Building muscle takes energy. New muscle tissue has to be built, and hard training needs fuel. That is why most people build muscle fastest when they eat a little more than they burn.
The key word is “little”. Eat too much and the extra becomes fat, not muscle.
Key points
- Start from your maintenance calories, then add about 250–500 kcal a day.
- Aim to gain about 0.25–0.5% of your body weight per week.
- Beginners can use a bigger surplus; experienced lifters do better with a smaller one.
- Keep protein at 1.6–2.2 g/kg and train with progressive overload.
Step 1: Find your maintenance calories
Your maintenance calories, or TDEE, is the amount you burn in a day. It is your starting point. The TDEE calculator estimates it from your age, sex, size and activity level.
Step 2: Add a small surplus
Most people do well with a surplus of 250–500 kcal a day, or roughly 10% above maintenance.
| Training experience | Suggested surplus | Why |
|---|---|---|
| Beginner (under 1 year) | 300–500 kcal | Muscle grows fastest early on |
| Intermediate (1–3 years) | 250–350 kcal | Slower gains, less room for extra energy |
| Advanced (3+ years) | 150–250 kcal | Very slow gains; a large surplus mostly adds fat |
The calorie calculator gives you a lean bulk (+250 kcal) and standard bulk (+500 kcal) target.
Step 3: Aim for a slow rate of gain
A review of nutrition for bodybuilders suggests gaining about 0.25–0.5% of body weight per week. For an 80 kg (176 lb) person that is 0.2–0.4 kg (0.5–1 lb) a week, or about 1–1.5 kg a month.
Weigh yourself several times a week at the same time of day, and compare weekly averages. Daily weight jumps around with water, salt and food in your gut; the trend is what matters.
Step 4: Adjust every 2–3 weeks
- Gaining too slowly (less than 0.25% a week): add 100–200 kcal a day.
- Gaining too fast (more than 0.5% a week, or your waist is growing quickly): remove 100–200 kcal.
- On track: keep going. Your maintenance rises slowly as you get heavier, so expect small adjustments over time.
What about macros?
Calories set the pace; macros shape the result.
- Protein: 1.6–2.2 g per kg of body weight. See how much protein to build muscle.
- Fat: about 20–30% of calories.
- Carbs: the rest. Carbs fuel hard training and make a surplus easier to eat.
The macro calculator turns your calories into grams.
Do you need a surplus at all?
Not always. A 2019 review concluded that a surplus is not strictly required to build muscle, but it likely makes gains easier, especially for trained people. Beginners, people returning after a break and those with more body fat can often build muscle and lose fat at the same time. That is called body recomposition.
If that describes you, eating at maintenance or in a small deficit with high protein and good training can work well. Read bulking vs cutting to decide which approach fits.
Lean bulk vs dirty bulk
A “dirty bulk” means eating as much as possible to gain weight fast. It does build muscle, but not faster than a moderate surplus, and much more of the gain is fat. That fat then has to come off later in a diet, which costs time and some of your hard-earned muscle.
A lean bulk takes patience but gets you further for the same effort.
Summary
Find your maintenance, add 250–500 kcal, gain about 0.25–0.5% of body weight per week, and adjust based on your weekly average. Combine that with enough protein and progressive training, and most of what you gain will be muscle.