Cooking methodology

The Cooking clusterhas two moving parts: ingredient density (which depends on the ingredient and how you measured it) and cup volume (which depends on which country’s convention you’re using). This page explains where both numbers come from.

Ingredient density data sources

Our density table covers 36 common ingredients. Sources, in order of authority for each ingredient type:

• USDA FoodData Central — the canonical authoritative source for flour, sugar, salt, oil, water, and most pantry staples. We use the unprocessed-form density (e.g., AP flour rather than self-rising).
• King Arthur Baking — the practical reference for baking ingredients (cocoa powder, baking soda, yeast, leavening agents). Their numbers come from extensive in-house testing.
• BBC Good Food — the cross-check for UK- conventional ingredients (golden syrup, treacle, double cream) where US sources are inconsistent or absent.

Where sources disagree (which happens for compressible ingredients like flour), we use the median of the available figures. The disagreement is itself meaningful — it’s the reason every serious cookbook now publishes in grams.

The cup volume question

Even after you fix the ingredient, “cup” means different volumes depending on the recipe’s country of origin:

• US customary cup: 236.59 ml (8 US fluid oz)
• US legal cup (on most US measuring cups): 240 ml
• UK metric cup: 250 ml
• UK imperial cup (rare, historical): 284 ml
• Australian cup: 250 ml
• Japanese cup: 200 ml

Our converter defaults to the US customary cup because that’s the dominant convention in recipes searched in English. The cup-type dropdown lets you override; see our US vs UK cup comparison for the full breakdown.

The packing problem

Dry ingredients vary in density depending on how the user scooped them. Flour can pack 25% denser than its un-tapped, unsifted state. Brown sugar is often measured “packed” (compressed firmly into the cup) rather than spooned. Powdered sugar is often sifted before measuring.

Our density values assume the “spoon and level” method — gently spoon the ingredient into the measuring cup without compacting, then level the top with a straight edge. This is the convention King Arthur Baking documents and most modern US cookbooks follow.

Output accuracy: within ±5% for the typical ingredient and measurement method, which is well inside the tolerance most recipes can absorb. For precision baking (souffles, perfect sourdough hydration), measure on a scale — our converter is a starting point, not a substitute.

Oven temperature math

See the broader units methodology for the Celsius ↔ Fahrenheit conversion. Gas Mark uses the canonical British table (Mark 1 = 275°F = 135°C, then 25°F per mark up to Mark 9 = 475°F). For non-standard temperatures, the calculator interpolates linearly between the two adjacent Gas Mark steps.