Protein Intake Calculator

The formula this calculator uses

Protein (g) = bodyweight (kg) x grams per kg

W

Bodyweight in kilograms

r

Protein rate in grams per kilogram, roughly 0.8 to 2.0

P

Daily protein in grams, the product of the two

n

Meals per day, used to split the daily total

How to check the result by hand

1. 1

   Convert bodyweight to kilograms

   Every published rate is quoted per kilogram, so a weight in pounds must be converted first. One pound is 0.453592 kilograms, so 154 lb becomes 70 kg. Converting after the multiplication, or not at all, inflates the answer by 2.2046226218 times and lands on a number that looks plausible but is far too high.

2. 2

   Choose the rate that matches your situation

   Roughly 0.8 g/kg is the sedentary minimum, 1.2 to 1.6 g/kg covers most active adults, and up to about 2.0 g/kg is used when energy is restricted to protect lean mass. The choice moves the answer more than any arithmetic error can: for a 70 kg person the band spans 56 g to 140 g a day.

3. 3

   Multiply bodyweight by the rate

   70 kg x 1.6 g/kg = 112 g of protein per day. This is the single multiplication at the centre of the whole calculation, and it is worth writing out with units so that grams per day, not grams per kilogram, is the result.

4. 4

   Convert the grams to energy and to ounces

   At 4 kcal per gram, 112 g supplies 112 x 4 = 448 kcal. For imperial labels, 112 g divided by 28.349523125 gives 3.950683738353006 ounces. Both conversions start from the same gram figure, so a mistake there propagates into both.

5. 5

   Divide the total across meals

   Dividing 112 g over three meals gives 37.333333333333336 g per meal, close to the 30 to 40 g often cited as a practical serving. A different number of meals changes this figure without changing the daily total, which is the number that matters for the target.