Protein · lean-mass insurance
Protein Calculator
The lean-mass shield in a cut. The substrate in a bulk. Tuned to your body composition and your goal.
Protein is the macronutrient that decides body recomposition
Protein is the only macronutrient your body cannot store. Every day it has to be eaten, broken down into amino acids and shuttled into muscle, organs and immune tissue. Under-eating it for even a few days in a deficit costs lean mass that the next plateau then has to reset around.
The calculator above takes weight, body fat, activity, training experience and goal so it can pick the dose the literature actually supports. With body fat measured, dosing scales to lean body mass instead of total weight: the cleaner anchor for lean and trained populations.
The result panel shows your daily target plus what it costs your body to digest, how it should be split across meals, where it lands on the protein-retention curve from the lean-physique literature, and what the same number looks like in plain food.
The protein dose across recomposition phases
The literature recommends different anchors for different phases. The calculator picks the right one and lets you compare it against the others below.
Source band: Helms et al., J Int Soc Sports Nutr 2014; Morton et al., Br J Sports Med 2018 (meta-analysis); Jäger et al., ISSN position stand 2017; Schoenfeld & Aragon, J Int Soc Sports Nutr 2018.
Four dosing rules, one calculator
Different literature anchors land at different numbers. The calculator above picks the rule that fits your goal and body composition.
LBM = lean body mass = weight × (1 − body-fat%/100). FFM (fat-free mass) is used interchangeably in the literature. Numbers above the floor still help: extra protein scales satiety, the thermic effect of food, and the margin for imperfect tracking.
The 30 grams a day you think you're eating and aren't
People who don't log overestimate protein by 30 to 50 g a day. That gap is the difference between holding lean mass and quietly losing it during a deficit.
The standard intuition is that any meal with chicken or eggs is a protein meal. The math says otherwise: a plate with 80 g of cooked chicken, two eggs and a side salad has roughly 35 g of protein, not 60. Across three meals, that miss compounds into the gap most cuts plateau on.
Garthe et al. 2011 split trained athletes into a slow-cut and a fast-cut arm with identical protein intake. The slow arm gained 2.1 percent lean mass during the cut; the fast arm lost. The single variable both arms held high was protein per kg of lean mass, day in, day out.
The fix is structural. Pick a fixed dose for breakfast, lunch and dinner, audit one week of meals against the daily total, and the gap closes inside two weeks. Per Helms 2014, the floor for lean retention in a cut sits at 1.6 g per kg of fat-free mass.
Protein and recomposition, explained
Six questions people search once protein stops being a number and starts being a tracked input.