This free sourdough calculator handles the two bits of maths every baker gets stuck on: how much flour and water to feed your starter, and how much water, salt and starter to weigh out for a loaf. Pick a mode above, type your numbers in grams, and the amounts update as you go. New to sourdough? Start with my simple sourdough starter recipe, then come back here when it is time to bake.
Discard the rest of your starter before feeding, or save it for discard recipes like pancakes and crackers.
Total dough about 850 g. Your starter's own flour and water are already counted in the hydration.
Your starter already holds more flour or water than the recipe needs. Lower the starter amount or raise the total flour.
How to Use the Sourdough Calculator
The calculator has two modes. Feed My Starter works out a feeding by ratio, and Bread Dough builds a full recipe using baker’s percentages.
Feeding your starter
A feeding ratio is written as starter : flour : water. A 1:1:1 feed means equal weights of each, the everyday maintenance feed. A bigger ratio like 1:5:5 gives the starter far more food, so it rises more slowly and is perfect to feed once and leave overnight. Enter how much fed starter you want and the calculator tells you how much to keep, plus the flour and water to add.
Working out a dough
Bakers measure everything as a percentage of the flour, called baker’s percentage. Hydration is the water as a percentage of the flour, so 70% hydration means 700g of water for every 1000g of flour. Salt is usually around 2%. Because your starter is itself made of flour and water, the calculator subtracts what is already in it, so your finished dough lands at exactly the hydration you asked for.
What Hydration Should I Use?
- 60 to 65% - stiff and easy to shape, great for beginners and sandwich loaves.
- 68 to 72% - the classic all-round sourdough, open but still manageable.
- 75 to 80% - a wetter dough with bigger holes that needs a gentler hand.
- 80% and above - focaccia and ciabatta territory, very slack and sticky.
What You’ll Need for Sourdough
The right kit makes sourdough far less fiddly. These are the tools I actually use to bake at home.
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Sourdough Calculator FAQ
What is baker’s percentage?
It is a way of writing a recipe where every ingredient is shown as a percentage of the total flour, and the flour is always 100%. It makes a recipe easy to scale: keep the percentages the same and just change the flour weight.
How much starter should I use in my dough?
Most sourdough loaves use around 20% starter, which is 100g for every 500g of flour. More starter ferments the dough faster, less starter ferments it more slowly. The calculator lets you set any amount and adjusts the rest.
Does the calculator account for the flour and water in my starter?
Yes. In Bread Dough mode it works out how much flour and water your starter already holds, based on its hydration, and subtracts them. The flour and water it tells you to add give the exact hydration you set.
What feeding ratio is best?
For daily upkeep at room temperature, 1:1:1 is fine. If you want to feed once and leave it overnight, use a larger ratio like 1:3:3 or 1:5:5 so the starter does not run out of food and collapse before you get to it.
How do I revive a starter from the fridge?
Take it out, discard most of it, and feed it a couple of times at room temperature until it doubles reliably. The Revive from fridge preset uses a gentle 2:1:1 feed to wake it up. My sourdough starter guide walks through the whole process.