Does this calculator assume a 100% hydration starter?

Yes. It treats the starter as half flour and half water by weight. If your starter is stiffer or more liquid, you can still use the outputs as a starting point and then manually adjust water or flour a little to match your usual dough feel.

Is salt included in any of these calculations?

No. The calculator focuses on flour, starter, and water only. Salt is usually 1.8–2.5% of flour weight and should be added separately according to your recipe or taste.

What exactly does starter % mean in this context?

Starter percentage is the weight of starter divided by the weight of base flour, expressed as a percentage. For example, 20% starter on 500 g flour means 100 g of starter in the dough. Higher percentages typically speed up fermentation.

Can I use this calculator for preferments or levain builds?

Yes. Treat the starter output as the levain build that will be mixed into your final dough. You can design the levain formula using these numbers and then fold it into the main dough at mix time.

How do I scale the recipe for multiple loaves?

Enter the total flour weight needed for all loaves combined. The starter and water outputs scale linearly, so doubling flour doubles starter and water as well.

Why does my real dough sometimes feel wetter or drier than the hydration suggests?

Flour type, age, protein content, whole grain percentage, and room conditions all affect how much water dough will absorb. Use the hydration number as a precise reference, but expect to fine‑tune based on feel and experience.

cooking calculator

Sourdough Starter Ratio Calculator

Calculate starter and water amounts for a target hydration and inoculation.

Results

Starter needed (g): 100.00
Water to add (g): 500.00
Total dough weight (g): 1100.00
Actual hydration: 100.00%

Overview

This sourdough starter ratio calculator helps you turn baker’s percentages into actual gram amounts for your dough. By combining flour weight, starter percentage (inoculation), and target hydration, it tells you exactly how much 100% hydration starter and extra water to use so your dough feels the way you expect, batch after batch.

How to use this calculator

Decide how much flour you want in your final dough (excluding the flour already in your starter) and enter that as Flour weight in grams.
Choose a starter percentage (inoculation level) relative to the flour—common values range from 10–30% depending on how fast you want fermentation to run.
Set your target hydration percentage based on how wet you like the dough. Lower hydrations (60–68%) are typical for sandwich loaves; higher hydrations (70–85%+) are common for open-crumb boules and batards.
Review the outputs for Starter needed (g), Water to add (g), Total dough weight (g), and Actual hydration.
Adjust starter percentage or hydration up or down and rerun the calculation to see how those changes affect water and total dough size before you start mixing.

Inputs explained

Flour weight (g): The amount of flour, in grams, that goes into your final dough formula, not counting the flour already in your starter. If you want two 500 g loaves, you might start with 700–800 g of flour, depending on hydration and shaping loss.
Starter % of flour: The inoculation level: starter weight divided by flour weight, expressed as a percentage. A higher starter percentage usually shortens bulk fermentation and proof times, while a lower percentage slows things down and can produce a different flavor profile.
Target hydration %: Total water as a percentage of total flour (flour in the dough plus flour in the starter). For example, 75% hydration means total water weight is 0.75 × total flour weight. Hydration strongly affects dough strength, extensibility, and crumb openness.

Outputs explained

Starter needed (g): The total weight of 100% hydration starter to add to your dough, based on your chosen starter percentage. Half of this weight is flour and half is water.
Water to add (g): The additional water you need to pour into the bowl so that total water (starter water plus added water) matches your target hydration level for the flour in the system.
Total dough weight (g): An approximate total mass of your mixed dough, equal to base flour + starter + added water. This is useful for deciding how many loaves, rolls, or baguettes you can shape from a batch.
Actual hydration: The calculated hydration after accounting for the flour and water inside the starter and the water you add. It should be very close to your target hydration when using a 100% hydration starter.

How it works

The calculator assumes your sourdough starter is at 100% hydration, meaning it contains equal parts flour and water by weight. If your starter is stiffer or looser, you can still use the tool as a baseline and then tweak water or flour a bit by hand.

You choose a total flour weight for the dough (excluding the flour already inside the starter) and a starter percentage relative to that flour. For example, 20% starter on 500 g flour means 100 g of starter will go into the mix.

Given a 100% hydration starter, half of that starter weight is flour and half is water. The calculator splits the starter into starter flour and starter water so it can track your total flour and total water correctly.

Next, it converts your target hydration percentage into a decimal (for example, 75% becomes 0.75) and applies it to the total flour in the system: all base flour plus the flour inside the starter. Target water = Target hydration × (Base flour + Starter flour).

Because the starter already contributes some water, the tool subtracts the starter water from the target water amount to find how much extra water you need to add to the bowl. This is reported as Water to add.

Finally, it computes total dough weight by adding base flour, starter, and added water together, and it reports the actual hydration that results from these numbers so you can confirm things line up with your expectations.

Formula

Assume a 100% hydration starter (50% flour, 50% water by weight).\n\nLet F = base flour weight (g)\nLet s = starter percentage (as a decimal, e.g., 0.20 for 20%)\nLet H = target hydration (as a decimal, e.g., 0.75 for 75%)\n\nStarter weight S = F × s\nStarter flour = S ÷ 2\nStarter water = S ÷ 2\nTotal flour = F + Starter flour\nTarget total water = H × Total flour\nWater to add = Target total water − Starter water\nTotal dough weight ≈ F + S + Water to add\nActual hydration = (Starter water + Water to add) ÷ Total flour

When to use it

Scaling a favorite sourdough recipe up or down while keeping hydration and inoculation consistent so the dough handles similarly in different batch sizes.
Experimenting with faster or slower fermentation by adjusting starter percentage while holding hydration constant, helping you match dough timing to your schedule.
Designing a new formula from scratch—choosing flour weight, starter percentage, and hydration first, then letting the calculator tell you how much starter and water to weigh out.
Planning multi-loaf bakes where you want a very specific total dough weight per loaf (for example, 900 g batards or 500 g boules) and need to work backward from those targets.
Checking recipe conversions when switching from instant yeast breads to sourdough versions that use a levain or starter build instead of commercial yeast.

Tips & cautions

Keep a small notebook of hydrations that work well with your flours and shaping style. Use the calculator to hit those hydrations precisely every time instead of guessing by feel alone.
If your starter is not exactly 100% hydration (for example, a stiff 60% starter or a more liquid 125% starter), you can still use the tool as a starting point and then nudge the added water up or down a bit to match your usual mixing experience.
Remember that whole grain flours (like whole wheat or rye) absorb more water than white bread flour. You may prefer higher target hydrations when working with high whole grain percentages.
Salt is typically 1.8–2.5% of flour weight and is not included in this calculator. Add salt separately after the initial mix or during an autolyse step, depending on your process.
If you add high-moisture mix-ins (like pumpkin puree, olives, soaked grains, or mashed potatoes), treat some of that moisture as part of your hydration and consider trimming the added water slightly.
The model assumes a 100% hydration starter. If your starter hydration is significantly different and you do not adjust water or flour manually, actual hydration may drift away from the target.
It tracks only flour, starter, and water. Salt, sugar, fats, and mix-ins are not included in the gram totals and must be added separately in your formula.
Fermentation timing still depends on temperature, flour strength, starter health, and dough handling. Matching starter percentage and hydration does not guarantee identical proof times in different kitchens.
Hydration preferences are personal and flour-specific. Use the calculator as a precision tool, but ultimately judge dough by feel and behavior as you gain experience.

Worked examples

Example 1: 500 g flour, 20% starter, 75% hydration

Base flour F = 500 g; starter percentage s = 20% = 0.20; target hydration H = 75% = 0.75.
Starter weight S = 500 × 0.20 = 100 g.
Starter flour = 100 ÷ 2 = 50 g; starter water = 50 g.
Total flour = 500 + 50 = 550 g.
Target total water = 0.75 × 550 = 412.5 g.
Water to add = 412.5 − 50 ≈ 362.5 g (the calculator will show a rounded value).
Total dough weight ≈ 500 + 100 + 362.5 ≈ 962.5 g, with an actual hydration close to 75%.

Example 2: 300 g flour, 15% starter, 80% hydration (small test loaf)

Base flour F = 300 g; s = 15% = 0.15; H = 80% = 0.80.
Starter weight S = 300 × 0.15 = 45 g.
Starter flour = 22.5 g; starter water = 22.5 g.
Total flour = 300 + 22.5 = 322.5 g.
Target total water = 0.80 × 322.5 = 258 g.
Water to add = 258 − 22.5 ≈ 235.5 g.
Total dough weight ≈ 300 + 45 + 235.5 ≈ 580.5 g—perfect for a single small loaf.

Example 3: Two boules at ~900 g each with 70% hydration

You want about 1,800 g of total dough for two ~900 g loaves at 70% hydration with 25% starter.
Start by guessing a flour weight—for example, F = 1,050 g; s = 25% = 0.25; H = 70% = 0.70.
Run the calculator: it returns starter needed, water to add, and total dough weight.
If the total dough weight is slightly high or low, tweak F up or down and rerun until the total sits close to 1,800 g while keeping hydration and starter percentage where you want them.

Deep dive

Use this sourdough starter ratio calculator to convert baker’s percentages into exact gram amounts for your starter, water, and total dough. Enter flour weight, starter percentage, and target hydration and it will compute starter needed, water to add, total dough weight, and actual hydration.

It is ideal for home bakers and small artisan bakeries who want consistent dough feel and fermentation across different batch sizes and schedules. The calculator assumes a 100% hydration starter, making it easy to plug into most modern sourdough formulas.

FAQs

Does this calculator assume a 100% hydration starter?: Yes. It treats the starter as half flour and half water by weight. If your starter is stiffer or more liquid, you can still use the outputs as a starting point and then manually adjust water or flour a little to match your usual dough feel.
Is salt included in any of these calculations?: No. The calculator focuses on flour, starter, and water only. Salt is usually 1.8–2.5% of flour weight and should be added separately according to your recipe or taste.
What exactly does starter % mean in this context?: Starter percentage is the weight of starter divided by the weight of base flour, expressed as a percentage. For example, 20% starter on 500 g flour means 100 g of starter in the dough. Higher percentages typically speed up fermentation.
Can I use this calculator for preferments or levain builds?: Yes. Treat the starter output as the levain build that will be mixed into your final dough. You can design the levain formula using these numbers and then fold it into the main dough at mix time.
How do I scale the recipe for multiple loaves?: Enter the total flour weight needed for all loaves combined. The starter and water outputs scale linearly, so doubling flour doubles starter and water as well.
Why does my real dough sometimes feel wetter or drier than the hydration suggests?: Flour type, age, protein content, whole grain percentage, and room conditions all affect how much water dough will absorb. Use the hydration number as a precise reference, but expect to fine‑tune based on feel and experience.

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This sourdough starter ratio calculator is a planning aid for flour, starter, and water amounts based on simplified hydration assumptions. It does not account for all factors that influence dough behavior, such as flour strength, temperature, or starter hydration outside 100%. Always rely on your senses and adjust formulas as needed for your specific ingredients and kitchen conditions.