Bulking means eating in a controlled calorie surplus to build muscle. The surplus supplies the energy and building blocks for growth, but size it wrong and you gain far more fat than muscle. This muscle gain macro calculator sizes your surplus and splits it into protein, carb, and fat targets, so you grow lean instead of just gaining weight.
Enter your details below. For a lean bulk, choose the “Lean bulk (+300 kcal)” goal and the “Balanced” preset tab: that is the classic macro calculator for muscle gain setup. A 200-300 calorie surplus is the sweet spot: enough to grow, small enough to stay lean.
How the math works
Step 1 – BMR (Mifflin-St Jeor, 1990): Men: 10 x weight(kg) + 6.25 x height(cm) – 5 x age + 5. Women: same, but – 161 instead of + 5. BMR is what you burn at complete rest.
Step 2 – TDEE: BMR multiplied by your activity factor (1.2 sedentary up to 1.9 extremely active) gives total daily energy expenditure.
Step 3 – Goal adjustment: a 500 kcal daily deficit for fat loss, maintenance for staying the same, or a 300-500 kcal surplus for muscle gain.
Step 4 – Macro split: the preset percentages are applied to your calorie target. Protein and carbs count 4 kcal per gram, fat counts 9 kcal per gram.
The Best Macro Split for Bulking
A balanced split works well for most lifters: roughly 25-30% protein, 40-50% carbs, and 20-30% fat. That is the default split in this bodybuilding macro calculator. Carbs are your friend when bulking — they fuel hard training and spare protein for muscle building. Keep fat moderate (around 0.5-0.8 g per kg) for hormone health. There is no need to force-feed protein beyond about 2.2 g per kg.
How Much Should You Eat to Bulk?
Start with a 200-300 calorie surplus above maintenance. That produces roughly 0.25-0.5 kg (0.5-1 lb) of weight gain per month for most lifters — mostly muscle if you train progressively. Gaining faster than that usually means excess fat. If the scale jumps more than 1% of your bodyweight per month, trim the surplus.
Clean Bulk vs Dirty Bulk
A “dirty bulk” (eating everything in sight) adds fat fast and makes the later cut miserable. A lean bulk with tracked macros builds nearly as much muscle with a fraction of the fat gain. Your TDEE tells you the maintenance baseline to add your surplus onto.
Frequently Asked Questions
How much protein do I need when bulking?
1.6 to 2.2 grams per kilogram of bodyweight per day. More than that does not build extra muscle — put the remaining calories into carbs to fuel your training.
Will I gain fat while bulking?
A little, yes — muscle and fat gain come together in a surplus. A lean bulk with a 200-300 calorie surplus keeps fat gain minimal, roughly one part fat to one part muscle or better.
How long should I bulk?
Muscle builds slowly, so commit to at least 3-6 months. Keep bulking until you have added meaningful size or your body fat creeps about 3-5% above your comfortable range, then cut.
Should I bulk or cut first?
If you are above roughly 20% body fat (men) or 30% (women), cut first. If you are already lean but small, bulk. Beginners with higher body fat can often recomp — building muscle at maintenance calories.