How your bulking calories are calculated
Bulking means eating above your TDEE (maintenance) — the extra energy, paired with progressive resistance training, is what your body uses to build new muscle. This calculator finds your TDEE first (Mifflin-St Jeor BMR × activity multiplier), then adds a lean 300 kcal surplus.
Surplus size
A 5–10% surplus (lean bulk) is the sweet spot: enough extra energy to maximize muscle growth with minimal fat gain. A 15% surplus adds scale weight faster, but a growing share of it is fat. Surpluses beyond that are "dirty bulking" — mostly fat gain for little extra muscle.
Protein and carbs
Aim for 1.6–2.2 g of protein per kg of body weight daily — more than that does not build additional muscle. Put the remaining calories toward carbohydrates, which fuel hard training sessions; the default split on this page reflects that.
Training is the stimulus
A surplus without progressive overload just adds fat. The calories are fuel — the training program is what directs them toward muscle.
Frequently asked questions
How big should my calorie surplus be?
5–10% above maintenance for a lean bulk — the range most lifters use to maximize muscle with minimal fat. 15% is aggressive; beyond that, extra calories convert mostly to fat, not muscle.
What is the difference between a lean bulk and a dirty bulk?
A lean bulk uses a small surplus (5–10%) so most gained weight is muscle. A dirty bulk uses a large, untracked surplus — the scale moves fast, but much of the gain is fat you will have to diet off later.
How much protein do I need when bulking?
1.6–2.2 g per kg of body weight per day. Eating beyond that range does not increase muscle growth — put the remaining calories toward carbs to fuel training.
How fast should I gain weight on a bulk?
A commonly recommended rate is about 0.25–0.5% of body weight per week. Faster than that and the extra is increasingly fat; much slower and you may be leaving muscle gains on the table.
Can I build muscle without a calorie surplus?
Beginners and returning lifters often can (body recomposition) at maintenance calories. Experienced lifters with low body fat gain muscle fastest in a small surplus.