Skip to main content

Methodology

How FlourSwap Works

Where the numbers come from, how the calculations work, and how the flour database is maintained.

Data Sources

The flour database draws from three categories of sources, used based on what type of flour is being profiled:

1. USDA FoodData Central (FDC)

Protein content and nutritional composition for single-ingredient flours (rice flour, almond flour, tapioca starch, etc.) are taken from USDA FDC entries where one exists. Those figures describe composition, not baking behaviour: nothing in FDC tells you how much almond flour replaces a cup of wheat, and we do not claim it does.

2. Manufacturer Product Specifications

Branded blend profiles (Bob’s Red Mill 1-to-1, King Arthur Measure for Measure, Caputo Fioreglut, etc.) use protein and composition data from manufacturers’ published product specifications and nutritional labels. Gram-per-cup densities for branded blends are sourced from manufacturer baking resources where published, or determined from nutritional label serving sizes.

3. Manufacturer Guidance and Published Baking Practice

Substitution factors and binder starting amounts are estimates drawn from manufacturer usage guidance and widely published gluten-free baking practice (King Arthur Baking’s gluten-free guides among them). Each flour records where its factor came from; where a manufacturer states a usage, that is cited, and everything else is marked as an estimate. We have not run controlled comparison bakes, and the site does not say otherwise.

4. Certification Labels

Certification labels shown on flour profiles reflect product packaging and manufacturer statements: GFCO (the strictest standard at <10 ppm) or FDA gluten-free labeling (<20 ppm). FlourSwap does not independently verify certification, and a label on a generic flour category never guarantees the specific bag in your hand. Bakers with celiac disease should check the package and the manufacturer directly.

How Conversions Are Calculated

FlourSwap converts by a per-flour substitution factor, then weighs the result. Here is exactly what runs when you press Convert, and when the converter will not give you a number.

Why a straight cup-for-cup swap fails

Single-ingredient gluten-free flours do not do the job of wheat flour at the same volume. Almond flour is used at roughly three quarters of the wheat volume, oat flour at more than the wheat volume, coconut flour at about a quarter. Only formulated 1-to-1 blends are built to swap cup for cup. The converter encodes that, one number per flour.

The substitution factor

Every flour in the database carries a volume substitution factor relative to all-purpose wheat flour. One cup of wheat is replaced by 1 ÷ factor cups of the flour. A conversion between any two flours is:

  1. Volume: your amount in cups × source factor ÷ target factor. If you entered grams, the amount is first turned into cups using the source flour’s weight per cup.
  2. Weight: that volume weighed at the target flour’s own grams per cup. The gram figure is the one to bake from.
  3. No hidden adjustments: the recipe type you choose never changes the flour quantity. It changes the binder amount, the yeast warnings, and the advice text.

Formulated 1-to-1 blends (Bob’s Red Mill 1-to-1, King Arthur Measure for Measure, and the rest) have a factor of exactly 1, so a cup of wheat becomes a cup of blend in every recipe type. The factors for single-ingredient flours are estimates taken from manufacturer usage guidance and widely published gluten-free baking practice; each flour records where its number came from, and none of them is a laboratory measurement.

When the converter refuses to give a number

  • Starches (tapioca, potato starch, arrowroot, cornstarch) are blend components. Asked to use one as the whole flour, the converter explains the blend share instead of inventing a quantity.
  • Capped flours (coconut, lupin, hemp, chestnut, mesquite, quinoa, sweet potato, sweet rice) work only as part of the flour. The converter returns a starting blend: the capped flour at its maximum share, rice flour for the rest, scaled so the total still replaces your wheat amount. Coconut flour also carries a trial adjustment for eggs and liquid.
  • Baking mixes and products designed for their own recipes (Caputo Fioreglut) are not converted at all; use the recipe on the package.
  • Self-rising flour carries its own leavening and salt, so the converter asks you to convert the plain flour amount and add those back.

Precision

The engine keeps full precision internally. Cups are shown to the nearest eighth or third with a spoon remainder when the fraction alone would be off by more than a teaspoon, amounts under an eighth of a cup are shown in spoons, and grams are whole grams. Converting a flour to another and back returns the amount you started with.

Binding Agent Calculations

Xanthan gum and psyllium husk replace gluten’s structural job. FlourSwap uses one rule for every tool:

  • Starting amount per cup: each flour has a xanthan gum and a psyllium husk amount per cup (most single-ingredient flours ¼ tsp xanthan; almond flour can use an extra egg instead).
  • Multiply by the converted cups: including every component of a capped blend.
  • Double it for yeast bread and pizza.
  • Scale it with the recipe: doubling the recipe doubles the binder. There is no diminishing-returns rule; the amount stays a fixed share of the flour.

Blends that already contain a gum get no extra binder. For a few blends we have not confirmed the ingredient list; those show a conditional amount to use only if the package lists no gum. Xanthan and psyllium are alternatives, not additions. If your recipe already lists a binder, keep that line and scale it with the recipe rather than adding a second one.

Known Limitations

FlourSwap conversions are starting points, not guaranteed results. Several factors affect real-world baking outcomes that the calculator cannot account for:

  • Altitude: Higher altitudes require less leavening and shorter baking times. The bread guide accounts for altitude, but the flour converter does not.
  • Humidity: High-humidity kitchens can cause gluten-free flours to absorb moisture from the air during mixing, affecting final texture.
  • Milling fineness variation: The same flour from different brands can have different particle sizes, affecting absorption and texture. The database records standard specifications; super-fine-milled variants may behave differently.
  • Egg and fat interactions: Recipes with high egg or fat content interact differently with gluten-free flours. The converter does not adjust for these interactions.

If a conversion produces an unexpected result, the Baking Troubleshooter and Bread Diagnosis tools can help identify what went wrong and what to adjust.

Frequently Asked Questions

Where does FlourSwap's flour data come from?

Densities (grams per cup) come from manufacturer specifications and USDA FoodData Central where available. Substitution ratios are estimates drawn from manufacturer usage guidance and widely published gluten-free baking practice; each flour records where its ratio came from. Certification labels reflect product packaging and manufacturer statements; FlourSwap does not independently verify certification.

How does FlourSwap calculate gluten-free flour conversions?

Every flour carries a volume substitution factor relative to all-purpose wheat flour: one cup of wheat is replaced by 1 divided by that factor in cups of the flour. A conversion multiplies your amount by the source factor and divides by the target factor, then weighs that volume at the target flour's own density to give grams. Formulated 1-to-1 blends have a factor of exactly 1. Starches and baking mixes are never given as whole-flour replacements, and strongly absorbent flours such as coconut are capped and paired with rice flour.

How are binding agent amounts calculated?

One rule: each flour has a starting xanthan gum (and psyllium husk) amount per cup; the converter multiplies it by the converted cups, doubles it for yeast bread and pizza, and scales it in proportion when you scale a recipe. Blends that already contain a gum get no extra binder. Products whose ingredient list we have not confirmed get a conditional amount to use only if the package shows no gum.

How often is the flour database updated?

The database is updated when manufacturers publish formulation changes, when certification data changes, or when bakers report discrepancies. Branded blend profiles are reviewed most frequently since manufacturers reformulate more often than single-ingredient flours change.

Why does the converter give different amounts than 1:1 cup substitution?

Because most single-ingredient gluten-free flours do not stand in for wheat cup for cup. Almond flour, for example, is used at about three quarters of the volume, while oat flour is used at more. The factor behind each flour encodes that. Branded 1-to-1 blends are the exception: the converter returns exactly one cup for one cup, and the gram figure simply reflects the blend's own weight per cup.

Data Corrections

If you find a discrepancy between our flour data and your results or manufacturer specs, please let us know. Bakers catching errors improves the database for everyone.

Send a correction