Sourdough Hydration Calculator (Including Starter)

What hydration includes

Sourdough hydration is total water divided by total flour, multiplied by one hundred. The important word is total: a starter carries both ingredients into the mixing bowl. If you count the water you pour in but ignore the starter’s flour, your result describes only part of the dough. This calculator separates those contributions and reports the water needed for a chosen target. All ingredient amounts are weights in grams, including the starter. Cups are unsuitable for this calculation because water and flour have very different weights per cup.

The model is intended for a lean dough made with flour, water, starter and salt. It does not estimate water hidden in eggs, butter, milk, fruit or cooked grain soakers. A recipe containing those ingredients needs its own accounting convention. Keep that convention consistent when comparing batches. A hydration number is useful for describing a formula, but it is not a promise of an open crumb, a particular fermentation time or an easy shaping experience.

Don’t eat raw dough or batter; raw flour and eggs can carry bacteria. See the FDA flour safety guidance.

How to use the calculator

Enter the flour and water added directly to the final dough, excluding anything already inside the starter. Then enter the starter weight and its hydration. A starter fed equal weights of flour and water is nominally 100% hydration, while a stiff starter may be 50% or 60%. Use the actual maintenance formula rather than guessing from how thick the starter looks. Flour type and fermentation can change its appearance without changing the original flour-to-water ratio.

Choose a target hydration and a salt percentage based on total flour. The result shows total flour, total water, current hydration, target added water and salt grams. Target added water replaces the water input; it is not an extra amount to pour on top. The difference tells you how far the current water entry is from that target. A negative target water result means the starter already contains more water than the chosen formula allows, so the starter amount or target must change.

The calculation, step by step

Divide starter hydration by one hundred to express it as a ratio, called r. Starter flour equals starter weight divided by one plus r. Starter water equals starter weight minus starter flour. Add the starter flour to the flour in the final mix and do the same for water. Divide the resulting total water by total flour to get hydration. This also explains why a 200 g starter does not necessarily contribute 100 g of each ingredient: that split applies only at 100% hydration.

For target water, multiply total flour by the target percentage divided by one hundred. Subtract starter water from that total to find the amount to add directly. Salt is total flour multiplied by the selected salt percentage divided by one hundred. This salt calculation treats starter as unsalted. If your preferment contains salt, account for that salt separately before weighing the final addition. Salt percentage is a formula choice, not a requirement of the hydration equation.

Worked example: equal-weight starter

Suppose the final mix contains 500 g flour, 350 g water and 100 g starter at 100% hydration. The starter contributes 50 g flour and 50 g water. Total flour is therefore 550 g and total water is 400 g. Dividing 400 by 550 gives approximately 72.7% hydration. Calling this a 70% dough from the direct additions alone would miss the starter’s effect. That difference matters when you compare this batch with another recipe using less starter.

To make the same flour and starter combination at 70% hydration, total water should be 385 g. Subtract the starter’s 50 g water and add 335 g directly, which is 15 g less than the original 350 g. At 2% salt, weigh 11 g salt because the denominator is 550 g total flour. The final dough would weigh 946 g before any handling loss: 500 plus 335 plus 100 plus 11.

Worked example: a stiff starter

Now use 600 g added flour, 390 g added water and 150 g starter at 50% hydration. The starter contains 100 g flour and 50 g water because 150 divided by 1.5 is 100. Total flour is 700 g and total water is 440 g, giving approximately 62.9% hydration. The same starter weight at a different hydration would give a different result, even though the number on the starter scale remained unchanged.

For a target of 68%, total water becomes 476 g. Remove the starter’s 50 g contribution from that figure and the direct water addition is 426 g. That is 36 g more than the first version. At 2% salt, the salt amount is 14 g. Write the revised formula in full before mixing so the target water does not get mistaken for an additional correction after the original water has already gone into the bowl.

Choosing a useful starting range

The table gives approximate planning bands for familiar bread styles, not definitions or tested formulas. Flour strength, whole-grain content, shaping method and the baker’s handling preferences all affect a workable range. Begin with a recipe developed for the flour you have. A manageable dough that you can shape consistently is more useful than a higher hydration number chosen simply because it sounds advanced. More water can require changes to mixing, folding and handling.

Whole-grain flour can absorb water differently from white flour, and two bags labeled bread flour can behave differently. Humidity and flour storage also influence the feel of a dough. Add any reserved water deliberately and record the final amount. If you hold back 20 g at mixing and later add only 10 g, the final hydration calculation should include the 10 g actually used, not the full planned reserve.

Starter quantity and fermentation are separate choices

Hydration describes composition; it does not describe how mature or active your starter is. Two doughs with the same hydration can ferment at different rates because they contain different amounts of prefermented flour or begin at different temperatures. Use the sourdough starter calculator to plan a build, then use this page to account for the flour and water transferred from that build into the dough. Do not count the flour left behind in the starter jar.

When increasing starter quantity, recalculate direct flour and water if you want to keep the overall formula unchanged. Otherwise you may unintentionally increase both dough weight and hydration. A useful notebook records starter weight, starter hydration, total flour, total water and final dough temperature together. Those entries make a later comparison much clearer than a note that says only “more starter this time.”

Troubleshooting sticky or stiff dough

Before changing water, check measurement and process. A dough may feel sticky early in mixing but become more organized after the recipe’s rest or folds. Adding flour repeatedly to the bench can reduce the final hydration by an unknown amount. Instead, use the handling method recommended by your recipe and weigh any deliberate flour addition. If the dough consistently needs adjustment, update the written formula for the next batch rather than relying on an unrecorded handful.

If you are converting a pizza formula or a pan loaf, retain that recipe’s shaping and fermentation instructions. Hydration alone does not make a rustic loaf formula suitable for pizza or a sandwich tin. The linked baker’s percentage calculator helps compare the complete ingredient ratios, while the pizza calculator addresses dough quantity for a particular number of pizzas. Use this tool for the narrower question it answers: how much flour and water are actually in your sourdough.

Frequently asked questions

Related tools and guides

• Sourdough starter calculator
• Bakers percentage calculator
• Pizza dough calculator