building phases prioritise them. The recommendation: ≥3-5 g/kg/day to support resistance training demands [6].

Studies comparing low-carb to moderate/high-carb approaches during resistance training consistently show inferior muscle gain with carb restriction [2]. The practical conclusion: don't restrict carbs during a building phase.

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References

1. Garthe I, et al. Effect of nutritional intervention on body composition and performance in elite athletes. Eur J Sport Sci. 2013;13(3):295-303.
   doi:10.1080/17461391.2011.643923

2. Helms ER, et al. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr. 2014;11:20.
   doi:10.1186/1550-2783-11-20

3. Barakat C, et al. Body Recomposition: Can Trained Individuals Build Muscle and Lose Fat at the Same Time? Strength Cond J. 2020;42(5):7-21.
   doi:10.1519/SSC.0000000000000584

4. Ribeiro AS, et al. Effects of Different Dietary Energy Intake Following Resistance Training on Muscle Mass and Body Fat in Bodybuilders: A Pilot Study. J Hum Kinet. 2019;70:125-134.
   doi:10.2478/hukin-2019-0038

5. Helms ER, et al. Effect of Small and Large Energy Surpluses on Strength, Muscle, and Skinfold Thickness in Resistance-Trained Individuals. Sports Med Open. 2023;9:104.
   doi:10.1186/s40798-023-00651-y

6. Iraki J, et al. Nutrition Recommendations for Bodybuilders in the Off-Season: A Narrative Review. Sports. 2019;7(7):154.
   doi:10.3390/sports7070154

7. Roberts BM, et al. Nutritional Recommendations for Physique Athletes. J Hum Kinet. 2020;71:79-108.
   doi:10.2478/hukin-2019-0096

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Skip the Spreadsheets

This is exactly the methodology TrainingFuel implements automatically, but without the spreadsheets. We calculate your targets, monitor your rate of gain, and adjust when you're gaining too fast (excess fat) or too slow (leaving muscle on the table).

No manual calculations. No guessing if your surplus is right. Just consistent progress toward your goal.