Why does the result change based on the ingredient?
A cup of flour weighs much less than a cup of honey, because each ingredient has a different density (grams per milliliter) — flour is light and aerated, while honey is dense and viscous. That's why converting by volume alone (cups, tablespoons) without accounting for the specific ingredient is one of the most common causes of recipes that don't turn out right, especially in baking, where the exact ratio of ingredients matters more.
Densities used
We use density values widely accepted in cooking references: water and milk close to 1g/ml; sifted all-purpose flour ≈ 0.5g/ml (1 cup ≈ 120g); granulated sugar ≈ 0.83g/ml (1 cup ≈ 200g); butter ≈ 0.95g/ml (1 cup ≈ 227g); oil ≈ 0.92g/ml; raw rice ≈ 0.75g/ml (1 cup ≈ 180g); honey ≈ 1.42g/ml. The standard cup used is 240ml (US standard, the most common in translated recipes).
These are average reference densities — the actual result can vary a bit depending on the ingredient brand, whether the flour was sifted or packed, etc. For precision baking, weighing ingredients on a scale is always more reliable than using cups.
Frequently asked questions
Why does my cup of flour sometimes weigh differently?
It depends on how the flour was scooped into the cup — sifted flour that's "spooned and leveled" (not packed) weighs much less than flour packed in with the scoop. This variation is one reason professional baking recipes prefer measuring by weight (grams) rather than volume.
Is a metric cup the same as a US cup?
Not exactly — a metric cup is typically 250ml, while the standard US measuring cup is 240ml. This calculator uses 240ml, the standard most commonly used internationally and in translated recipes; the difference is small enough not to matter for most home cooking.