Almost every recipe site shows a tidy block of numbers: calories, protein, carbs, fat. Very few of those numbers come from a laboratory. They are computed from an ingredient list, and every step of that computation introduces uncertainty.

That does not make them useless. It does mean you should treat them as a rough scale rather than a measurement.

Where the uncertainty comes from

• Portion size. "Serves four" is an editorial decision, and the per-serving figure moves directly with it.
• Ingredient vagueness. "One medium onion" or "a drizzle of oil" can differ by a factor of two between two cooks.
• Cooking losses. Fat rendered out of meat, water evaporated from a sauce, and oil left in the pan all change the final plate.
• Database matching. "Cheddar" covers a wide range of products with meaningfully different fat content.

How our numbers are produced

The public recipe database behind Recipe Finder does not supply nutrition data at all. Where a figure is missing, we derive an approximation from the ingredient list, and we label it as an estimate rather than presenting it as fact. Cooking time and serving counts are derived the same way.

We would rather tell you the number is approximate than quietly imply a precision we do not have.

Using estimates well

• Compare relatively. "This dish is heavier than that one" is reliable; "this dish is 412 calories" is not.
• Watch the fat and sugar you add yourself. That is usually the largest uncounted variable.
• Check allergens against the actual ingredient list, never against a dietary tag.