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Sourdough Hydration Calculator

Find your sourdough dough's true total hydration percentage by entering the recipe flour, water, starter weight, and starter hydration, with the starter's own flour and water counted in full.

Set to 0 to exclude the starter.

100 for a standard 1:1 starter.

Result

72.7%

350 g water and 500 g flour, including the starter's contribution, gives a total dough hydration of 72.7 percent

Quick Answer

Sourdough hydration is total water divided by total flour, multiplied by 100. Total means including the water and flour inside the starter: a 100 g starter at 100 percent hydration contributes 50 g flour and 50 g water. For 500 g flour, 350 g water, and 100 g starter at 100 percent hydration, total water is 400 g and total flour is 550 g, giving a hydration of 72.7 percent. Leaving the starter out of the calculation understates true hydration.

Sourdough Hydration Explained: What It Actually Measures

Sourdough hydration is the total water content of a dough expressed as a percentage of its total flour content, following the baker's percentage system where all ingredients are measured relative to flour. Most recipes state a hydration figure, but that figure is only correct if it includes the water and flour contributed by the sourdough starter itself, not just the separately added flour and water in the recipe. This is the most common hydration-calculation error in home baking: treating the starter as a single opaque ingredient rather than as a pre-fermented mixture of water and flour. A 100 percent hydration starter (the most common type, also called a 1:1 or equal-parts starter) is exactly half water and half flour by weight. Ignoring that means your stated hydration is lower than the hydration the dough actually experiences, which affects rise, crumb structure, and shaping behaviour. This calculator solves that correctly. It splits the starter into its flour and water components using the starter's hydration percentage, adds those to the main recipe flour and water, and computes the true total hydration. The result displays on a 50 to 130 percent gauge with three named zones: Stiff (50 to 65 percent), Standard (65 to 80 percent), and Wet (80 to 130 percent).

How Total Sourdough Dough Hydration Gets Calculated

Total hydration (%) = (Total water ÷ Total flour) × 100. Total water includes recipe water plus starter water; total flour includes recipe flour plus starter flour.

  • Total hydration (%) = (Total water ÷ Total flour) × 100.
  • Total water = recipe water (g) + water from starter (g).
  • Total flour = recipe flour (g) + flour from starter (g).
  • Starter flour = starter weight × (100 ÷ (100 + starter hydration %)).
  • At 100% starter hydration (1:1 starter): starter flour = starter weight ÷ 2, starter water = starter weight ÷ 2.

Using This Sourdough Hydration Calculator: Step By Step

Inputs

  • Recipe flour weight in grams (not counting flour in the starter).
  • Recipe water weight in grams (not counting water in the starter).
  • Total weight of starter added in grams (set to 0 if no starter used).
  • Starter hydration percentage (default 100 for a standard 1:1 starter).

Steps

  1. Enter the flour weight from your recipe in grams.
  2. Enter the water weight from your recipe in grams.
  3. Enter the starter weight. If you are not using starter, set this to 0.
  4. Confirm the starter hydration percentage (leave at 100 for a standard 1:1 starter).
  5. Read the total hydration percentage and see its zone on the gauge (Stiff, Standard, or Wet).

Sourdough Hydration Example, Worked In Full Detail

500 g flour, 350 g water, 100 g starter at 100% hydration

  1. Split starter: 100 g starter at 100% hydration = 50 g flour + 50 g water.
  2. Calculate total flour: 500 g (recipe) + 50 g (starter) = 550 g.
  3. Calculate total water: 350 g (recipe) + 50 g (starter) = 400 g.
  4. Calculate hydration: (400 ÷ 550) × 100 = 72.73%.

72.7 percent total hydration (Standard zone). Uncorrected simple calculation (350 ÷ 500 = 70.0%) understates hydration by 2.7 percentage points.

Where This Sourdough Hydration Calculator Is Most Useful

Use this calculator when troubleshooting a dough that feels wetter or drier than your recipe's stated hydration, when adapting a recipe to a starter with a different hydration (stiff starter, liquid levain), or when scaling a recipe and needing to maintain a target hydration exactly. It is also useful when comparing recipes from different sources that may state hydration figures with or without the starter counted in.

For other math calculations, visit the math calculators hub, and check the glossary for definitions of common technical terms.

Assumptions

  • Starter hydration default of 100 percent represents a standard equal-parts-by-weight (1:1) starter.
  • The starter split formula assumes the stated hydration is accurate for your actual starter.
  • All weights are in grams; ratios are mass-based (Baker's Percentage is by weight, not volume).
  • No accounting for autolyse, prefermented flour, or levain-within-levain calculations.

Limitations

  • Assumes a single starter at a uniform hydration; does not handle multi-stage builds or mixed-hydration starters.
  • Does not output a full recipe; use the Sourdough Calculator for that.
  • Does not account for flour absorption variation by type (whole wheat absorbs more than white, rye more than whole wheat), only the arithmetic hydration figure.

In Practice

The single most common hydration mistake is running a recipe at a higher hydration than intended because the starter was not counted in. A baker who adds 200 g of 100 percent hydration starter and calculates hydration on recipe flour and water alone is effectively working with 100 g of extra water that they did not account for. That gap widens with larger starter quantities, such as in high-hydration or slow-ferment recipes that use 20 to 30 percent of flour weight as starter. Always split the starter in your hydration calculation. The starter's own flour and water change both the denominator and the numerator, and both matter for the final percentage.

Related Calculators

Sourdough Calculator

Find the water, starter, salt, and total dough weights for a sourdough batch from flour weight and baker's percentages for home baking.

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Sourdough Starter Calculator

Find the exact gram weights of starter, flour, and water for any feeding ratio and target total weight, whether you use a 1:1:1, 1:2:2, or any other parts-based feed.

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Related Guides

Sourdough Hydration Calculator: Frequently Asked Questions

Why Does the Starter Affect Total Dough Hydration?

The starter is a mixture of flour and water in a specific ratio (its hydration percentage), not an indivisible ingredient. When it goes into a dough, its water and flour join the total dough water and flour. A 100 g starter at 100 percent hydration adds 50 g of water and 50 g of flour to the dough. Ignoring that means the calculated hydration is lower than the actual dough hydration, which can lead to unexpected handling and fermentation behaviour.

What Hydration Is Right for Sourdough Beginners?

Most sourdough guides recommend 65 to 75 percent total hydration for beginners, sitting in the lower to mid Standard zone. Doughs in this range hold their shape during shaping and are easier to build tension on. Doughs above 80 percent (the Wet zone) require more experience with handling techniques like stretch-and-fold or coil folds to develop adequate structure without deflating the dough.

How Do I Know If My Starter Is 100% Hydration?

A 100 percent hydration starter is fed by equal weights of flour and water each time. For example, feeding 50 g starter with 50 g flour and 50 g water produces a 100 percent hydration starter. If your feeding ratio uses different amounts of flour and water, calculate your starter's hydration as (water weight ÷ flour weight) × 100 and enter that figure in the starter hydration field.

How Is This Calculator Different From the Sourdough Calculator?

The Sourdough Calculator takes a target hydration percentage and outputs a complete recipe (how much flour, water, and starter to use). This calculator does the opposite: it takes an existing recipe and finds the true hydration percentage that recipe produces, including the starter's contribution. Use the Sourdough Calculator to build a recipe from scratch; use this one to check the hydration of a recipe you already have.

Can I Use This Calculator for Discard Recipes?

Yes. If a recipe uses sourdough discard and specifies a weight, enter that weight as the starter weight along with the discard's hydration (usually 100 percent for a standard starter). The flour and water from the discard will be included in the total hydration calculation. If the discard amount is small, the effect on total hydration will be minor but still worth accounting for in a precise recipe.

Sources

Last updated: . Reviewed for accuracy against the formula shown above.