Protein Intake Calculator

A protein intake calculator turns body weight, training load, and goal into a single daily gram figure for protein, the macronutrient most strongly linked to muscle protein synthesis, satiety, immune function, and lean-mass preservation during a calorie deficit. It uses the g/kg-of-bodyweight convention that has dominated sports-nutrition practice since the late 1990s, scaled by an activity × goal matrix that sits inside the International Society of Sports Nutrition's 1.6 to 2.2 g/kg/day active-adult band and leans toward the upper end of that band during fat-loss phases to protect lean mass. It is not a diet prescription and it does not replace individual assessment by a registered dietitian or sports physician, but it is a fast, evidence-grounded starting point for the vast majority of healthy adults who want to know whether their current protein intake is in the right ballpark for their goal.

The reason such a calculator matters is that protein is the macronutrient people most often get wrong, either chronically undershooting during fat-loss phases (where the deficit eats into muscle if protein is not prioritised) or chronically overshooting during maintenance phases (where surplus protein adds cost without measurable benefit). The literature now supports a relatively narrow useful range, roughly 1.6 to 2.2 g/kg/day for healthy resistance-trained adults, with diminishing returns above that, and the calculator's defaults sit firmly inside that range. The slider extends the band down to 1.2 g/kg for less-active maintainers and up to 3.0 g/kg for athletes who want to push the ceiling during aggressive cuts or hard bulks.

How to Use the Protein Intake Calculator

1. Pick your unit system, metric (kg) or imperial (lb). All calculations are performed in kilograms; imperial entries are converted to kg using the standard 0.45359237 conversion factor before the math.
2. Enter your body weight. This is the input the calculator anchors everything to.
3. Optionally tick Add lean body mass if you want a per-kg-LBM figure in the result. You can enter lean body mass directly in kg or lb, or enter a body-fat percentage from which the calculator estimates LBM as LBM = bodyweight × (1 − body-fat %).
4. Select your activity level from the five-tier scale, sedentary, light, moderate, active, athletic. The default protein multiplier auto-updates when you change this.
5. Select your goal, cut (fat loss), maintain, or bulk (muscle gain). The default multiplier also updates when you change this.
6. The g/kg slider snaps to a sensible default for your activity × goal combination. Drag it anywhere from 1.2 to 3.0 g/kg if you want to override the default for personal reasons (advanced bodybuilder, older adult, aggressive cut, etc.).
7. Select your meal split, 3, 4, or 5 meals per day, and the calculator will divide the daily total evenly.
8. Click Calculate to see your daily protein target in grams, per-meal split, optional per-kg-LBM figure, and a WHO/EFSA floor check that flags any target below 0.83 g/kg/day.

The result panel also shows the formula trace (daily protein = body weight × g/kg multiplier) so you can verify the math by hand. The default multiplier for your selected activity × goal is shown alongside your chosen slider value when they differ.

The Formula

The core formula is one line:

daily protein (g/day) = body weight (kg) × g/kg multiplier

The multiplier is a coefficient from the sports-nutrition literature that scales protein needs against bodyweight and training load. The defaults in the calculator sit inside the ISSN's 1.6 to 2.2 g/kg/day active-adult range, with the leaner end of that range reserved for moderate training loads and the heavier end for hard training or aggressive cuts. During a calorie deficit the calculator leans higher (2.0 to 2.4 g/kg) because the literature consistently shows that higher protein intake during a cut better preserves lean mass and improves body-composition outcomes.

For adults who want a safety floor rather than a performance target, the World Health Organization and the European Food Safety Authority set the Population Reference Intake at 0.83 g/kg/day for healthy adults, rising to 1.0 to 1.2 g/kg/day for older adults to counteract sarcopenia. The calculator surfaces this floor in the result panel and highlights the target in amber if it falls below 0.83 g/kg/day for your bodyweight, useful sanity check for very low-calorie diets or for older adults whose protein needs are commonly under-estimated.

For users who supplied a lean body mass, the calculator also reports a per-kg-LBM figure (daily protein / LBM kg). Lean-mass targets during a cut often run 2.3 to 3.1 g/kg LBM for trained athletes; for less-trained adults the corresponding figure is usually lower. The per-kg-LBM output is helpful if you know your body composition (DEXA, BodPod, or skinfold) and want to track protein targets as your body recomposes.

Real-World Worked Examples

Example 1, 80 kg sedentary office worker maintaining weight

Body weight 80 kg, sedentary activity level, maintenance goal. Default multiplier for this combination is 1.6 g/kg.

80 × 1.6 = 128 g of protein per day

This is well above the WHO/EFSA floor (66.4 g/day for 80 kg) and inside the ISSN active-adult band. For a 50-year-old office worker who does no structured training, this is a comfortable maintenance target that supports normal immune function and lean-mass turnover. Split across four meals that is 32 g per meal, easily reachable on a normal mixed diet (a chicken breast at dinner plus yoghurt at breakfast plus a protein shake at lunch covers most of it).

Example 2, 80 kg recreational lifter in a 500 kcal/day deficit (active, cut)

Same body weight as Example 1 but now the lifter is training 4 to 5 days a week and in a moderate cut. Activity becomes "active", goal becomes "cut", default multiplier rises to 2.2 g/kg.

80 × 2.2 = 176 g of protein per day

That is roughly 0.88 g per pound of bodyweight, a number commonly cited in the hypertrophy literature for recreational lifters in a deficit. Split across four meals, it works out to 44 g per meal, which is on the higher side but well within the per-meal muscle protein synthesis stimulation threshold of roughly 0.4 g/kg/meal identified by Schoenfeld and Aragon. Morton et al. (2018) found diminishing hypertrophy returns above about 1.6 g/kg in resistance-trained adults, but the extra protein during a cut is not wasted, it improves satiety, reduces lean-mass loss, and protects training performance in a deficit.

Example 3, 70 kg sedentary adult trying to lose fat fast (sedentary, cut)

A 70 kg sedentary adult who has decided to cut hard. Activity is sedentary, goal is cut, default multiplier is 2.0 g/kg.

70 × 2.0 = 140 g of protein per day

Even for a sedentary adult in a cut, the calculator recommends pushing protein toward the upper end of the supported range, because the literature shows that higher protein in a deficit better preserves lean mass, and sedentary adults in particular tend to lose lean mass faster than active adults when calories drop, because they are not sending the muscle protein synthesis signal that comes from resistance training. 140 g/day spread across four meals is 35 g per meal, a manageable target on a normal diet.

Example 4, 90 kg athletic lifter in a lean bulk

A 90 kg competitive powerlifter running a small caloric surplus. Activity is athletic, goal is bulk, default multiplier is 2.4 g/kg.

90 × 2.4 = 216 g of protein per day

That is 2.4 g/kg, which is at the top of the supported range but well within what a large athlete can comfortably consume. Split across five meals, it works out to about 43 g per meal, which keeps each meal comfortably inside the muscle protein synthesis response window. Helms et al. (2014) and the ISSN position stand both support targets up to ~2.5 to 2.7 g/kg for natural lifters in a bulk.

Example 5, 75 kg moderate gym-goer in a bulk (moderate, bulk)

Body weight 75 kg, training 3 days a week, in a small surplus. Default multiplier 1.8 g/kg.

75 × 1.8 = 135 g of protein per day

This is a textbook hypertrophy target for a moderate gym-goer. It sits inside the ISSN active-adult range and represents the dose most likely to deliver the bulk of the muscle-building signal without overshooting on cost or satiety. Three meals per day works out to 45 g per meal; four meals works out to about 34 g per meal. Both are well-tolerated.

Common Mistakes When Using a Protein Intake Calculator

Mistake 1: Treating the result as a precise prescription. The g/kg-of-bodyweight convention is a population-level estimate. Individual protein needs vary with age, training history, lean mass, gut microbiome, sleep, and stress. Use the calculator's output as a starting point, then adjust based on body-composition response over 4 to 8 weeks.

Mistake 2: Ignoring the WHO/EFSA floor. If your target is below 0.83 g/kg/day for an extended period, you risk lean-mass loss, immune compromise, and impaired recovery from training. The calculator flags this in the result panel, pay attention to it, especially during aggressive cuts or in older adults.

Mistake 3: Confusing per-kg-bodyweight with per-kg-lean-mass. A 100 kg adult at 30% body fat has 70 kg of lean mass. 1.6 g/kg of bodyweight gives 160 g/day; 2.3 g/kg of LBM gives 161 g/day. The two metrics agree at that point but diverge as body composition changes. If you know your LBM, prefer the per-kg-LBM metric during cuts.

Mistake 4: Going above 2.2 g/kg without a reason. The literature does not show meaningful additional hypertrophy benefit from protein above ~2.2 g/kg/day in trained adults (Morton et al., 2018). Pushing higher wastes food budget, can crowd out other macronutrients, and is unnecessary outside specific scenarios (very aggressive cuts, large athletes who cannot get enough protein in 3 to 4 meals).

Mistake 5: Loading all protein into one meal. Per-meal muscle protein synthesis has a ceiling at roughly 0.4 to 0.5 g/kg/meal for most adults. Eating 200 g of protein in one sitting does not produce 200 g of MPS stimulation, the excess is oxidised. Split the daily total across 3 to 5 meals for better utilisation.

What the Calculator Does and Does Not Tell You

The calculator tells you the daily gram target that best matches the literature for your bodyweight, training load, and goal. It also tells you the per-meal split for 3, 4, or 5 meals, and optionally a per-kg-LBM figure if lean mass was supplied. It does not tell you:

• Where the protein should come from (food first; supplements optional)
• How much total energy you need (use a separate TDEE / calorie calculator)
• How the protein should be distributed across specific foods (a meal planner is a separate question)
• Whether you have a medical condition that changes protein needs (kidney disease, liver disease, certain metabolic disorders)

For a healthy adult without contraindications, the calculator's output is a reliable starting point. For someone with a relevant medical condition, consult a clinician before substantially changing protein intake.

Frequently Asked Questions

How much protein do I need per day to build muscle? For most healthy adults in a small surplus, the ISSN-cited active-adult range of 1.6 to 2.2 g/kg/day covers the bulk of muscle-building response. Aim for the middle of the band (1.8 g/kg) and adjust based on 4 to 8 week body-composition response. There is no consistent evidence that going above 2.2 g/kg produces more muscle in trained adults, so the calculator's default for moderate-to-active bulks sits at 1.6 to 2.0 g/kg, not higher.

How much protein do I need to lose fat without losing muscle? During a calorie deficit, push protein toward the upper end of the supported range, 2.0 to 2.4 g/kg/day for most adults, or 2.3 to 3.1 g/kg of lean body mass if you know your LBM. Higher protein during a cut improves satiety, protects strength, and reduces lean-mass loss. The calculator's "cut" presets sit at 2.0 to 2.4 g/kg exactly for this reason.

Is the WHO/EFSA 0.83 g/kg/day enough for me? For a sedentary adult in energy balance with no specific muscle or performance goal, 0.83 g/kg/day is sufficient to maintain nitrogen balance and basic immune function. For anyone training, cutting, bulking, recovering from injury, or over 65, target the upper end of the supported range, the WHO/EFSA figure is a population minimum, not a performance target.

What is the best protein per-kg-of-lean-mass target during a cut? For trained athletes in an aggressive cut, 2.3 to 3.1 g/kg of lean mass is a common target supported by Helms et al. (2014) and the ISSN position stand. For less-trained adults, the corresponding per-LBM target is usually a bit lower. The calculator reports this figure automatically if you tick "Add lean body mass" and supply either an LBM number or a body-fat percentage.

Should older adults (65+) eat more protein? Yes. EFSA recommends 1.0 to 1.2 g/kg/day minimum for older adults, and the sarcopenia literature suggests 1.2 to 1.6 g/kg/day is more protective than the general adult PRI. Older muscles are also less sensitive to per-meal protein doses (anabolic resistance), so per-meal targets of 35 to 40 g are often recommended over a smaller number of large meals.

Can I eat too much protein in one meal? Per-meal muscle protein synthesis has a ceiling at roughly 0.4 to 0.5 g/kg/meal for most adults. Eating far above that does not produce proportionally more MPS, the excess is oxidised for energy. The calculator's meal split (3, 4, or 5 meals) keeps per-meal protein at or below this ceiling when the daily target is inside the supported range.

Is high protein bad for your kidneys? For healthy adults without pre-existing kidney disease, current evidence does not show kidney damage from protein intakes up to 2.5 g/kg/day. The concern applies to people with chronic kidney disease or other renal conditions, who should consult a clinician. Hydration matters at very high intakes, drink enough water.

Does protein timing matter? Total daily protein matters more than exact timing. That said, distributing protein across 3 to 5 meals (rather than loading it into one meal) modestly improves 24-hour muscle protein synthesis. Post-workout, the "anabolic window" is wider than the old 30-minute myth, meals within a couple of hours of training support recovery well.

Do I need protein supplements like whey, casein, or plant blends? No. Whole foods cover protein needs for most people. Whey is convenient, fast-absorbing, and inexpensive per gram of protein, useful as a meal-replacement or post-workout top-up. Casein is slow-digesting and useful before bed. Plant blends (pea + rice) cover the amino-acid profile adequately for most adults, though slightly higher total intake may be needed due to lower digestibility.

What happens if I eat less protein than the calculator recommends? Short-term, nothing dramatic, the body draws on amino acid pools to maintain essential functions. Long-term, undershooting protein during a cut accelerates muscle loss, impairs immune function, slows wound healing, and reduces training recovery. The calculator's WHO/EFSA floor flag is a useful alert for sustained undershooting.

Also try these free tools:

• Protein Calculator, simpler protein target for weight and goals.
• Calorie Calculator, daily energy needs.
• Macro Calculator, split between protein, carbs, and fat.
• Body Fat Calculator, body composition estimate.
• TDEE Calculator, total daily energy expenditure.