Sourdough Hydration Calculator: Flour, Water and Starter

How sourdough hydration is calculated

Hydration is total water divided by total flour. With sourdough, part of both sits in the starter, so split the starter into its flour and water first.

Starter flour = starter ÷ (1 + starter hydration) Starter water = starter − starter flour Hydration = (water + starter water) ÷ (flour + starter flour)

Example. 500 g flour, 350 g water and 100 g of a 100% starter. The starter adds 50 g of flour and 50 g of water, so the dough is 400 g of water over 550 g of flour: 72.7% hydration, not the 70% the flour and water alone suggest.

Building a recipe from hydration

Working backwards, the dough weight is the total flour times one plus the hydration and salt percentages. Find the total flour, take the starter's share out of it, and the rest follows.

Total flour = dough ÷ (1 + hydration + salt %) Starter = total flour × starter % Flour to add = total flour − starter flour Water to add = total flour × hydration − starter water

A 900 g loaf at 75% hydration with 20% starter and 2% salt needs 458 g flour, 331 g water, 102 g starter and 10 g salt.

Hydration guide

Hydration	Dough	Good for
55–65%	Firm, easy to shape	Bagels, sandwich loaves, beginners
65–75%	Soft, slightly sticky	Most free-form sourdough loaves
75–85%	Wet, needs strength	Open crumb, ciabatta-style bread

These ranges assume white bread flour. Whole wheat and rye absorb more water, so the same dough feel comes at a higher number.

Questions

What is hydration in sourdough?

Hydration is the weight of water divided by the weight of flour, as a percentage. 750 g of water to 1,000 g of flour is 75% hydration. Higher hydration gives a wetter dough and usually a more open crumb.

Does the starter count toward hydration?

Yes. A starter is part flour and part water, so both belong in the totals. A 100% hydration starter is half flour and half water by weight. Leaving it out makes the dough look stiffer on paper than it is.

How do I calculate the hydration of my dough?

Add the flour in the starter to the recipe flour, and the water in the starter to the recipe water, then divide total water by total flour. 500 g flour, 350 g water and 100 g of 100% starter is 400 g water over 550 g flour, about 72.7%.

What hydration should I use for sourdough?

Around 70% to 75% is a common starting point for a free-form loaf with bread flour. Lower hydrations are easier to shape, and higher ones give a more open crumb but a stickier dough. Whole wheat flour absorbs more water, so it handles a higher hydration.

How much starter should I use?

Many recipes use starter equal to 10% to 20% of the flour weight. More starter ferments faster, and less gives a longer, slower rise, which helps on warm days.