Baker’s Math Explained: How to Design Your Own Sourdough Recipes

The first time someone explained baker’s percentages to me, I nodded politely—and understood almost nothing.

There were numbers. Percent signs. Formulas written like equations. And somehow, everyone else seemed to get it instantly.

But here’s the truth most beginner bakers don’t hear often enough: Baker’s math isn’t about math. It’s about giving structure to what your dough is already doing.

Once you see it that way, baker’s percentages stop being intimidating. They become one of the most useful tools you can have in your kitchen.

Why We Weigh Flour (And Ignore Cups)

Cups feel comfortable. They’re what most of us grew up using. But flour doesn’t behave politely in cups.

Depending on how you scoop:

• A cup of flour can weigh 110 grams.
• Or 150 grams.
• Or anywhere in between.

That difference alone can completely change a dough. Sourdough is especially sensitive because hydration affects fermentation speed and small changes affect structure.

When bakers say “weigh your ingredients,” it’s not gatekeeping. It’s because weight is the only stable reference point.

The Core Principle

Baker’s percentages start with one simple decision: Flour is always 100%. Everything else is calculated in relation to the total flour weight.

The Golden Formula (That Explains Everything)

Here’s the entire foundation of baker’s math:

That’s it. No advanced math. No spreadsheets required.

Example: A Basic Sourdough Formula

• Flour: 500g → 100%
• Water: 350g → 70% (Hydration)
• Salt: 10g → 2%
• Starter: 100g → 20%

We didn’t decide these numbers randomly—we just expressed them relative to flour. This allows you to scale recipes up or down instantly without breaking the ratio.

Hydration: The Master Variable

If baker’s percentages had a main character, it would be hydration.

Hydration controls dough feel, fermentation speed, and crumb structure.

Understanding Hydration Ranges

• Low (60–65%): Stiff dough, easy shaping, tight crumb. Ideal for sandwich loaves.
• Medium (68–72%): Balanced extensibility, controlled open crumb. Best for beginners.
• High (75%+): Very extensible, large irregular holes (Open Crumb). Requires skill to handle.

(Want the open crumb look? Read our guide on The Science of Open Crumb)

Total Flour Weight (The Part Everyone Misses)

Here’s a detail that trips up almost every beginner: Starter contains flour and water.

So when calculating true baker’s percentages, the flour inside your starter counts toward total flour weight.

• If your starter is 100% hydration (half flour/half water).
• A 100g starter contributes 50g flour and 50g water.

Ignoring this leads to confusion. A recipe might say "70% hydration," but if you add a huge amount of liquid starter, the true hydration could be 75%+.

This is why beginner doughs often feel stickier than expected. The math wasn’t wrong—the assumptions were incomplete.

Calculating Salt and Starter Percentages

Once hydration is set, the rest becomes easier.

Salt: Usually Around 2%

Salt strengthens gluten and controls fermentation speed.

• Standard: 1.8% – 2.2%
• Lower: Dough ferments too fast; structure weakens.
• Higher: Fermentation slows noticeably; taste becomes too salty.

Starter: Typically 15–25%

Starter percentage affects the fermentation timeline and flavor profile.

• 20% (Standard): Good balance of reliability and flavor (e.g., 100g starter for 500g flour).
• Low (10%): Longer fermentation, more complex sourness.
• High (30%+): Fast fermentation, milder acidity.

Common Beginner Mistakes

“My dough is always sticky”

• Likely Causes: Hydration too high for your flour type, underdeveloped gluten, or relying on volume measurements.
• (Fix it: Hydration vs. Flour Type Guide)

“My loaf is flat”

• Likely Causes: Overhydration (too much water), weak fermentation structure, or overproofing.
• (Fix it: Troubleshooting Flat Sourdough)

Frequently Asked Questions

The Takeaway

Baker’s percentages aren’t advanced. They’re clarifying.

They take what’s already happening in your dough and give it a clear language. Once you understand Flour as the constant (100%) and Hydration as the driver, sourdough stops feeling unpredictable.

And when baking becomes predictable, it becomes enjoyable again.