Plain Flour (All-Purpose Flour) — Cups to Grams Conversion

Plain flour — called all-purpose flour in the United States and Canada — is the
most commonly used flour in home baking, and the ingredient most often
mis-measured by volume. It forms the structural backbone of cakes, biscuits,
and pastry, and even a small excess can make a bake dense or tough. Getting
the cups-to-grams conversion right matters most when following a recipe from
a different country, since British recipes typically give flour by weight
while American recipes typically use cups.

Flour's weight per cup depends heavily on how it is measured. Spooning flour
into the cup and levelling the top gives approximately 120g. Scooping the cup
directly into the bag compresses the flour and can reach 150g or more — a
20-25% difference that will noticeably affect texture. Sifting adds air and
reduces the weight further, to roughly 100g per cup. Humidity also plays a
small role, since flour absorbs moisture over time.

In the US and Canada this is "all-purpose flour." In the UK, Ireland, and
Australia it is "plain flour." Protein content varies slightly by country —
UK plain flour is typically 9–10% protein, US all-purpose flour 10–12% —
which can subtly affect texture in bread-adjacent bakes.

Cakes, biscuits, shortcrust pastry, pancakes, crumbles, and as a sauce/gravy
thickener or coating for frying.

Self-raising flour can replace plain flour if you omit any extra baking
powder the recipe calls for, since self-raising flour already contains it.