Sourdough Hydration Calculator
The Sourdough Calculator works out the exact flour, water, starter, and salt for your loaf using baker's percentages — the method professional bakers use, where every ingredient is a percentage of the total flour weight. Enter one flour amount and the whole recipe scales with it.
Beyond the gram amounts, it shows your true hydration (the flour and water hidden inside your starter), builds your levain from a feed ratio, and lays out an 8-step baking timeline tuned to your kitchen temperature. It is built for home bakers — from a first 70% loaf to high-hydration, whole wheat, and rye doughs.
How to Use the Sourdough Calculator
Choose a recipe preset
Pick a starting point: Basic Sourdough (70% hydration), High Hydration (80%), Whole Wheat (75%, 25% starter), or Rye (65%). Each preset loads sensible hydration, starter, and salt percentages you can then tweak.
Set your flour amount
Enter the total flour weight in grams, or switch to By Number of Loaves and set how many loaves and the weight per loaf — the calculator back-solves the flour you need.
Adjust the percentages
Fine-tune Hydration, Starter, and Salt with the input fields or the sliders. The Recipe Results — and the true hydration figure — update instantly with every change.
Build your levain
Use the Levain Builder to size your levain from a feed ratio (default 1:5:5, seed:flour:water). It adds a 10% buffer so you always have a little extra to spare.
Follow the timeline
Set your room temperature to Warm or Cool and follow the 8-step schedule, from feeding the levain through the final bake. Durations adjust to match your kitchen.
Features
Baker's Percentage Calculator
Computes the exact grams of flour, water, starter, and salt from your percentages, plus the total dough weight.
Flexible Input Modes
Work by flour weight when you know your flour, or by number of loaves and weight per loaf for a target yield.
Recipe Presets
Start from Basic Sourdough, High Hydration, Whole Wheat, or Rye, then customize every percentage to taste.
Interactive Sliders
Drag the hydration, starter, and salt sliders or type exact values — results recalculate live as you move them.
True Hydration Display
Shows both the apparent hydration you set and the true hydration, accounting for the flour and water inside your starter.
Levain Builder
Sizes the seed starter, flour, and water for your levain from a custom feed ratio, with a built-in 10% buffer.
8-Step Baking Timeline
A full schedule from feeding the levain to pulling the loaf from the oven, with a duration for each stage.
Temperature Adjustment
Toggle between warm and cool rooms and the timeline durations shift to match your kitchen for accurate timing.
Frequently Asked Questions
What is baker's percentage?
Baker's percentage expresses each ingredient as a percentage of the total flour weight. For example, 70% hydration means 70g of water for every 100g of flour. Because flour is always 100%, you can scale a recipe to any size by changing just the flour amount.
What is sourdough hydration, and what should I use?
Hydration is the water as a percentage of flour. Beginners should start around 65–70% for a manageable dough; with experience, try 75–85% for a more open crumb. Whole wheat and rye absorb more water, so they usually need a higher figure — the Whole Wheat and Rye presets are tuned for this.
What is the difference between apparent and true hydration?
Apparent hydration is the water percentage you set in the recipe. True hydration also counts the flour and water already in your starter — assumed to be a 100% hydration starter, meaning 50/50 flour and water — so it is always a little higher. The calculator shows both figures side by side.
How much starter (levain) do I need per loaf?
Starter is set as a percentage of flour — most presets use 20% (Whole Wheat uses 25%). A higher percentage ferments faster; a lower percentage is slower and gentler. Enter your loaves and the calculator gives the exact grams of levain, then the Levain Builder shows how to grow that amount from your seed starter.
What feed ratio should I use for my levain?
The default 1:5:5 (1 part seed, 5 parts flour, 5 parts water) suits most schedules. Use a lower ratio like 1:3:3 for faster fermentation, or a higher one like 1:10:10 to slow things down for an overnight build. A 1:1:1 ratio peaks quickly and is handy for refreshing a sluggish starter.
How much salt should I use?
The standard range is 1.8–2.2% of flour weight, and most bakers settle on 2%. Less salt gives a milder flavor and faster fermentation; more salt slows fermentation and deepens flavor. The presets sit within this range.
Why does the timeline change with temperature?
Fermentation speed depends on temperature. A warm room (24–27°C) speeds up yeast and bacterial activity, while a cool room (18–21°C) slows it down. Set the timeline to match your kitchen and the stage durations adjust so your timing stays accurate.
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