Lean Bulk Calculator
A lean bulk means running a small, controlled calorie surplus so you add muscle while keeping fat gain to a minimum. Enter your maintenance calories (TDEE) — or let the tool estimate them — pick a tight surplus, and you'll get your target calories, the weekly gain rate, and a protein/fat/carb split tuned for lean gaining.
Your lean-bulk targets
Eat about:
Suggested macros
Protein is set at ~1 g per pound of body weight to maximise muscle retention, fat at ~25% of total calories, and the remaining calories come from carbohydrates to fuel training.
What a lean bulk actually is
A lean bulk — sometimes called a clean bulk — is the deliberate practice of gaining weight slowly, in a small calorie surplus, so that as much of the new weight as possible is muscle rather than fat. The logic is simple: your body can only build muscle at a capped rate. Eat far above that rate and the extra calories have nowhere to go but fat stores. Eat just slightly above maintenance, train hard, and you give muscle the energy it needs while leaving little spare for fat gain.
How big should a lean-bulk surplus be?
One pound of body weight stores roughly 3,500 calories. A surplus of about 300 kcal per day therefore adds up to ~2,100 kcal over a week — about 0.6 lb of gain, mostly tunable down toward 0.3 lb/week of "real" tissue once water settles. That is why this calculator caps the surplus tightly at +200 to +400 kcal. Beginners and people returning from a layoff can build muscle quickly and may use the higher end; intermediate and advanced lifters, whose muscle-building rate is slower, are usually better served by the +200 end so they do not out-eat the muscle they can actually build.
A worked example
Say your maintenance is 2,500 kcal, you choose the +300 kcal lean surplus, and you weigh 160 lb. Your target is 2,500 + 300 = 2,800 kcal/day. The weekly rate is 300 × 7 ÷ 3,500 = 0.6 lb/week. For macros: protein at 1 g/lb is 160 g (640 kcal); fat at 25% of 2,800 is 700 kcal = 78 g; the remaining 2,800 − 640 − 700 = 1,460 kcal come from carbs = 365 g. That is a textbook lean-bulk day: high protein to build, ample carbs to train, and just enough of a surplus to grow without spilling into fat.
Sources: Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990 (PubMed) · Academy of Nutrition and Dietetics · NIH / NIDDK Weight Management · Examine.com — Protein intake.
Frequently asked questions
- What surplus is best for a lean bulk?
- A small surplus of roughly 200-400 calories above maintenance per day. That keeps the weekly gain around 0.2-0.4 lb so most of the new weight is muscle. Beginners can use the higher end; experienced lifters should stay near +200.
- How fast should I gain on a lean bulk?
- About 0.25-0.5 lb per week, or roughly 2-4 lb per month, is a realistic lean-bulk pace. Gaining much faster than that means a growing share of the weight is body fat, since muscle is built at a capped rate.
- How much protein do I need on a lean bulk?
- About 1 gram of protein per pound of body weight (roughly 1.6-2.2 g/kg) is well supported by research for muscle gain. This calculator sets protein at 1 g/lb and fills the rest of your calories with fat and carbohydrates.
- Lean bulk or dirty bulk — which is better?
- For nearly everyone, a lean bulk wins. A dirty bulk (large, uncontrolled surplus) gains weight faster but a much larger fraction is fat, which then has to be dieted off. A lean bulk keeps you leaner year-round and shortens any future cut.
- Why is my real weight change different from the estimate?
- Predictive equations carry about a 10% error and daily weight swings with water, glycogen, and food in transit. Judge a lean bulk by the weekly average over 2-3 weeks, not day-to-day, and adjust the surplus by 100 kcal if needed.