This calculator gives you a rough calculation of the grams of protein you should be ingesting based on two different recommendations: the US government’s RDA (recommended daily allowance) and the United Nations’ World Health Organization (WHO).
The RDA is based on the ratio of 0.8 grams of protein per kilogram of lean body mass, while the WHO more conservatively recommends 0.66 grams of protein per kilogram of lean body mass. Since the RDA is an inflated number designed to exceed the protein needs of 98% of the population, the WHO number is probably closer to your true needs.
You may be surprised at how low your protein needs are, especially if you’ve used other protein calculators or have listened to trainers or read books on fitness. There are two big differences between this calculator and most of the others:
The most popular formula floating around these days is 1 gram of protein per kilogram of body weight. Now, 1 gram per kilogram may be appropriate for endurance athletes, babies, and the bedridden elderly, all of whom have slightly greater protein needs than the general public. But for everyone else, 1 gram per kilogram is way too much.
The much bigger misunderstanding is the use of body weight rather than lean body mass as the denominator. Our calculator asks for height and sex precisely so it can calculate your lean body mass using the body mass index (BMI).
(Side issue: BMI is not a great tool, since it doesn’t distinguish between muscle and fat, or large-boned from small-boned people. But unless you’re hugely muscled or the owner of a very large frame, that’s not going to be much of an issue.)
Using body weight, as almost everyone does, leads to dangerous inflation of protein requirements. Think about it. Let’s say you weigh 150 pounds (68 kg). Then you start gaining weight because you’re overeating. After a year, you weigh 200 pounds (91kg). Have you protein requirements changed? Almost not at all.
So we have a vicious cycle at play here. People believe they need way more protein than they really do. So they eat lots of animal products to get all that protein. The animal products lead to weight gain (see chapter 12 of Proteinaholic), which means people eat even more protein because they’re using the wrong formula. And so it goes, with added weight supposedly requiring added protein.
And since people believe that high protein diets are weight loss diets, they never question the relationship between their food choices and their increasing girth. Instead, they blame their weight gain on their “carb cheats.” Which occur, of course, because our bodies are built for carbs, and high protein, low-carb diets are biologically unsustainable.
There are lots of other factors besides the calculator inputs that determine your protein needs. If your level of physical activity is very high, if you are bedridden, or if you are a pregnant or lactating woman, you need more protein (possibly even more than the RDA).
Some medical conditions can require greater protein intake, or at least greater emphasis on certain amino acids. Obviously, a book, a calculator, and a website are no substitute for professional medical care. Use your own common sense and best judgment, and see a healthcare professional if you suspect a problem.