Nutrition
Energy contributed by protein
Protein supplies about 4 kcal per gram, so its contribution to a daily energy budget is the mass in grams multiplied by four.
The Formula
Calories (kcal) = protein (g) x 4
Protein supplies about 4 kcal per gram, so its contribution to a daily energy budget is the mass in grams multiplied by four.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| P | Protein mass | grams | In grams. The default case uses 112 g. |
| k | Energy density of protein | kcal per gram | Approximately 4 kcal per gram, the standard Atwater value used on nutrition labels. |
| E | Energy from protein | kcal per day | At 4 kcal per gram, 112 g supplies 448 kcal in a day. |
What Each Symbol Means
Pgrams
Protein mass
In grams. The default case uses 112 g.
kkcal per gram
Energy density of protein
Approximately 4 kcal per gram, the standard Atwater value used on nutrition labels.
Ekcal per day
Energy from protein
At 4 kcal per gram, 112 g supplies 448 kcal in a day.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate protein intake page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Protein Intake, filed under Health. Every number the guide produces comes from substituting into this one line.