Sourdough Starter Calculator
Find flour and water to feed your starter.
Relative to starter (1 = equal)
Relative to starter (1 = equal)
Results update as you type.
How it works
Feeding a sourdough starter means adding fresh flour and water in proportion to the starter you keep, and this calculator works out the amounts. You enter how much starter you are keeping and the feeding ratio for flour and water relative to that starter, and it returns the grams of flour and water to add plus the total weight after feeding. Sourdough feeding is described by a ratio of starter to flour to water, such as 1:1:1 or 1:2:2. The first number is your existing starter, and the others are how much flour and water to add relative to it. So with 50 grams of starter and a 1:1:1 ratio, you add 50 grams of flour and 50 grams of water, ending with 150 grams total. Higher flour and water ratios, like 1:5:5, feed the starter more and slow its rise, useful for longer gaps between feedings, while lower ratios ferment faster. Keeping equal weights of flour and water gives a 100 percent hydration starter, the most common style. Getting the feed right keeps your starter healthy, active, and ready to leaven bread, and measuring by weight in grams is far more reliable than by volume. Discard any starter beyond what you keep, or use it in recipes. Enter your starter amount and feeding ratio to compute the flour and water to add.
Flour = starter × flour ratio; Water = starter × water ratio
A sourdough feeding ratio is written as starter to flour to water. The calculator multiplies the amount of starter you keep by the flour ratio to get the flour to add and by the water ratio to get the water. A 1:1:1 feeding adds equal weights of flour and water to the starter. The total is the sum of all three.
Source:Baking reference
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter starter to keep.
- 2
Adjust the options
Adjust flour ratio and water ratio if they apply — sensible defaults are already set.
- 3
Read your result
Flour to add updates instantly as you type — no button to press.
Frequently asked questions
How much flour and water do I feed my starter?
Multiply the amount of starter you keep by the flour and water ratios. At a 1:1:1 ratio with 50 grams of starter, you add 50 grams of flour and 50 grams of water. The calculator computes the amounts and the total starter weight from your starter amount and chosen ratios.
What does a 1:1:1 ratio mean?
A 1:1:1 ratio means equal parts starter, flour, and water by weight. If you keep 50 grams of starter, you add 50 grams of flour and 50 grams of water. This is a common, balanced feeding that keeps a 100 percent hydration starter active and is a good default for regular baking.
Should I feed more before a long gap?
Yes. A higher feeding ratio, such as 1:5:5, gives the starter more food relative to its size, so it takes longer to consume it and stays viable longer between feedings. This is useful before travel or if you bake infrequently. A lower ratio ferments faster and suits frequent baking.
Why measure by weight instead of volume?
Flour and starter vary a lot in how much they weigh per cup depending on how they are packed, so measuring by volume is inconsistent. Weighing in grams gives precise, repeatable feedings, which keeps your starter's hydration and behavior predictable. A kitchen scale is the single most helpful tool for reliable sourdough.
What do I do with the discard?
The starter beyond the amount you keep is called discard. You can throw it away, but many bakers use it in recipes like pancakes, crackers, or waffles to avoid waste, since discard still has flavor even though it is less active. Keep discard in the fridge until you are ready to use it.