Why "parts" instead of cups or a fixed weight
A ratio like "3 parts flour : 2 parts liquid : 1 part fat" describes a scone's structure independent of batch size — the same ratio makes one scone's worth of dough or fifty, because "a part" is just whatever unit weight you decide it is. Set 1 part to 50g and you get a small batch; set it to 200g and you get a large one, with every ingredient scaling together automatically. This is the same idea as baker's percentage, generalized beyond bread to pancakes, biscuits, pasta, and more — each with its own characteristic ratio instead of flour fixed at 100%.
What "liquid," "fat," and "egg" mean here
These ratios describe a role, not one specific ingredient — "liquid" is typically milk, buttermilk, or water depending on the recipe; "fat" is typically butter or oil; "egg" is measured by weight (a large egg is about 50g) rather than by count, so the ratio holds even if your eggs run a bit large or small. Swapping within a role (milk for buttermilk, butter for oil) mostly holds; changing the ratio itself changes the texture the recipe is known for.
FAQ
Why does bread only list two ingredients? The classic 5:3 flour-to-liquid ratio is bread's core structural ratio — salt and yeast are added in small, separate amounts relative to the flour rather than as part of the base ratio itself. See our baker's percentage calculator for those smaller amounts specifically.
Why does pie dough list "liquid" instead of "water"? Ice water is standard, but some recipes use a splash of vodka or vinegar alongside it to limit gluten development — "liquid" covers either approach at the same 3:2:1 flour-to-fat-to-liquid ratio.