Building muscle comes down to two things done consistently: eating slightly above what your body burns, and training with enough intensity to give it a reason to grow. Get the surplus too big and you’ll mostly gain fat; get it too small and you’ll barely grow at all. This guide walks you through it in order: your numbers, your surplus, your protein and macro targets, and how to actually track progress by strength, not just the scale.
Meet Robin
Robin is 20, 186cm, and started this process at 60kg, training four days a week. He’s used throughout our articles as a real-world example of lean muscle gain — not a “dirty bulk” chasing the scale, but a controlled surplus paired with progressive strength training. You’ll see his numbers referenced as you go through the steps below.
Step 1: Know Your Numbers
Just like fat loss, muscle gain starts with your TDEE (Total Daily Energy Expenditure) — the real number of calories your body burns in a full day. For fat loss you’d eat below it; for muscle gain, you’ll eat slightly above it. Either way, TDEE is the baseline everything else in this guide is built from.
For Robin, using the Mifflin-St Jeor equation, his BMR comes out to roughly 1,687 calories. Factoring in his training four days a week (a “moderately active” multiplier of ×1.55), his TDEE lands at approximately 2,615 calories. That number — not a random “eat more” instruction — is what his surplus in Step 2 is calculated from.
Want the full explanation behind the number, including the exact formula used?
Step 2: Set Your Surplus
Once you know your TDEE, the muscle-gain math is the mirror image of fat loss: eat consistently 200–400 calories above it, not drastically more. A surplus this size is enough to fuel muscle growth without piling on unnecessary fat — the bigger the surplus beyond this range, the more of the gain tends to be fat rather than muscle, since your body can only build muscle at a limited rate regardless of how much extra you eat.
For Robin, that means a target somewhere between 2,815 and 3,015 calories a day. If the scale is climbing faster than roughly 0.25–0.5kg a week, the surplus is likely too large and mostly adding fat rather than muscle — worth scaling back rather than assuming “more is better.”
Step 3: Hit Your Protein and Macro Targets
A surplus alone doesn’t build muscle — training does that. What the surplus and protein intake together determine is whether the tissue you gain is actually muscle. Protein needs during a muscle-building phase sit in a similar range to fat loss, roughly 1.6–2.2 grams per kilogram of bodyweight, since it’s the direct building block your body uses for muscle repair and growth.
For Robin at 60kg, that works out to 96–132g of protein a day. Beyond protein, getting enough carbohydrate matters more for muscle gain than it does for fat loss — carbs fuel the training sessions that actually stimulate growth in the first place, so cutting them too low while trying to build muscle tends to backfire on performance in the gym.
- Complete Guide to Protein: Requirements by Age
- How to Calculate Macros for Beginners — Step by Step Guide
Step 4: Track Strength, Not Just the Scale
For fat loss, the scale is unreliable because it can’t separate fat from water and muscle. For muscle gain, it’s unreliable for a different reason: it can’t tell you whether the weight you’re adding is muscle or fat at all. The more useful signal is whether you’re getting stronger — if your lifts are climbing over weeks and months, you’re building muscle, regardless of exactly what the scale says on any given day.
Track your estimated one-rep max on your main lifts every 4–6 weeks rather than testing it constantly — frequent max-effort testing adds injury risk without adding useful information, since strength doesn’t meaningfully change week to week.
Common Mistakes to Avoid
- “Dirty bulking” — eating far beyond your surplus target on the assumption that more calories always means more muscle. Past a point, extra calories just become fat.
- Undertracking protein — a surplus without enough protein still limits how much of what you gain is actually muscle.
- Judging progress by the scale alone — weight can climb from fat gain just as easily as from muscle; strength trends are the more reliable signal.
- Skipping progressive overload — a surplus and protein target don’t build muscle by themselves; your training needs to keep demanding more from your body over time.
Related Reading
- 5 Best Exercises for Beginners Starting From Zero
- Common Injuries in Your 20s and 30s — and How to Prevent Them
Ready to Start?
The first step is knowing your number. Calculate your TDEE now, then follow the steps above in order.
Disclaimer: This guide is for informational and educational purposes only and does not constitute medical or nutritional advice. Individual results vary; always consult a qualified healthcare professional or coach before starting a training and nutrition program.