How much protein per kg of body weight depends on what the number is for: the RDA of 0.8 g/kg is the adult minimum for the general population,1 while people who train are usually set somewhere between 1.2 and 2.4 g/kg. MacroDiet turns that range into four tiers, adds a bump on a deficit, and caps the result so it cannot crowd out the other macros.
This article gives the numbers, where each one comes from, and a worked example you can reproduce on the protein calculator.
The RDA versus the training range
The Recommended Dietary Allowance is the intake that covers the needs of nearly all healthy adults — it is a floor, not an optimum for anyone with a training goal. The Institute of Medicine sets it at 0.8 g/kg of body weight per day (56 g/day for the reference adult man, 46 g/day for the reference adult woman), inside an acceptable range of 10–35% of energy.1
The training literature works higher. The largest meta-analysis on the question pooled 49 randomised trials (1,863 participants) of resistance training lasting at least six weeks and found that adding protein increased gains in strength and fat-free mass, but that intakes above roughly 1.6 g/kg/day did not add further fat-free mass.2 Practical ranges run above that figure — up to 2.2 g/kg is common — as a margin for individual variation and for dieting, not because the pooled data showed more gain there.
In plain terms: 0.8 is enough to not be short; around 1.6 is where the measured muscle benefit levelled off in trained people; the range above it is a margin for error and for dieting.
The four tiers we use (table)
MacroDiet does not ask you to pick a number. It asks for a preference and maps it to a tier:
| Tier | g/kg (maintain or gain) | g/kg (losing goal) | 60 kg | 80 kg | 100 kg |
|---|---|---|---|---|---|
| Low | 1.2 | 1.4 | 72 / 84 g | 96 / 112 g | 120 / 140 g |
| Moderate | 1.6 | 1.8 | 96 / 108 g | 128 / 144 g | 160 / 180 g |
| High | 2.0 | 2.2 | 120 / 132 g | 160 / 176 g | 200 / 220 g |
| Extra high | 2.4 | 2.6 | 144 / 156 g | 192 / 208 g | 240 / 260 g |
The tiers are the constant PROTEIN_G_PER_KG = {1.2, 1.6, 2.0, 2.4} in the algorithm; each cell is body weight × tier, rounded to the gram. The low tier sits at the bottom of the active range, moderate at the meta-analysis breakpoint, and the top two above it.
Why more on a deficit
When the goal is set to lose, the algorithm adds 0.2 g/kg to the selected tier before it calculates grams. The reasoning is arithmetic as much as physiology: on a deficit the calorie total falls, so the same grams of protein become a larger share of a smaller budget, and the food that carries protein becomes the part of the diet the algorithm protects first. Fat has a floor and carbohydrate takes the cut — protein is the one number that goes up.
A moderate-tier 80 kg person at maintenance is set 128 g. The same person on a losing goal is set 80 × 1.8 = 144 g.
When protein gets capped
Two guardrails sit on top of the tiers.
The 50% cap. Protein calories may not exceed half of the calorie target. If grams × 4 comes to more than 0.5 × target, protein is reduced to target × 0.5 ÷ 4 grams and the calculator says so. This mostly triggers when a heavy person picks the extra-high tier on an aggressive deficit.
The 3.0 g/kg warning. If the tier plus the deficit bump ever exceeds 3.0 g/kg, the algorithm raises a warning. With the current tiers the highest reachable value is 2.6 g/kg, so the warning is a safety net for future tiers, not something a user sees today.
Worked example
A 100 kg person on a losing goal, extra-high tier, whose calorie target has come out at 1,800 kcal:
| Step | Arithmetic | Result |
|---|---|---|
| Tier + deficit bump | 2.4 + 0.2 | 2.6 g/kg |
| Raw protein | 100 × 2.6 | 260 g = 1,040 kcal |
| 50% cap | 1,800 × 0.5 | 900 kcal allowed |
| Capped protein | 900 ÷ 4 | 225 g |
The result on the protein calculator is 225 g with a "protein capped at 50% of calories" note. The same person on the moderate tier would be set 180 g (720 kcal, 40% of the target) with no cap.
In plain terms: the tier picks the grams, the deficit adds a little, and the cap stops protein from taking over a small calorie budget.
The short version
0.8 g/kg is the adult RDA — the population minimum.1 MacroDiet's tiers are 1.2 / 1.6 / 2.0 / 2.4 g/kg, plus 0.2 on a deficit; the moderate tier matches the point where a large meta-analysis found fat-free-mass gains stopped rising.2 Protein is capped at 50% of calories and flagged above 3.0 g/kg. Every figure is grams of total body weight, and the protein calculator reproduces each row of the tables above.
Educational overview only — not medical advice. Zyra is a training and nutrition tracking tool; the numbers here are the algorithm's rules and published reference values, not an individual prescription.