How Mealgebra counts

The 4/9/4 rule

The energy of macronutrients is fixed: protein — 4 kcal per gram, carbs — 4, fat — 9. Hence the check: calories = 4 × protein + 4 × carbs + 9 × fat.

Example: 100 g of a product has 2.8 g protein, 2.5 g fat, 4.7 g carbs. Compute: 4 × 2.8 + 9 × 2.5 + 4 × 4.7 = 52.5 kcal. If the label says 60 — something does not add up.

The estimate flag

When the stated calories differ from the macro-based computation by more than 25 %, Mealgebra recomputes them by the formula and flags the entry as an estimate. Smaller gaps stay as they are — ordinary rounding. Macros on labels are steadier than calories: they are measured directly, while calorie counts are often rounded.

Recomputing is not an accusation against the label. The 4/9/4 coefficients are Atwater factors — averages: fiber and organic acids yield slightly different energy, so a perfect match never exists. The estimate flag honestly says the figure was derived from the macros rather than taken on faith.

The exception is alcoholic drinks: ethanol energy (about 7 kcal per gram) is invisible to the formula, so their stated calories are kept — but only while the computation exceeds them by no more than 25 %: heavily understated values get recomputed as usual.

The daily target

The base metabolic rate follows the Mifflin–St Jeor formula: 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5 for men and − 161 for women. The result is multiplied by an activity factor — from 1.2 for a sedentary life to 1.9 for heavy physical work.

Example: a woman, 41 years, 170 cm, 65 kg, activity 1.55. Base: 10 × 65 + 6.25 × 170 − 5 × 41 − 161 = 1346.5 kcal. With activity: 1346.5 × 1.55 ≈ 2088 kcal a day. Losing, maintaining and gaining weight are ranges around that figure.

Household measures

“A glass”, “a tablespoon”, “a piece” fill in the grams for you: for milk a glass is 250 g, for cottage cheese a tablespoon is 20 g. Exact weight without scales — faster and more honest than “roughly a bit”.