Sourdough Starter Feeding Calculator

How the sourdough starter feeding calculator works

A feeding ratio compares retained starter, fresh flour, and fresh water by weight. In a 1:1:1 feed, 50 g starter receives 50 g flour and 50 g water. In a 1:2:2 feed, the same 50 g starter receives 100 g flour and 100 g water.

The calculator begins with the starter currently in your jar and the amount you want to keep. The difference is shown as discard or starter you can set aside for another use. It then multiplies the retained starter by the flour and water parts of your chosen feed ratio.

The calculator also tracks starter hydration. If the retained starter is not 100% hydration, it is first separated into its existing flour and water. New flour and water are added to those totals, which lets the tool calculate the final hydration after feeding.

What 1:1:1 means for sourdough starter

A 1:1:1 sourdough feeding means equal starter, flour, and water by weight. King Arthur Baking uses equal parts starter, flour, and water by weight as a standard maintenance example. That does not make 1:1:1 the only valid method. It is simply a clear, repeatable ratio.

If you keep 50 g starter, a 1:1:1 feed adds 50 g flour and 50 g water. The jar then contains 150 g total starter. If you keep 100 g starter, the same ratio adds 100 g flour and 100 g water, producing 300 g total.

Ratio notation is about relative amounts, not fixed grams. You can use 10 g, 25 g, 50 g, or another retained amount. The ratio remains the same as long as each part is scaled consistently.

What 1:2:2 and 1:5:5 starter feeds mean

A 1:2:2 feeding gives the starter more fresh flour and water relative to the retained inoculum. With 25 g starter, add 50 g flour and 50 g water. Total starter becomes 125 g.

A 1:5:5 feeding is larger. With 20 g retained starter, add 100 g flour and 100 g water. The resulting starter weighs 220 g. This can be useful when you need to build more starter or want a larger refreshment relative to the amount of mature starter.

Do not assume a bigger ratio has one fixed fermentation time. A larger feed can change how long the starter takes to peak, but room temperature, flour choice, starter condition, water temperature, and microbial activity matter too. Watch the starter rather than treating the ratio as a timer.

How much sourdough starter should you keep?

You only need to maintain as much starter as fits your baking routine. Keeping a huge jar can create unnecessary flour use if you repeatedly discard most of it. A smaller maintained starter can be built up before baking.

The calculator separates current starter from retained starter for this reason. If your jar contains 200 g and you decide to keep 40 g, the tool shows 160 g as discard or set-aside starter. The chosen feed ratio is then applied only to the 40 g you retained.

King Arthur Baking's maintenance guidance provides examples of discarding to a chosen amount and feeding equal flour and water by weight. Your own successful routine can differ. The useful principle is to measure what you retain and what you add so the feeding remains repeatable.

Sourdough discard and starter build calculations

Discard is simply starter you choose not to carry into the next feeding. It is not automatically spoiled. Healthy sourdough discard is often used in recipes that do not rely on it as the only leavening source. If starter shows mold or other signs of contamination, it should not be treated as normal discard.

If you need a specific amount of ripe starter for a bread recipe, you can use the feeding calculator as a build planner. Suppose a recipe needs 200 g starter and you want some left for maintenance. Retain enough mature starter and choose a feeding ratio that produces more than 200 g total.

Plan the amount before feeding to avoid accidental waste. If the calculator shows a final starter amount much larger than you need, reduce the retained starter or use a smaller ratio. If it produces too little, increase the retained amount or feeding ratio.

Starter hydration after feeding

Starter hydration is total water divided by total flour. A 100% hydration starter has equal flour and water by weight. That does not mean the starter is 100% water. It means the water weighs the same as the flour.

If a 100% hydration starter receives equal flour and water, it stays at 100% hydration. If you add more flour than water, the starter becomes stiffer. If you add more water than flour, it becomes more liquid.

The current hydration field matters when the retained starter is already stiff or liquid. For example, 60% hydration starter contains more flour than water. The calculator accounts for that existing composition before it adds the new feed.

For the hydration of the final bread dough, use the Sourdough Hydration Calculator. It includes both the starter and the flour and water added directly to the dough.

Feeding starter by weight instead of cups

Weight is the better unit for starter feeding ratios. Sourdough starter can be full of gas at one moment and stirred flat at another. The same cup can therefore contain very different weights depending on fermentation and handling.

Flour also varies by how it is scooped and packed. A digital kitchen scale removes much of that variation. Put the jar or bowl on the scale, tare it to zero, then weigh the retained starter, flour, and water.

Small feeds benefit from a scale that reads at least to the gram. If you maintain very small starters or use tiny seed amounts, finer resolution can help. The goal is not laboratory precision. It is consistent enough measurement that your ratio means the same thing from one feeding to the next.

How feeding ratio affects fermentation

The feed ratio changes how much fresh food is available relative to the mature starter. A small inoculum with a large flour and water feed starts with fewer mature organisms relative to the new mixture than a 1:1:1 feed.

That relationship can influence the time to visible activity or peak, but it does not determine it alone. Warm temperatures can accelerate fermentation. Cooler temperatures can slow it. Whole grain flour may behave differently from refined flour. Starter health and acidity also matter.

Use the ratio calculator for quantities, not as an exact proofing clock. Record how a particular ratio behaves in your kitchen. If 1:2:2 at your room temperature consistently peaks around the schedule you need, that observation is more useful than a universal time claim.

Feeding starter for a bread or pizza recipe

Build enough ripe starter for the recipe plus the amount you want to keep. If a bread recipe needs 150 g starter and you want 30 g left for maintenance, plan for at least 180 g. A little extra can provide a margin for starter left on the jar or spoon.

Once the starter goes into a bread formula, its flour and water become part of the dough. This matters for true hydration and baker's percentage. The Baker's Percentage Calculator and sourdough hydration tool help analyze those relationships after the feeding stage.

If you are making sourdough pizza, do not enter the whole starter weight as if it were commercial yeast in the Pizza Dough Calculator. First account for the flour and water carried by the starter.

Common sourdough feeding mistakes

Reading 1:1:1 as volume

Feeding ratios are most repeatable when the parts are weights. Equal cups of starter, flour, and water are not equal weights.

Ignoring current starter hydration

If the retained starter is stiff, adding equal flour and water does not instantly make the final mixture exactly the same as starting with a 100% hydration starter.

Keeping too much starter without a reason

A smaller maintained starter can reduce discard and still be built to a larger amount before baking.

Using the calculator as a fermentation timer

The tool calculates mass and hydration. Starter activity still needs observation.

A practical sourdough feeding workflow

1. Weigh the starter in the jar

Know how much mature starter you have before deciding what to retain.

2. Choose how much starter to keep

Keep enough for your maintenance or build plan and set aside the rest.

3. Choose the feed ratio

Use 1:1:1, 1:2:2, 1:5:5, or your own tested ratio.

4. Add the calculated flour and water

Weigh both ingredients rather than estimating by volume.

5. Observe and record the fermentation

Note temperature, flour, feed ratio, and how long the starter takes to become active. Those records turn the calculator's precise quantities into a reliable personal routine.

Questions about feeding sourdough starter