The Complete Sourdough Hydration Guide

Hydration is the single number that decides the character of your bread. It sets the crumb and crust, the shape you can build, the folds you need, and how long fermentation takes. This guide explains what hydration means, how to calculate it correctly including the starter that many recipes leave out, and how to pick the right level for your next loaf.

What hydration actually means

Hydration is the weight of water divided by the weight of flour, written as a percentage. A 70% dough has 70 g of water for every 100 g of flour.

Why bakers use percentages: percentages describe the character of a dough, not its size. When a recipe says 75% hydration and 2% salt, it means the same bread whether you use 500 g of flour or 5 kg. You can scale it up or down, and the percentages stay fixed. That is the core idea of baker’s math, and why almost every serious sourdough formula you meet is written this way.

The formula

True hydration = (total water divided by total flour) times 100

The word total is where people slip. Most recipes list only the water you pour in and the flour you scoop out. But if you use a starter, you are already adding flour and water without measuring it.

• A starter at 100% hydration is half flour and half water by weight.
• A starter at 200% hydration, sometimes called a liquid starter, is one third flour and two thirds water.

Worked example: the starter that adds 2.7 points

Take a common formula: 500 g flour, 350 g water, 100 g starter at 100% hydration, and 10 g salt.

• Flour inside starter: 100 g times 50% = 50 g
• Water inside starter: 100 g times 50% = 50 g
• Total flour: 500 + 50 = 550 g
• Total water: 350 + 50 = 400 g
• True hydration: 400 divided by 550 times 100 = 72.7%

The recipe says 70% based on 350 divided by 500, but the dough is really 72.7%. That is not a rounding error. It is a 2.7 point shift in gluten hydration, fermentation speed and crumb. This is exactly what the sourdough hydration calculator does for you, and you can check your starter amounts with the starter feeding calculator.

What each hydration level does

Each level has its own page with handling tips: 70%, 75%, 80%, 85% and 90%. For a quick overview, see the hydration levels chart.

How to pick your hydration

Three things matter most:

1. Your flour. Strong bread flour at 12 to 13% protein handles 75 to 80% happily. Whole wheat and rye soak up even more water but build weaker gluten, so 65 to 72% is usually smarter there. Weak all purpose flour often starts to tear around 75%.

2. Your skill. Hydration and difficulty rise together. At 70% you can shape confidently. At 85% the dough is soft and needs wet hands and practice. Move up in five point steps, one bake at a time.

3. Your bread. A sandwich loaf suits 65 to 70%. A country loaf with an open crumb suits 75 to 80%. Focaccia suits 85 to 95%. Pick the bread first, then pick the number.

How to change a recipe’s hydration

The math is simple. For every 100 g of total flour, each hydration point is 1 g of water.

• To go from 70% to 75% on a 500 g flour loaf: add 5 times 5 g = 25 g water.
• To go from 75% to 70%: take away 25 g.

Use the tweak slider on the calculator. It does this for you, including the hidden water in the starter.

Two practical tips when you raise hydration:

• Add water in stages. Mix most of the water with the flour first, then add the rest during the first folds. Dough takes water more easily once gluten has relaxed.
• Watch the dough, not the clock. Wetter doughs often ferment a little faster. Look for a puffy, domed, jiggly dough that has grown 50 to 75% before you shape.

Three mistakes beginners make

1. Trusting the recipe number. Starter inclusive hydration is usually higher than the number on the page. Use true hydration when you compare recipes or copy a formula. The recipe scaler keeps true hydration fixed when you scale.

2. Judging wetness by stickiness alone. A 70% dough can feel sticky at the start of mixing and smooth by the end of bulk. Stickiness early on is often about fermentation, not water. Judge the dough after folds, not at the first mix.

3. Chasing high hydration too early. Photos of 85% loaves with huge holes look exciting, but those breads come from strong flour, a mature starter, and a lot of practice. A well made 70% loaf beats a collapsed 85% loaf every time.

Hydration and fermentation

Water moves fermentation faster. A wetter dough ferments more quickly because enzymes and yeast move more freely, so an 80% dough can overproof in the time a 65% dough takes to double. If you raise hydration, shorten bulk a little and watch for the signs: a puffy domed dough that jiggles and has grown 50 to 75% is ready to shape. When in doubt, shape a bit early. An underproofed loaf is still good and fixable. An overproofed loaf tends to stay flat.

What to do next

Choose your bread, pick a percentage, weigh everything in grams, and let the calculator handle the starter math. Try baking the same recipe at 70% and then at 75% and you will feel what the percentage means faster than any article can explain.

To keep your starter ready for that bake, see the sourdough starter guide for feeding ratios and fridge routines. When a bake does not go as planned, the troubleshooting FAQ has practical fixes.