Ingredient·Calculator

№01 · Sourdough workbench · Grams only

Sourdough starter feeding calculator

By Michael, independent developer at IngredientCalculator (about). Method documented . Updated .

Calculate seed, flour and water for one feed, or plan two to four linked feeds. Include the starter you want to keep and track its flour and water.

Plan your feed

1. What you are planning
2. Amounts to plan for

Optional extra for starter left on the jar or the spatula. Enter 0 if you do not need it. Your planned mix is recipe + keep + allowance.

3. Feeding ratio by mass

The order is seed : flour : water, all by mass. Presets and starting values are examples, not a feeding schedule.

4. Seed hydration for the audit

Example default of 100% means equal weights of flour and water in the seed. Use your own starter's figure if you know it. The audit assumes a starter of just flour and water (King Arthur Baking).

Your mixing plan

Weigh these amounts

Calculate a feed to see your quantities and hydration audit.

Mixing amounts only. The tool doesn’t predict when a starter will be ripe, how it will behave, or how much you will recover after fermentation. Rounded display values can differ slightly from the total.

Feeding ratios and the seed hydration audit

Type your feeding ratio and get the seed starter, flour and water to weigh, in grams. Work backward from the ripe starter a recipe needs plus the amount you want to keep, or forward from the seed already in your jar. A 1:1:1 feed is equal parts by weight of existing starter, added flour, and added water, and King Arthur Baking calls it a good place to start while noting that some bakers prefer different ratios (King Arthur Baking).

Custom ratio parts from 0.001 to 10,000 are supported. For a sequence of feeds, use the linked planner below.

The hydration audit counts what is already in your seed. Your seed already holds flour and water, and King Arthur Baking says the flour and water in a starter or preferment should be counted when you figure hydration (King Arthur Baking on hydration). So a feed with equal new flour and water doesn’t land on 100% hydration unless the seed is already there. The audit below shows the flour, the water and the resulting percentage side by side.

№02 · Linked feedings

Build your starter through two to four feeds

Set a separate ratio for each feed. This planner works backward from your final amount, then carries the calculated flour and water forward from your starting seed.

Use every gram from one feed as the seed for the next. Take the recipe amount, reserve and allowance only after the final feed. The model carries mass and flour/water components unchanged between feeds, with no fermentation losses. It does not predict timing, readiness or culture strength.

Final recipe + keep + allowance must total more than zero and no more than 1,000,000 g. Each ratio part and initial hydration can be 0.001 to 10,000.

Complete the linked plan to see the starting seed and each feed.

How linked sizing works
For each feed with seed : flour : water = a : b : c,
growth factor = (a + b + c) ÷ a.
Initial seed = final target ÷ product of all growth factors.
At each feed, new flour = carried seed × b ÷ a; new water = carried seed × c ÷ a.
Carry all mixed mass and both flour/water components forward.
Hydration = total water ÷ total flour × 100.

№03 · Method

How the math works

Target mode starts from what you need. The amount of starter a recipe calls for varies from recipe to recipe, and a good build leaves you enough for the recipe plus enough left over to keep feeding and maintaining the jar (King Arthur Baking). Add those two, plus any allowance for what clings to the jar, and split the total across your ratio.

Target mode
T = recipe + keep + allowance
For ratio a:b:c, seed = T × a ÷ (a + b + c)
New flour = T × b ÷ (a + b + c)
New water = T × c ÷ (a + b + c)

Seed mode
New flour = seed × b ÷ a
New water = seed × c ÷ a
Total = seed + new flour + new water

Why your seed's hydration changes the answer

Your seed carries its own flour and water into the mix, and both count toward hydration (King Arthur Baking). Split the seed first, then add what you’re pouring in.

Let h = seed hydration ÷ 100.
Flour in seed = seed ÷ (1 + h)
Water in seed = seed − flour in seed
Final hydration = 100 × (water in seed + new water) ÷ (flour in seed + new flour)
Source examples and hydration context

Both modes are mass balances. Nothing evaporates in the arithmetic, so the mixed total is the seed plus what you add. King Arthur Baking's own worked feed shows the same accounting, where 100 grams starter + 100 grams flour + 100 grams water = 300 grams starter, and a smaller seed of 50 grams with 125 grams flour and 125 grams water also reaches 300 grams (King Arthur Baking). Both land on the same total from different seeds, which is exactly what target mode solves for you.

The guide's by-mass feeding adds 113g flour and 113g water to 113g of starter, and after you take what a recipe needs it says to feed the reserved starter with 113g flour and 113g water (King Arthur Baking). Keeping a portion back matters for a plain reason. Feed everything and never take any out, and you end up with a very large container of starter (King Arthur Baking).

Hydration is the weight of the water divided by the weight of the flour, written as a percentage, so 750g of water with 1,000g of flour is 75% (King Arthur Baking). Equal weights of flour and water give 100% (King Arthur Baking). A starter gets measured the same way, with its flour treated as 100% (King Arthur Baking).

Run a stiff seed through that and the gap shows up fast. A starter with twice as much flour as water by weight sits at 50% hydration (King Arthur Baking), so feeding it equal new flour and water still leaves the mix short of the equal-weights case. Switch the seed hydration field between a liquid and a stiff figure and watch the audit move. King Arthur Baking's own bread example counts the flour and water inside the preferment to reach about 77% hydration from 425g water over 550g flour (King Arthur Baking).

One limit worth stating plainly. The audit is a snapshot at mixing time, it assumes a starter of just flour and water (King Arthur Baking), and it assumes the hydration figure you entered is right. Fermentation is not modelled here at all.

№04 · Worked examples

The same feed, four ways

These four examples show the inputs and resulting masses. Enter the same values in the single-feed calculator to follow the calculation.

Recipe plus what you keep

The same target with a stiff seed

A small seed, a big build

An uneven ratio

Sample inputs above are examples chosen to show the arithmetic, not recommendations for your starter.

№05 · Sources

Where these numbers come from

Calculation method and attribution

Two kinds of numbers appear on this page, and they come from different places. The quantities in the calculator, the table and the examples are computed in code from the masses and ratios you enter, never looked up or estimated. The baking definitions are attributed to King Arthur Baking and linked next to each claim.

The method section shows the mass and hydration formulas. For linked feeds, the component ledger separates flour and water already in the seed from each new addition, so you can follow the calculation.

IngredientCalculator is built by Michael, an independent developer who builds small, fast cooking tools (about page), with a GitHub profile at github.com/theluckystrike. No kitchen trial of these ratios is claimed, and nothing here is a food safety or fermentation judgment.

№06 · Before you mix

Using the calculator

Does a 1:2:2 feed give me a 100% hydration starter

Only if your seed is already at 100%. Equal weights of flour and water are what make 100% hydration (King Arthur Baking), and the flour and water inside the seed count toward the total (King Arthur Baking). Feed a stiff seed the same way and the audit lands lower.

How much starter should I keep back

Enough to carry on with. The amount a recipe calls for varies from recipe to recipe, and a build should leave enough starter left over so that you can continue to feed and maintain it (King Arthur Baking). Put that figure in the keep field and target mode sizes the feed around it.

Which feeding ratio is correct

A ratio is an arithmetic choice, not a rule this page can settle for you. King Arthur Baking treats 1:1:1 as a good place to start and notes that some bakers prefer different ratios (King Arthur Baking). Pick the one your routine already uses and let the calculator do the weighing math.

What counts as a liquid or a stiff starter

Hydration tells you. Liquid starters are generally in the 100-125% range and stiff starters generally in the 50-65% range (King Arthur Baking). A stiff starter feed given by King Arthur Baking is 1 part starter, 1 part water, 2 parts flour (King Arthur Baking). In the calculator’s seed:flour:water order, enter this as 1:2:1.

Why the tool asks for grams and not cups

Feeding ratios here are ratios by weight. King Arthur Baking's feedings are given as equal parts by weight of starter, flour and water (King Arthur Baking), and weight is what the arithmetic needs. No cup densities are used anywhere on this page.

№07 · Related tools

Sourdough hydration calculator
Carry this starter's flour and water into the hydration of the finished dough.

Baker's percentage calculator
Express the rest of a dough against the total flour weight.

These are mixing quantities calculated from your entered masses and ratios. The result assumes only flour and water, with no fermentation loss included.