Protein Calculator

How to use the protein calculator

Choose US or metric units first. That choice changes the height boxes (feet and inches, or centimetres and metres) and whether the answer is given in ounces or grams. The weight box has its own kg / lb selector, so check it matches the figure you entered.

Fill in age, sex, height and weight, pick the activity level that describes a normal week, and set the Proteins percentage. The box starts at 25% and accepts 10% or more. Only weight is required; a blank age or height is read as zero and pulls the answer down, so enter both.

You get five lines, each stating the Calories that protein should supply and the matching amount per day: one for staying at your current weight, two for losing weight (budgets 500 and 1,000 Calories lower) and two for gaining (500 and 1,000 Calories higher). The weekly rates in the labels are approximate; a pound of body weight is often estimated at about 3,500 Calories, so use them as starting points and adjust from your own results.

Very small, inactive people can see negative amounts in the deficit rows, because the reduced budget drops below zero. Treat that row as unrealistic and pick a gentler one.

How the protein figure is worked out

The calculator estimates your resting energy use with the Mifflin-St Jeor equation, multiplies it by an activity factor (1.2 sedentary, 1.375 light, 1.55 moderate, 1.725 high, 1.9 extreme) to get daily Calories, then gives protein its share. Protein supplies 4 Calories per gram.

BMR (men) = 10 × kg + 6.25 × cm − 5 × age + 5; BMR (women) = 10 × kg + 6.25 × cm − 5 × age − 161

protein grams = daily Calories × protein share ÷ 100 ÷ 4 (ounces = grams ÷ 28.35)

Worked example. A 30-year-old man, 5 ft 10 in and 180 lb (81.6 kg), exercises lightly. His BMR is 1,783 Calories and his daily need is 1,783 × 1.375 = 2,451 Calories. At 25% protein, 2,451 × 0.25 = 613 Calories, and 613 ÷ 4 = 153 g (5.4 oz) per day. Divided by his weight that is 153 ÷ 81.6 = 1.9 g per kilogram, which is generous for a non-athlete and sits in the range used for people who lift weights.

The percentage and the grams-per-kilogram views do not always agree. The same 25% on a lower calorie budget gives fewer grams, so someone dieting hard can end up with less protein per kilogram than they intended. If you would rather fix the amount by body weight, use the protein requirement calculator.

What protein does

Proteins are long chains of amino acids. Your body uses 20 of them, and nine are essential, meaning you must get them from food. Protein builds and repairs muscle, skin and organs, makes enzymes and many hormones, supports the immune system and carries oxygen in blood.

Animal foods (meat, fish, eggs, dairy) supply all the essential amino acids. Most single plant foods are low in one or two of them, but combining legumes with grains or nuts over the day covers the full set, and soy is a complete source by itself.

How much protein is enough?

The US recommended dietary allowance for healthy adults is 0.8 g per kilogram of body weight a day, which is the amount that prevents deficiency for nearly everyone. For the 81.6 kg man in the example that is 65 g, only about 10.7% of his Calories. The broader acceptable range for protein is 10% to 35% of Calories.

Several groups are advised to go higher:

• Older adults: a position paper from the PROT-AGE group suggests 1.0 to 1.2 g/kg a day to offset the gradual loss of muscle with age.
• Athletes and regular trainers: sports nutrition bodies suggest roughly 1.2 to 2.0 g/kg, depending on the sport and training load.
• People in a calorie deficit who want to keep muscle: toward the upper part of those ranges.

Very high intakes are probably safe for healthy people, but evidence for long-term use well above 2 g/kg is limited, and people with kidney disease are usually told to restrict protein. If you have a medical condition, check with a doctor first.

These are estimates, not individual medical advice. Pregnancy, kidney or liver problems and eating disorders all change protein needs. See the disclaimer.

Protein in common eating patterns

These are the protein shares used by the presets in the macro calculator, converted to grams on a 2,000 Calorie day:

Higher-protein patterns tend to make meals more filling, which some people find useful when cutting Calories. Whichever split you use, the amount in grams matters more than the label.

Protein and building muscle

Muscle grows when resistance training is paired with enough protein and enough total energy. A meta-analysis of 49 trials found that extra protein improved gains from lifting up to roughly 1.6 g/kg a day, with little added benefit beyond that on average. Spreading the intake over three or four meals, each with a sensible serving of protein, is a common way to reach it.

For a 75 kg lifter, 1.6 g/kg is 120 g a day; at 2,800 Calories that is 480 Calories, or about 17% of the total. That is well inside the 10-35% window, so a lifter eating enough overall rarely needs to push the percentage very high. Track your strength with the 1-rep max calculator to see whether the plan is working.