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Generated on: July 20, 2026 at 09:33 PM

Sourdough Starter Calculator

Inputs

Starter to keep50 g
Flour & water ratio5
Hydration100 %

This is a guide based on the ratio and hydration you enter. Real starters vary with flour type, temperature, and ripeness; adjust feeding frequency and amounts to suit how your culture behaves.

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Food & Cooking

Sourdough Starter Calculator

Work out how much flour and water to add when feeding a sourdough starter at a chosen feeding ratio and hydration.

Inputs

≥ 0 g
≥ 0
%

Results

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Details

Feeding 50 g of starter at a 1:5:5 ratio needs ... of flour and ... of water, for ... of refreshed starter.

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Sourdough Starter

Feeding a sourdough starter means refreshing a small amount of the existing, ripe culture with fresh flour and water. The amounts are usually described as a ratio and a hydration. This calculator turns that ratio and hydration into the exact weights of flour and water to add for whatever amount of starter you choose to keep.

The 1:X:X feeding ratio

A feed is written as three numbers — for example 1:5:5. They are proportions, by weight, of existing starter to fresh flour to water. The first number is always 1, so the flour and water are scaled from the amount of starter you keep:

flour=starter×X\begin{aligned} \text{flour} &= \text{starter} \times X \end{aligned}

A larger ratio dilutes the old culture more. A 1:1:1 feed barely refreshes it and ferments fast, while a 1:10:10 feed slows things down and buys a longer gap before the next feed.

Hydration sets the water

Hydration is the weight of water as a percentage of the flour — not of the whole mixture. Once the flour is fixed by the ratio, the hydration sets the water:

water=flour×hydration100\begin{aligned} \text{water} &= \text{flour} \times \frac{\text{hydration}}{100} \end{aligned}

At 100% hydration the water and flour weights are equal, giving a thick but pourable starter. A stiff starter at 50% hydration uses half as much water as flour and ferments more slowly. The total refreshed starter is simply the three parts added together:

total=starter+flour+water\begin{aligned} \text{total} &= \text{starter} + \text{flour} + \text{water} \end{aligned}

Worked example

Keep 50 g of starter and feed it at 1:5:5 with 100% hydration:

flour=50×5=250 gwater=250×100100=250 gtotal=50+250+250=550 g\begin{aligned} \text{flour} &= 50 \times 5 = 250 \text{ g} \\ \text{water} &= 250 \times \frac{100}{100} = 250 \text{ g} \\ \text{total} &= 50 + 250 + 250 = 550 \text{ g} \end{aligned}

So you add 250 g of flour and 250 g of water to 50 g of starter, ending with 550 g of refreshed culture.

The discard

Each feed keeps only a small portion of the previous starter, so the rest is removed before feeding — that removed portion is the discard. It is fully usable: stir it into pancakes, waffles, crackers, or flatbreads, or save a jar in the fridge to bake with later. Discarding keeps the total manageable and the culture lively rather than overgrown.

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Frequently Asked Questions (FAQ)

What does a 1:5:5 feeding ratio mean?

The three numbers are the proportions, by weight, of existing starter to fresh flour to water. A 1:5:5 feed means for every 1 part of old starter you add 5 parts flour and 5 parts water. So 50 g of starter takes 250 g of flour and 250 g of water. A larger ratio (such as 1:10:10) dilutes the culture more, which slows fermentation and is handy when you want a longer gap before the next feed.

What does hydration percentage mean?

Hydration is the weight of water expressed as a percentage of the flour, not of the whole mixture. At 100% hydration the water and flour weights are equal, giving a thick but pourable batter. A stiff starter at 50% hydration uses half as much water as flour and behaves more like a dough; it ferments and sours more slowly, which suits longer storage. The ratio sets how much flour you add; the hydration sets how much water goes with it.

Why is there leftover starter, and what do I do with it?

Each feed only keeps a small amount of the old starter and refreshes it with new flour and water, so the rest is removed first. That removed portion is the discard. It is perfectly usable: stir it into pancakes, waffles, crackers, or flatbreads, or keep a jar of it in the fridge to bake with later. Discarding keeps the total volume manageable and the culture vigorous rather than overgrown and sluggish.

Disclaimer

This is a guide based on the ratio and hydration you enter. Real starters vary with flour type, temperature, and ripeness; adjust feeding frequency and amounts to suit how your culture behaves.

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