What Is Protein?
Protein is one of the three macronutrients, alongside carbohydrate and fat. Structurally it is a chain of amino acids, and the reason you have to eat it is that the chains in your food are taken apart during digestion and reassembled into the ones your body needs — muscle fiber, collagen, digestive enzymes, transport proteins, antibodies.
MedlinePlus, the consumer service of the U.S. National Library of Medicine, sorts amino acids into three classes. Essential amino acids cannot be manufactured in the body at all and must arrive in food. Nonessential ones the body makes for itself, either from essential amino acids or from the normal turnover of its own proteins. Conditional amino acids are usually nonessential but become required during illness and stress, when demand outruns what the body can produce.
One line from that same source contradicts a widespread piece of gym advice: essential amino acids do not have to be eaten at every meal, and balance across the whole day matters more. That is permission to distribute the total this calculator gives you around the schedule you actually have, rather than forcing four identical portions into a day that will not hold them.
Complete and Incomplete Protein Sources
Animal foods — meat, fish, eggs, milk — deliver every essential amino acid in one package. Plant foods supply them too, but in different proportions, so a diet built on a single plant staple can run short on one amino acid while the total grams look healthy. MedlinePlus states plainly that you do not need to eat animal products to get all the protein you need, listing soy, beans, legumes, nut butters, wheat germ and quinoa among the sources.
The Diet Type selector on this page does not act on any of that. Selecting Omnivore, Vegetarian or Vegan returns exactly the same number of grams, because the calculator answers a question about quantity and stops there. Which foods reach that quantity, and how many amino acids ride along with them, is a separate decision the tool does not make for you.
Protein Measured Against a Calorie Budget
One gram of protein supplies 4 calories. That conversion is what ties a protein target to everything else you eat: the 107.8 g figure above is 431 calories, which on a 2,000-calorie day is 22 percent of intake.
MedlinePlus puts the recommended range for adults at 10 to 35 percent of total calories — the Acceptable Macronutrient Distribution Range from the 2005 Dietary Reference Intakes. For the 70 kg body used throughout this page, all nine settings sit inside it on a 2,000-calorie day, from 56.0 g at 11 percent to 159.6 g at 32 percent. The range is a share rather than a gram figure, though, so two things move you out of it: a smaller calorie total, since those same 159.6 g cross 35 percent on any day under 1,824 calories, and a heavier body, since 110 kg on Build Muscle and Active returns 250.8 g — 50 percent of 2,000 calories.
To see those grams sitting beside carbohydrate and fat inside a single calorie total, run the Macro Calculator.
How Do You Calculate Protein Intake?
Two multiplications, in this order: body weight times a goal factor, then times an activity factor. Nothing else on the form enters the equation.
Daily protein (g) = weight (kg) × goal factor × activity factor
The Protein Formula, Written Out
The Fitness Goal control does not merely label a row. Its stored value is the number that multiplies — selecting Weight Loss passes 1.4 straight into the equation.
Goal factor: Maintain Weight = 0.8 Weight Loss = 1.4 Build Muscle = 1.9
Activity factor: Sedentary = 1.00 Moderate = 1.10 Active = 1.20
Daily protein (g) = weight (kg) × goal factor × activity factor
The answer is rounded to one decimal place at the very end and nothing is rounded on the way, so a figure quoted anywhere on this page and the figure on your screen agree exactly. The whole calculation runs in your browser, on a single formula module the page loads when you press Calculate.
The 0.8 baseline is the adult Recommended Dietary Allowance from the 2005 Dietary Reference Intakes — the intake that meets the requirement of nearly all healthy, sedentary adults. It is a floor for preventing deficiency, not a performance target, and that distinction is the reason the other two factors exist.
What the Two Multipliers Actually Come To
Grams shown for a 70 kg body weight.
Multiply the goal factor by the activity factor and you get the effective grams per kilogram the calculator is really using. These nine combinations are every answer the tool can return for one body weight.
| Goal setting | Sedentary (×1.00) | Moderate (×1.10) | Active (×1.20) |
|---|---|---|---|
| Maintain Weight (0.8) | 0.80 g/kg — 56.0 g | 0.88 g/kg — 61.6 g | 0.96 g/kg — 67.2 g |
| Weight Loss (1.4) | 1.40 g/kg — 98.0 g | 1.54 g/kg — 107.8 g | 1.68 g/kg — 117.6 g |
| Build Muscle (1.9) | 1.90 g/kg — 133.0 g | 2.09 g/kg — 146.3 g | 2.28 g/kg — 159.6 g |
Four of those nine effective factors land inside the 1.4 to 2.0 g/kg band that the International Society of Sports Nutrition recommends for exercising adults. The three maintenance settings sit below it on purpose, tracking the 0.8 g/kg reference intake. Two sit above it — 2.09 and 2.28 g/kg, both on Build Muscle.
That top-right cell is the one place the calculator is more generous than the position stand it draws on. If you pick Build Muscle and Active and the number looks large, this is why: you have stacked the highest goal factor on the highest activity uplift, and 2.28 g/kg is past the 2.0 ceiling in that document.
Step by Step
The form asks six questions. Three of them reach the arithmetic.
- Enter your weight in kilograms. If your scale reads pounds, divide by 2.20462 first — the field performs no conversion.
- Enter your age in years. It is recorded on the form and does not change the result.
- Choose Male, Female or Other. Also recorded, also without effect on the grams.
- Choose an activity level: Sedentary, Moderate (light exercise 1-3 days a week) or Active (hard exercise 4-6 days a week). This multiplies the result by 1.00, 1.10 or 1.20.
- Choose a fitness goal: Maintain Weight, Weight Loss or Build Muscle. This supplies the 0.8, 1.4 or 1.9 factor and is the largest lever on the page.
- Choose a diet type: Omnivore, Vegetarian or Vegan. Recorded, and identical in every case.
All four selectors are button groups rather than dropdown lists, and each arrives pre-selected on its first option, so Activity Level opens on Sedentary and Fitness Goal on Maintain Weight. A control you skip still contributes a factor — it contributes 1.00 and 0.8, which is the sedentary reference intake rather than a blank.
The output is one figure in grams per day. There is no meal plan attached, no calorie total, and no macro split — those live on separate tools, and the grams here have to be fitted into them by hand.
Protein Example: 70 kg Losing Weight on Moderate Exercise
Weight 70 kg, goal Weight Loss, activity Moderate — light exercise one to three days a week.
Daily protein = 70 × 1.4 × 1.10
Daily protein = 98.0 × 1.10 = 107.8 g/day
- Daily protein target
- 107.8 g/day
That is 431 calories from protein and, split across four eating occasions, roughly 27 g each. Hold the goal and move only the activity selector: 98.0 g at Sedentary, 117.6 g at Active — a spread of 19.6 g across the entire field.
Read against the research, 107.8 g is 1.54 g per kilogram. The 2018 meta-analysis by Morton and colleagues found that the benefit of additional protein for resistance-training gains flattened out at roughly 1.6 g/kg/day, which for this person would be 112.0 g. So the Moderate setting lands 4.2 g short of that breakpoint and the Active setting clears it by 5.6 g.
Protein Example: 85 kg Building Muscle on Hard Training
Weight 85 kg, goal Build Muscle, activity Active — hard exercise four to six days a week.
Daily protein = 85 × 1.9 × 1.20
Daily protein = 161.5 × 1.20 = 193.8 g/day
- Daily protein target
- 193.8 g/day
193.8 g is 775 calories: 31 percent of a 2,500-calorie day, 26 percent of a 3,000-calorie one. Divided across three meals it is 64.6 g each, a portion size most people have to plan deliberately rather than reach by accident.
This is the calculator working at its ceiling, 2.28 g per kilogram. Dropping the activity selector one notch to Moderate gives 177.7 g; Sedentary gives 161.5 g. A 32.3 g swing sits inside a field about how many days a week you train, so it is worth answering that field from your last month rather than your best week.
If Your Scale Reads Pounds
The weight field is labeled kg and there is no unit selector beside it. Typing a pound figure into it does not convert — the equation treats the number as kilograms, and the target comes out about 2.2 times too high.
kilograms = pounds ÷ 2.20462
Someone weighing 154 lb is 69.9 kg. Entered as 70 on Build Muscle and Active the result is 159.6 g. Entered as 154, it is 351.1 g — not merely wrong but physically unreachable, which at least makes the mistake easy to spot.
Conversions worth having: 120 lb = 54.4 kg, 150 lb = 68.0 kg, 180 lb = 81.6 kg, 200 lb = 90.7 kg, 250 lb = 113.4 kg.
Protein Chart: Daily Grams by Body Weight
Every figure in these tables comes out of the calculator itself. The first is the Sedentary column, which is the goal factor alone with no activity uplift applied — find your weight, read across to your goal.
| Body weight | Maintain Weight (0.8) | Weight Loss (1.4) | Build Muscle (1.9) |
|---|---|---|---|
| 50 kg (110 lb) | 40.0 g | 70.0 g | 95.0 g |
| 55 kg (121 lb) | 44.0 g | 77.0 g | 104.5 g |
| 60 kg (132 lb) | 48.0 g | 84.0 g | 114.0 g |
| 65 kg (143 lb) | 52.0 g | 91.0 g | 123.5 g |
| 70 kg (154 lb) | 56.0 g | 98.0 g | 133.0 g |
| 75 kg (165 lb) | 60.0 g | 105.0 g | 142.5 g |
| 80 kg (176 lb) | 64.0 g | 112.0 g | 152.0 g |
| 85 kg (187 lb) | 68.0 g | 119.0 g | 161.5 g |
| 90 kg (198 lb) | 72.0 g | 126.0 g | 171.0 g |
| 95 kg (209 lb) | 76.0 g | 133.0 g | 180.5 g |
| 100 kg (220 lb) | 80.0 g | 140.0 g | 190.0 g |
| 110 kg (243 lb) | 88.0 g | 154.0 g | 209.0 g |
Two rows are worth noticing side by side. A 95 kg person on Weight Loss is told 133.0 g, and so is a 70 kg person on Build Muscle. Identical targets, entirely different reasons — which is a reminder that the number alone carries no information about why it was produced.
Protein Chart at the Moderate Setting
Light exercise one to three days a week multiplies every figure above by 1.10.
| Body weight | Maintain Weight | Weight Loss | Build Muscle |
|---|---|---|---|
| 50 kg | 44.0 g | 77.0 g | 104.5 g |
| 60 kg | 52.8 g | 92.4 g | 125.4 g |
| 70 kg | 61.6 g | 107.8 g | 146.3 g |
| 80 kg | 70.4 g | 123.2 g | 167.2 g |
| 90 kg | 79.2 g | 138.6 g | 188.1 g |
| 100 kg | 88.0 g | 154.0 g | 209.0 g |
Protein Chart at the Active Setting
Hard exercise four to six days a week multiplies the sedentary figures by 1.20.
| Body weight | Maintain Weight | Weight Loss | Build Muscle |
|---|---|---|---|
| 50 kg | 48.0 g | 84.0 g | 114.0 g |
| 60 kg | 57.6 g | 100.8 g | 136.8 g |
| 70 kg | 67.2 g | 117.6 g | 159.6 g |
| 80 kg | 76.8 g | 134.4 g | 182.4 g |
| 90 kg | 86.4 g | 151.2 g | 205.2 g |
| 100 kg | 96.0 g | 168.0 g | 228.0 g |
The uplift is proportional, so it grows with body size. At 50 kg the Active setting adds 8.0 g to a maintenance target; at 100 kg it adds 16.0 g. The same 20 percent buys twice the grams because it is 20 percent of twice the base.
What Those Grams Cost in Calories
At 4 calories per gram, a protein target is also a claim on your calorie budget. These are the 70 kg results converted.
| Setting (70 kg) | Grams per day | Calories from protein | Share of a 2,000 kcal day |
|---|---|---|---|
| Maintain, sedentary | 56.0 g | 224 kcal | 11% |
| Maintain, active | 67.2 g | 269 kcal | 13% |
| Weight loss, moderate | 107.8 g | 431 kcal | 22% |
| Weight loss, active | 117.6 g | 470 kcal | 24% |
| Build muscle, sedentary | 133.0 g | 532 kcal | 27% |
| Build muscle, active | 159.6 g | 638 kcal | 32% |
Every row here stays inside the 10 to 35 percent range for adults. It is still worth checking against your own calorie total rather than this one, because a heavy person on the Build Muscle setting who is also eating a small daily total can leave that range without anything on screen flagging it.
For the calorie total those grams have to fit inside, work out your maintenance burn with the TDEE Calculator.
What Those Grams Look Like as Food
Protein density varies far more between foods than most people assume. These are per-100-gram values from USDA FoodData Central's SR Legacy dataset, with a realistic portion worked out beside each.
| Food | Protein per 100 g | Portion | Protein in that portion |
|---|---|---|---|
| Chicken breast, roasted, skinless | 31.0 g | 100 g | 31.0 g |
| Salmon, Atlantic farmed, cooked | 22.1 g | 100 g | 22.1 g |
| Greek yogurt, plain nonfat | 10.2 g | 170 g pot | 17.3 g |
| Cottage cheese, 2% lowfat | 10.4 g | 150 g | 15.6 g |
| Lentils, boiled | 9.0 g | 198 g (1 cup, cooked) | 17.9 g |
| Tofu, raw firm, calcium sulfate set | 17.3 g | 100 g | 17.3 g |
| Egg, whole, hard-boiled | 12.6 g | 50 g (1 large) | 6.3 g |
| Milk, 2% reduced fat | 3.3 g | 240 g glass | 7.9 g |
Set that against a 107.8 g target and the practical gap opens up: chicken breast covers it in about three and a half 100 g portions, firm tofu in just over six, and 2% milk would take more than thirty. The Diet Type selector will not do this arithmetic for you, which is exactly why it is worth doing once by hand before committing to a target.
How to Read Your Protein Result
The figure is a daily total. It is not a per-meal instruction, not a threshold you fail by missing, and not a limit you breach by exceeding. Three questions turn it into something usable: is it plausible for a body like yours, does it fit inside your calories, and can you realistically eat it.
Where Your Number Sits Against the Published Ranges
Four published intakes bracket almost every result this tool can produce. The grams column uses the same 70 kg reference body as the rest of the page.
| Published intake | Grams per day at 70 kg | Where this tool's settings land |
|---|---|---|
| 0.8 g/kg — adult RDA, 2005 Dietary Reference Intakes | 56 g | Maintain + Sedentary (56.0 g) |
| 1.0-1.2 g/kg — PROT-AGE, healthy older adults | 70-84 g | Nothing lands inside it — maintenance tops out at 67.2 g, and the next setting up overshoots to 98.0 g |
| 1.4-2.0 g/kg — ISSN position stand, exercising adults | 98-140 g | All three Weight Loss settings (98.0-117.6 g) and Build Muscle + Sedentary (133.0 g) |
| ~1.6 g/kg — Morton meta-analysis breakpoint for training gains | 112 g | Weight Loss + Active (117.6 g) and everything above it |
None of those figures is a maximum. The International Society of Sports Nutrition's 2017 position stand reviewed intakes well above the RDA in healthy, exercising people and did not find evidence of harm to kidney or liver function in that population — worth knowing, because it is simultaneously the most repeated concern about protein and the least supported one for the people most likely to be reading this page. It says nothing about people who already have kidney disease, which the limits section takes up.
If your result falls below every band in the table, you have almost certainly selected Maintain Weight while training. The maintenance factor tracks a sedentary reference intake, and no amount of activity uplift lifts 0.8 g/kg into the exercising range: the highest it goes is 0.96 g/kg.
Splitting the Total Across the Day
Divide by the number of eating occasions you actually have, not the number you plan to have. These are the four worked results from this page, split three ways.
| Daily target | Across 3 meals | Across 4 | Across 5 |
|---|---|---|---|
| 95.5 g — 62 kg, weight loss, moderate | 31.8 g | 23.9 g | 19.1 g |
| 107.8 g — 70 kg, weight loss, moderate | 35.9 g | 26.9 g | 21.6 g |
| 159.6 g — 70 kg, build muscle, active | 53.2 g | 39.9 g | 31.9 g |
| 193.8 g — 85 kg, build muscle, active | 64.6 g | 48.5 g | 38.8 g |
Since MedlinePlus notes that essential amino acids do not need to appear at every meal, and that balance over the day is what counts, an uneven split is not a failure. The reason to spread it anyway is logistical rather than biochemical: 64.6 g in a single sitting is a serious plate of food, and three of those is a harder day to execute than five smaller ones.
Use the per-meal figure as the number you actually carry around. Daily totals are hard to track in your head; a target of roughly 27 g at each of four meals is a decision you can make at the counter.
When the Result Looks Wrong
Two things account for nearly every implausibly high answer. A pound figure typed into a kilogram field multiplies everything by about 2.2. And the Active option chosen on ambition rather than history adds 20 percent — it means hard exercise four to six days a week already completed, not an intention to start.
Answers that look too low almost always come from a control nobody touched. Fitness Goal opens on Maintain Weight and Activity Level on Sedentary, so entering a weight and pressing Calculate without changing anything else returns the 0.8 g/kg reference intake — 56.0 g at 70 kg — no matter how hard you train.
The magnitudes are worth memorizing in both directions. At 70 kg on Build Muscle, moving from Sedentary to Active adds 26.6 g. At the same weight on moderate activity, moving the goal from Maintain Weight to Build Muscle adds 84.7 g. Whichever way the result surprises you, audit the goal control before anything else.
Weight is the only field that can be left empty and still matter: the four selectors always hold a value, and Age is never read. With no weight the equation multiplies out to zero, which the page recognizes as a missing entry and answers with a check-your-inputs notice instead of printing a number.
Using the Free Protein Calculator Online
The tool runs entirely in the browser. There is nothing to install and no account to create; pressing Calculate loads one small formula module and the arithmetic happens on your own device.
Which Fields Change the Answer
Six inputs, three of which are live. Stating that plainly is better than letting you assume a personalization the equation does not perform.
| Field | Enters the calculation? | What it does |
|---|---|---|
| Weight (kg) | Yes | Multiplied directly — doubling it doubles the result |
| Fitness Goal | Yes | Supplies the factor: 0.8, 1.4 or 1.9 |
| Activity Level | Yes | Multiplies by 1.00, 1.10 or 1.20 |
| Age (years) | No | Recorded on the form; 25 and 68 return the same grams |
| Gender | No | Recorded on the form; male, female and other are identical |
| Diet Type | No | Recorded on the form; omnivore, vegetarian and vegan are identical |
Run it yourself and the point holds: a 70 kg person on Weight Loss and Moderate gets 107.8 g whether the entry says 25-year-old omnivore man or 68-year-old vegan woman. Age and sex do genuinely change protein requirements — the limits section below sets out how much — but this calculator does not model them, and implying otherwise would be worse than admitting it.
Turning the Number Into a Plan
Five steps take a screen reading into something you can act on at the next meal.
- Weigh yourself in kilograms, in the morning, before eating.
- Pick the goal that matches what you are doing this month, not the one you admire.
- Pick the activity level from your last four weeks of training, counting sessions you completed.
- Divide the result by your realistic number of eating occasions and write that per-meal figure down.
- Re-run it when your weight has moved by about 5 kg.
The last step matters more on a long diet than it looks. At the Weight Loss setting, 5 kg of body weight is worth 7.0 g of target at Sedentary, 7.7 g at Moderate and 8.4 g at Active. Each individual adjustment is trivial; three of them stacked up over six months is not.
Protein is a single line in a larger budget. To fix the total those grams belong inside, start with the Calorie Calculator.
Limits: When This Protein Target Does Not Apply
The formula is three numbers multiplied together. That simplicity is why it answers instantly, and it is also precisely where it stops being right.
Kidney Disease and Clinician-Set Targets
Chronic kidney disease is the clearest exception on this page. Protein restriction is part of standard management, and the target is set against measured kidney function by a clinician rather than by body weight and a goal selector. Liver disease, several metabolic disorders and dialysis each move the answer in different directions, sometimes upward.
The calculator has no field for any of this and no way to detect it. If a doctor or a registered dietitian has given you a protein figure, that figure wins outright — this page is not a second opinion on it.
Older Adults Need More Than the Maintenance Setting Gives
The PROT-AGE Study Group's 2013 position paper recommends 1.0 to 1.2 g/kg/day for healthy older people, above the 0.8 g/kg RDA, because aging muscle responds less strongly to the same dose of protein. It recommends more again for older adults who are ill or exercising regularly.
At 70 kg that band is 70 to 84 g a day, and nothing on this page lands in it. The closest setting from below is Maintain Weight plus Active at 67.2 g, 2.8 g short of the bottom. The next setting up, Weight Loss plus Sedentary, jumps to 98.0 g — 14.0 g past the top, and 1.4 g/kg against a recommendation of 1.0 to 1.2. Neither substitutes for the band, so multiply your own weight by 1.0 to 1.2 by hand, or take a figure from a clinician who knows your history.
Bodies Carrying a Lot of Fat, or Very Little
Grams per kilogram of total body weight overshoots when a large share of that weight is fat, which is metabolically undemanding compared with muscle. At 120 kg, the Build Muscle and Active combination returns 273.6 g a day — 1,094 calories of protein before a single gram of anything else is eaten. Practitioners scale by lean mass or by a target weight in these cases; this calculator cannot, because it never asks for body fat.
The opposite case has published numbers of its own. Helms and colleagues reviewed lean, resistance-trained athletes eating at a caloric deficit and argued for 2.3 to 3.1 g per kilogram of fat-free mass. That is defined against lean mass, not scale weight, so it cannot be compared with anything this page outputs until a body composition estimate exists.
To get the lean-mass estimate those athlete figures are built on, start with the Body Fat Calculator.
Pregnancy, Growth and Recovery
Pregnancy, breastfeeding, childhood and adolescence each carry their own reference intakes, and recovery from surgery, burns or serious infection raises requirements further still. MedlinePlus notes that conditional amino acids — the ones the body normally makes for itself — become necessary during illness and stress, which is the mechanism behind those higher figures.
None of those states is an input here. This tool is built for healthy, non-pregnant adults, and every number on this page should be read with that boundary attached.
Five Things the Number Is Not
- Not a minimum you fail by missing. Landing 10 g under on a given day is unremarkable and needs no correction.
- Not a ceiling with a warning attached. The ISSN position stand found no evidence of kidney or liver harm from above-RDA intakes in healthy exercising adults.
- Not a calorie plan. Grams of protein say nothing about the carbohydrate and fat filling the rest of your day.
- Not personalized by age, sex or diet, because none of those three fields reaches the equation.
- Not medical advice, and no substitute for a target set by a clinician who has your test results.
What it is: a defensible starting figure, derived from a published reference intake and two adjustments, that you can eat at for a few weeks and then correct against what the scale and the barbell tell you.