Protein Calculator

A protein calculator turns your body data into one usable number: how many grams of protein to eat per day. Protein does the heavy lifting among the macronutrients — it repairs muscle and tissue after training, carries enzymes and hormones, supports your immune system, and keeps you full on relatively few calories. Under-eating it slows recovery, erodes muscle on a diet, and makes every meal less satisfying; over-estimating it just wastes plate space.

The protein you eat is built from 20 amino acids, nine of which your body cannot make and must come from food. That is why total daily grams matter more than any single superfood: hit your number across the day and your body has the raw materials it needs.

This calculator is built for people training or dieting — including on intermittent fasting schedules — and it goes one step further than a single number: it gives you a science-based range for your goal and splits the target across 2, 3, or 4 meals so it fits inside your eating window.

Daily protein is calculated from body weight, not from calories: multiply your weight in kilograms by an evidence-based factor for your goal and activity level.

Formula: Daily Protein (g) = Body Weight (kg) × Factor (g/kg)

Worked Example

A 75 kg (165 lb) person training 3-5 days a week who wants to build muscle lands near the middle-upper part of the 1.6-2.2 band at 1.9 g/kg: 75 × 1.9 ≈ 143 g of protein per day, with the full range spanning 120-165 g. The same person dieting instead would use 1.4 g/kg → 105 g per day.

The calculator runs this automatically and picks your point inside the range from how active you are — sedentary users sit near the bottom of the band, hard trainers near the top.

The official recommended dietary allowance (RDA) is 0.8 g per kg — the intake that prevents deficiency in almost all healthy adults. It is a floor, not a target: studies in resistance-trained and dieting populations consistently show better outcomes well above it. Three evidence-backed lanes cover most people:

• Fat loss (1.2-1.6 g/kg): higher protein improves satiety and protects lean mass, so more of the weight you lose is fat — especially important inside a calorie deficit.
• Maintenance (1.2-2.0 g/kg): sedentary weeks sit near the bottom; regular training pushes you up the band for recovery and performance.
• Muscle gain (1.6-2.2 g/kg): meta-analyses show growth maxes out around 1.6 g/kg, with hard trainers and older adults often choosing the upper half.

Older adults deserve a special note: after 60, muscle becomes harder to hold onto, and intakes near 1.2-1.6 g/kg help defend against age-related muscle loss — well above the RDA.

Not sure which lane you are in? Pair this tool with the Maintenance Calorie Calculator or the Calorie Deficit Calculator — protein decides what your weight change is made of, while calories decide its direction.

Fasting changes when you eat your protein, not how much. The catch is compression: a 142 g target inside an 8-hour window cannot happen by accident — it needs two or three protein-anchored meals of 40-50 g each.

Structure it around the fast break. Open your window with 30-45 g — eggs and Greek yogurt at breakfast, or chicken, fish, tofu, or a shake wherever your window opens — because that first meal does the most work for recovery after your fast. Place your second anchor at the final meal before the window closes so overnight muscle breakdown has less raw material shortage to work with. Cover a large gap between the two with a 15-20 g snack: cottage cheese, jerky, edamame, or a shake.

Worried the window is too short? Research is reassuring: the "20-30 g limit per meal" idea is a myth, and total daily intake is what drives results. Use the per-meal table in your result above to match the split to your schedule, and plan the window itself with the Intermittent Fasting Calculator.

Hitting your target is easier when most meals are built around concentrated sources. Approximate protein per 100 g (cooked, per USDA FoodData Central):

Animal and plant proteins both count — what matters is the daily total and variety. If meals fall short, a protein shake is a convenient top-up, not a requirement.

For healthy adults, the evidence puts the comfortable ceiling well above most targets: intakes up to roughly 2.0-2.2 g per kg show no harmful effects on kidney, liver, or bone health in studies of trained people, and problems become plausible only past 3-4 g/kg sustained for long periods. Since this calculator's highest possible point is 2.2 g/kg, a healthy user cannot dial it into a risky range.

Two real caveats remain. People with existing kidney disease should set protein targets with their clinician, because damaged kidneys handle protein differently. And pushing protein far past your target simply displaces carbohydrates, fiber, and micronutrients your performance still needs — hit your number, then move on with your day.

Targets are computed as body weight × grams-per-kilogram, with ranges anchored to published research: the RDA of 0.8 g/kg from the NIH Office of Dietary Supplements, 1.4-2.0 g/kg for active adults from the ISSN position stand on protein and exercise, and 1.6-2.2 g/kg for muscle gain consistent with the Morton et al. 2018 meta-analysis in the British Journal of Sports Medicine. Your chosen activity level moves your target between the bottom and top of your goal's range.

Treat the result as a planning estimate: protein needs also shift with total calories, training type, age, and health status, and targets are based on total body weight rather than lean mass (very high body-fat percentages may justify slightly lower figures). The per-meal split is guidance, not a rule — the daily total is what counts.

This tool provides planning estimates only and is not medical advice. If you are pregnant, breastfeeding, managing kidney or other medical conditions, or have a history of disordered eating, work with a qualified professional instead of self-prescribing targets.

Last updated: November 2026. Ranges follow the NIH ODS protein fact sheet, the ISSN position stand (2017), and Morton et al. (2018).