How the bulking numbers are set
The calculator finds your maintenance calories with the Mifflin-St Jeor equation and your activity level, then adds a 10% surplus. For most people that is 200 to 300 calories a day, which is enough to build muscle without the fat gain that comes with a dirty bulk.
Protein is set at about 1.8 g per kg of bodyweight. Above that, more protein does not build more muscle in a surplus, so the extra calories go to carbs, which fuel training, and fat.
How fast should you gain?
Aim for about 0.25 to 0.5% of bodyweight a week if you are new to lifting, and the lower end once you have trained for a few years. Faster gain is mostly fat. Weigh yourself most mornings and watch the weekly average, not single days.
When a bulk is not the right call
If you are carrying a fair amount of fat, building muscle at maintenance or in a small deficit (a recomp) often looks better sooner than a bulk. A physique scan is a quick way to tell: if leanness is the score holding you back, cut first.
Want to see what your current physique looks like as a number? Try the freeAI physique analyzer, or use the fullmacro calculator to compare diet styles.
Common questions
- How many calories should I eat to bulk?
- About 10% above your maintenance calories, which is 200 to 300 extra calories a day for most people. Use the calculator for your own number.
- How much protein do I need to build muscle?
- About 1.6 to 2.2 g per kg of bodyweight a day. The calculator uses 1.8 g per kg in a surplus, where extra protein adds little.
- How much weight should I gain per month?
- Roughly 1 to 2% of bodyweight a month as a beginner and under 1% for experienced lifters. Faster than that is mostly fat.
- What is the difference between a lean bulk and a dirty bulk?
- A lean bulk uses a small surplus so most of the gain is muscle. A dirty bulk eats far above maintenance and gains faster, but much of it is fat you later have to cut.
- Should I bulk or cut first?
- If you are lean enough to see some ab outline, bulk. If not, cut or recomp first. Muscle shows best, and a bulk feels best, from a lean starting point.