Sourdough Calculator

How to use this sourdough calculator

What this calculator does

This calculator turns a small set of baker's-math inputs into a reproducible sourdough formula. It calculates how much starter and salt to use from the base flour, splits that starter into its flour and water components, and then reports the true total flour, total water, total dough weight, and total hydration. The hydration result includes the starter's contribution, which matters whenever a preferment contains a meaningful share of the recipe. It is a recipe-scaling and formula-checking tool, not a prediction of fermentation time, loaf volume, proof readiness, flavor, or bake quality.

When to use it

Use it when you are scaling a familiar loaf up or down, checking whether two formulas really have the same hydration, converting a recipe that lists starter separately from total flour and water, or testing how a stiffer or looser starter changes the final dough. It is also useful for recording repeatable test bakes because every displayed quantity can be exported to a real Excel workbook.

How to calculate

1. The calculator opens with a complete demonstration: 500 g Flour, 335 mL Water, 20% Percentage starter, 100 g Starter, and 100% Starter hydration. The results and Download Excel action are ready immediately.
2. Replace the demonstration values with your own recipe. Results update live; no separate Calculate button is needed.
3. Read Total hydration first, then check Starter, Salt, Starter flour, Starter water, Total dough weight, Total flour, and Total water. The breakdown table shows each ingredient added to the bowl and its baker's percentage.
4. Select Download Excel to export the current validated recipe. Reset clears all five input fields, removes calculated results, and may disable Download Excel until a complete valid recipe is entered again.

For the underlying convention, King Arthur Baking's baker's percentage reference explains why flour is treated as 100% and other ingredients are expressed relative to flour weight.

Input guide

Flour is required and is entered as a positive gram weight from more than 0 up to 100,000 g. A realistic value is 500 g. It is the base for Percentage starter and the fixed 2% salt calculation, so increasing Flour scales Starter and Salt proportionally. Enter plain decimal numbers using a period as the decimal separator; grouped values such as 1,000 are accepted, but ambiguous decimal-comma input is rejected.

Water is required and is entered in milliliters from 0 to 100,000 mL. A typical example is 335 mL. Raising Water raises both the direct-water baker's percentage and Total hydration, but it does not change Starter or Salt. The model follows the recipe convention that 1 mL of water is approximately 1 g for baker's-percentage and dough-weight arithmetic. For maximum production precision, you can weigh water and enter the numerically equivalent gram value as milliliters.

Percentage starter is required when it is the last starter field you edit and accepts 0% to 100%. The demonstration uses 20%. It means starter weight divided by base Flour, not the fraction of total dough. Raising it increases Starter and Total dough weight and also changes Total flour and Total water because the starter itself contains both. A percent sign may be typed, but do not enter a decimal fraction such as 0.20 when you mean 20%. Percentage starter and Starter are linked, so editing this field recalculates Starter.

Starter is the linked starter-weight field in grams. It is required when it is the last of the two linked starter fields you edit, accepts 0 to 100,000 g, and must not exceed Flour under this calculator's 0% to 100% starter-percentage range. The demonstration is 100 g. Editing Starter recalculates Percentage starter from Starter ÷ Flour × 100. This lets you use a known levain weight directly instead of first converting it to a percentage. Do not add the starter's flour and water separately here; Starter is their combined weight.

Starter hydration is required and accepts 0% to 300%. The example uses 100%, meaning equal flour and water by weight inside the starter. Higher starter hydration shifts a fixed starter weight toward more water and less flour; lower hydration does the opposite. It changes Starter flour, Starter water, Total flour, Total water, and Total hydration, but not the total Starter weight. A 1:1 flour-to-water starter is 100% hydration, not 50%.

Output guide

Total hydration is the primary result: total water divided by total flour, shown as a percentage. The Starter result card mirrors the linked Starter input; when Percentage starter drives the pair it equals base Flour multiplied by Percentage starter, and when Starter drives the pair the percentage is recalculated from that weight. Salt is 2% of base flour. Starter flour is shown in grams and Starter water in milliliters; they are the two parts of the starter implied by Starter hydration. Total dough weight is the sum of Flour, Water, Starter, and Salt using the 1 mL water ≈ 1 g convention. Total flour adds base Flour and Starter flour; Total water adds direct Water and Starter water and is shown in milliliters. A zero water input can legitimately produce very low hydration, while unusually high hydration is an arithmetic result rather than a recommendation for a specific flour or skill level.

The Baker's math breakdown table has four columns: Ingredient names the component added to the dough; Baker's percentage shows that component relative to base Flour; Amount gives the numeric quantity; and Unit distinguishes grams from milliliters. The Total additions row sums the direct ingredient quantities using the calculator's 1 mL water ≈ 1 g mass convention. These are exact identities from the entered formula, subject only to display rounding.

Worked example

With the startup values, 20% of 500 g Flour gives 100 g Starter, and 2% of 500 g gives 10 g Salt. At 100% Starter hydration, that 100 g starter contains 50 g flour and 50 mL water under the 1 mL ≈ 1 g convention. Total flour is therefore 500 + 50 = 550 g, while total water is 335 + 50 = 385 mL. Total hydration is 385 ÷ 550 × 100 = 70.00%. Total dough weight is 500 + 335 + 100 + 10 = 945.00 g. The first-open cards, breakdown table, and exported workbook all use those same values.

Learn more

Total hydration should include flour and water from the starter or preferment, not only what is added directly to the final mix; this bread hydration guide walks through that accounting. For practical starter maintenance and bread-making context, see Colorado State University Extension's sourdough basics.