Which gluten-free flour most closely replaces all-purpose wheat flour?

For most baking, a branded gluten-free all-purpose blend (Bob's Red Mill 1-to-1, King Arthur Measure for Measure, Cup4Cup) is the closest direct substitute. These are specifically formulated to mimic AP flour behavior and already contain a binding agent. Single-ingredient flours (almond, rice, oat) require more adjustment to the recipe and work better for specific applications than as generic AP replacements.

Why does the converter give more than 1 cup when I enter 1 cup of wheat flour?

Because the converter works by water absorption, not by weight alone. A flour that absorbs less liquid than wheat needs more volume to give the same structure; one that absorbs more (coconut, almond) needs less. The cup figure is that adjusted volume, and the gram figure is that volume weighed at the flour's own density.

What's the right amount of xanthan gum for my recipe?

It depends on the flour and recipe type. As a general guide: cookies need about 1/4 tsp per cup, quick breads and cakes need 1/4–1/2 tsp per cup, and yeast breads need 1/2–3/4 tsp per cup. Recipes using flours that already contain xanthan gum (most branded blends) need none added. The converter calculates the specific amount for your flour combination.

Can I use this for converting wheat cake flour or bread flour?

Yes. Pick the wheat flour your recipe calls for as the source. Cake, bread, pastry and whole-wheat flour are treated as equal in volume to all-purpose for substitution purposes (that is an estimate, and it is stated as one); what changes is the gluten-free flour you should pick for the job. Self-rising flour is the exception: convert the plain flour amount and add the leavening and salt back yourself.

Can I swap any gluten-free flour for any other gluten-free flour?

The calculator will give a number for any whole flour or blend, and will refuse where a number would mislead. Starches (tapioca, potato starch, arrowroot, cornstarch) are blend components and are never offered as the whole flour. Strongly absorbent flours such as coconut or lupin are capped at their maximum share and paired with rice flour. Baking mixes are not converted at all. Even where you get a number, swapping across categories (almond for rice, say) changes flavour, texture and fat, so treat it as a starting point.

I need to swap out a branded blend because it's not available. What should I use?

Most gluten-free all-purpose blends (Bob's Red Mill 1-to-1, King Arthur Measure for Measure, Cup4Cup, gfJules) are interchangeable in equal amounts; they're designed to behave similarly. The main variation is in liquid requirements and how they handle high-heat applications. Use this calculator to confirm the exact amount and check whether additional binder is needed.

Why does the calculator say to change my liquid amounts?

Because flours absorb water at different rates. When the target flour absorbs noticeably more or less than the one you are replacing, the calculator tells you which way to lean: hold back a little liquid and add it a spoonful at a time, or expect a looser batter. It does not claim an exact number of tablespoons; the right amount depends on the recipe, and coconut flour gets its own egg-and-liquid trial adjustment.

Do I need to change my binding agent if I swap gluten-free flours?

Possibly. Swapping from a blend that contains a gum to a plain single-ingredient flour means adding xanthan gum or psyllium husk; the calculator gives the amount for the converted cups, doubled for yeast bread and pizza. Swapping the other way means dropping the separate binder or the result goes gummy. For a few blends we have not confirmed the ingredient list, so the amount is shown as conditional: use it only if the package lists no gum.