Baker's Percentages Explained Simply (For New Sourdough Bakers)

Baker's percentages are the language of professional baking. Once you understand them, you can read any recipe, scale recipes up or down, and develop your own. Here's the simplest explanation.

The core idea

In baker's percentages:

• Total flour is always 100%
• Every other ingredient is expressed as a percentage of flour weight
• Percentages don't add up to 100% (water might be 75%, salt 2%, etc.)

That's the whole concept.

A worked example

A typical sourdough recipe:

• 500g flour (100%)
• 350g water (70%)
• 100g starter (20%)
• 10g salt (2%)

How to calculate each percentage:

• Water: 350 ÷ 500 × 100 = 70%
• Starter: 100 ÷ 500 × 100 = 20%
• Salt: 10 ÷ 500 × 100 = 2%

Now you can recreate this recipe at any size:

• For 1000g flour: 700g water, 200g starter, 20g salt
• For 250g flour: 175g water, 50g starter, 5g salt

The recipe scales perfectly while maintaining its character.

Why this works

Baker's percentages let you:

• Scale recipes mathematically
• Compare recipes (one with 75% hydration vs. one with 85%)
• Adjust ratios systematically (more water, less starter)
• Develop your own recipes
• Communicate with other bakers

A recipe in cups doesn't tell you what's actually happening. A recipe in baker's percentages does.

Common percentages in sourdough

These ranges cover most sourdough:

• Hydration (water): 65–85%
• Lower (65%): tight crumb, easy handling
• Higher (85%): open crumb, harder to handle

• Starter: 15–30%
• Lower (15%): slow fermentation
• Higher (30%): fast fermentation

• Salt: 1.8–2.2%
• Almost always close to 2%

• Sugar (in enriched dough): 5–12%
• Butter (in enriched dough): 5–40%
• Eggs (in enriched dough): 5–25%
• Milk (replacing water): 0–30%

Calculating your starter's contribution

A 100% hydration starter is half flour, half water by weight.

For 100g of starter at 100% hydration:

• 50g of "starter flour"
• 50g of "starter water"

When calculating total flour and water in your recipe, include both the dough flour/water AND the starter's contribution.

For a 500g flour recipe with 100g starter (100% hydration):

• Flour total: 500g + 50g (from starter) = 550g
• Water total: 350g + 50g (from starter) = 400g
• Actual hydration: 400 ÷ 550 = 73% (slightly higher than the recipe stated)

This is why some bakers round their numbers — perfect math is harder than rough estimates.

A quick recipe check

When you see a sourdough recipe, calculate:

• Hydration: water ÷ flour
• Starter percentage: starter weight ÷ flour weight
• Salt percentage: salt weight ÷ flour weight

These three numbers tell you what kind of bread the recipe will produce.

Scaling recipes

To scale a recipe:

1. Calculate baker's percentages from the original
2. Decide on new flour weight
3. Apply percentages to new flour weight

Example: scale a 500g flour recipe to 250g flour.

Original:

• 500g flour, 350g water, 100g starter, 10g salt

Scaled:

• 250g flour
• 250 × 0.70 = 175g water
• 250 × 0.20 = 50g starter
• 250 × 0.02 = 5g salt

The scaled recipe has the same ratios.

Adjusting hydration

If you want a wetter dough, increase the percentage:

• Original: 70% hydration → 350g water for 500g flour
• More hydrated: 80% hydration → 400g water for 500g flour

Want a drier dough? Decrease the percentage. This is much more reliable than guessing "a little more water" by eye.

Adjusting starter

To slow fermentation: decrease starter percentage.

• Original: 20% starter → 100g starter for 500g flour
• Slower: 15% starter → 75g starter for 500g flour

To speed up: increase. The recipe scales accordingly.

A note on flour blends

When you use multiple flours, the total of all flours equals 100%:

• 80% bread flour + 20% whole wheat = 100% total flour
• For 500g total flour: 400g bread + 100g whole wheat

Calculate hydration on the total flour weight, not the individual flours.

Comparing recipes

When you see two recipes:

Recipe A: 500g flour, 380g water, 100g starter, 10g salt

• Hydration: 76%
• Starter: 20%
• Salt: 2%

Recipe B: 700g flour, 420g water, 140g starter, 14g salt

• Hydration: 60%
• Starter: 20%
• Salt: 2%

Despite the different absolute amounts, you can immediately see Recipe A is much wetter. Recipe A will be more open-crumbed; Recipe B will be tighter.

When you don't need exact percentages

For everyday baking, you don't need to calculate every recipe to the decimal:

• 70% hydration vs. 72% hydration is barely noticeable
• 20% starter vs. 22% starter is barely noticeable
• 1.8% salt vs. 2% salt is barely noticeable

The point of percentages isn't precision; it's consistency and reproducibility.

When percentages really matter

In some cases, percentages are critical:

• Salt: 1.5% is too low, 3% is too high
• Hydration over 80%: significantly different handling
• Starter under 10%: very slow fermentation
• Salt approach to 0% (forgotten): bread is bland and weak

Stay within standard ranges and percentages give you confidence.

A practical tip

I keep a small notebook with my favorite recipes written in baker's percentages. For example, my everyday country loaf is 100% bread flour, 75% hydration, 20% starter, and 2% salt. For a 500g batch that's 500g flour, 375g water, 100g starter, and 10g salt. For a 1000g batch, 1000g flour, 750g water, 200g starter, and 20g salt.

This way I can scale any recipe in my head.

The mental model

Once you understand baker's percentages, you start thinking differently about bread:

• "This recipe is 78% hydration; I need to handle it carefully"
• "This recipe is 30% starter; bulk will be fast"
• "This recipe has 25% whole wheat; I should add a bit more water"

Percentages give you intuition that no recipe-following can match.

A common mistake

Some bakers assume "100%" means the total of all ingredients should sum to 100%. This is wrong.

The total of percentages in a sourdough recipe is usually 200%+:

• Flour: 100%
• Water: 75%
• Starter: 20%
• Salt: 2%
• Total: 197%

This is normal. The "100%" only refers to the flour weight as the base.

When to start using percentages

For new bakers:

• First 5 bakes: just follow the recipe
• Bakes 5–15: observe how the dough behaves
• Bakes 15+: start calculating percentages, comparing recipes
• Bakes 30+: develop your own recipes using percentages

Don't worry about percentages immediately. They're a tool for when you're ready to deepen your understanding.

Resources for learning more

• "Bread: A Baker's Book of Techniques and Recipes" by Jeffrey Hamelman — the classic reference
• Online baker's percentage calculators
• King Arthur Flour's website has many recipes in percentages

A final note

Baker's percentages aren't intimidating. They're just a way of thinking about ingredients in proportion to flour.

Once you start using them:

• Recipes become more transparent
• Scaling becomes effortless
• Your own recipes become possible
• Communication with other bakers becomes precise

This is the difference between a recipe-follower and a baker who understands what they're doing.

If you're serious about sourdough, learn baker's percentages. It's the most important conceptual upgrade you can make.

The math is simple. The implications are vast.