TL;DR

A sourdough hydration calculator converts your recipe into baker's percentages so you can scale, adjust, or compare loaves without guessing. Hydration is the weight of water divided by the weight of flour, expressed as a percentage — most home sourdough sits between 70% and 85%. Skip the math: get the free CrumbCoach app for iPhone or Android — the built-in hydration calculator handles starter correction automatically (most web calculators get this wrong).

I was elbow-deep in a 1.2kg dough at 6am last Tuesday when I realized I'd doubled my recipe wrong. Again. I'd scaled the flour, scaled the water, forgot the starter contributes both — and ended up with a loaf so wet it spread across the parchment like a pancake. That was the morning I finally stopped winging hydration math and built a calculator I actually trust.

If you've ever stared at a recipe that says "500g flour, 375g water" and wondered whether your starter counts as flour, water, or both, this is the post for you. Baker's percentages are the language professional bakeries use to talk about dough, and once you understand them, you can adjust any recipe to your kitchen, your flour, and your starter without losing the bread.

What is a sourdough hydration calculator?

A sourdough hydration calculator is a tool that takes the ingredient weights in your recipe — flour, water, starter, salt — and tells you the dough's hydration percentage by dividing total water weight by total flour weight. It accounts for the flour and water already inside your starter, which a basic water-divided-by-flour calculation gets wrong by 5-10%.

How baker's percentages actually work

The rule is simple: flour is always 100%. Everything else is expressed as a percentage of the flour weight. If a recipe calls for 1000g flour and 750g water, hydration is 75%. Salt at 20g is 2%. Starter at 200g is 20%.

The point of doing it this way is scaling. Once you know your favorite loaf is 80% hydration, 2% salt, and 20% starter, you can make a single boule, a triple batch for a market drop, or a half loaf for a Tuesday night dinner — and the bread comes out the same. You're not memorizing recipes anymore. You're memorizing ratios.

Here's a clean example using a basic country loaf at 75% hydration:

Ingredient	Weight	Baker's %
Bread flour	1000g	100%
Water	750g	75%
Active starter	200g	20%
Salt	20g	2%
Total dough weight	1970g	197%

That total of 197% is the "total formula percentage" and it'll always be more than 100% because everything you add stacks on top of the flour. Don't let it confuse you — flour is still the only thing that's 100%.

The mistake most home bakers make with hydration math

Here's what tripped me up for years: your starter is not pure water. A typical 100% hydration starter is half flour, half water by weight. So a 200g scoop of starter is really 100g flour + 100g water that you need to add to your totals before calculating hydration.

Most online calculators ignore this. They just take the water you poured into the bowl and divide by the flour you poured into the bowl, ignoring what's already living in your starter jar. That's why your 75% hydration calculation can produce a dough that behaves like 80% — the math undercounts.

The corrected formula:

true hydration = (water added + water in starter) / (flour added + flour in starter)

For our example above:

Water added: 750g
Water in starter: 100g (half of 200g)
Flour added: 1000g
Flour in starter: 100g (half of 200g)
True hydration: 850 / 1100 = 77.3%

That 2.3% difference doesn't sound like much. But it's the difference between a dough you can shape and a dough that slumps when you try.

What hydration range should you actually use?

Most baking guides will tell you "higher hydration = more open crumb, so push for 85%+." That's actually wrong for most home setups. The open-crumb-at-all-costs advice ignores that your kitchen, your flour protein content, and your oven matter as much as the water you pour. I've baked tighter, prettier loaves at 72% in a humid Houston summer than I have at 82% in a dry winter house.

Here's a more honest hydration guide based on what most home bakers actually have access to:

Hydration	Best for	What you need
65-70%	Beginners, sandwich loaves, enriched doughs	Any all-purpose or bread flour
70-75%	Standard country loaves, batards	Bread flour, basic shaping skills
75-80%	Open-crumb hearth breads	Strong bread flour (12%+ protein), confident shaping
80-85%	Ciabatta-style, very open crumb	High-protein flour, lots of folds, banneton
85%+	Pizza, focaccia, advanced bread	High-extraction or specialty flour

If you're under 6 months into your sourdough journey, stay at 72-75% until your shaping is consistent. The crumb difference between 75% and 82% is mostly invisible in a properly handled loaf, and the shaping difference is enormous.

How to calculate hydration when you change one ingredient

This is where baker's percentages earn their keep. Say you've been baking a 75% hydration loaf with 1000g flour, and you want to add 200g of whole wheat without changing the hydration. What changes?

The flour total stays at 1000g — you're just swapping 200g of white for whole wheat. But whole wheat absorbs more water than white flour, roughly 5-10% more. So to maintain the same dough feel, you'd actually push the water from 750g (75%) to around 790-800g (79-80%). The percentage on paper goes up, but the dough feels the same.

Or say you want to scale your 1000g loaf down to a 600g flour mini-loaf for a single-person household. Every ingredient gets multiplied by 0.6:

Flour: 600g
Water: 450g (75% of 600)
Starter: 120g (20% of 600)
Salt: 12g (2% of 600)

The bread tastes identical. The hydration is identical. You just made less of it. This is the moment most bakers stop relying on "recipes" and start relying on formulas.

Why this matters for your bakery business

If you're selling bread under cottage food law, hydration math isn't just a craft question — it's a cost question. Every gram of flour is money out the door. When you can calculate hydration accurately, you can:

Price loaves correctly because you know exactly how much flour each one uses
Scale a recipe from a single boule to a 20-loaf market batch without breaking it
Substitute flour types (sub specialty flours, whole grains) without ruining a sold-out menu
Train a helper or family member to bake the same loaf you do

This is exactly why CrumbCoach combines hydration math with recipe costing — every recipe in your account auto-calculates hydration as you adjust ingredients, and cost-per-loaf updates with it. Available on the iPhone and Android app.

The 4-step process I use every bake

Weigh your starter and assume 50/50 split. A 100% hydration starter (the standard) is half flour, half water by weight. Note both numbers separately.
Add your starter flour to your bowl flour, your starter water to your bowl water. This gives you your true totals.
Divide water by flour. That's your real hydration.
Adjust by 1-2% based on flour absorption. Whole wheat, rye, and high-extraction flours absorb more. Standard white bread flour holds the calculated number well.

If you do this for every bake for a month, you'll stop needing a calculator. The numbers become muscle memory. But until then, the free CrumbCoach app (iPhone / Android) does the starter-correction math for you and saves your formulas — so you can pull up your "favorite country loaf at 75%" with one tap instead of rebuilding it from scratch.

Frequently asked questions

What hydration is best for beginner sourdough?

Start at 70-72% hydration with standard bread flour. It's wet enough to develop good gluten and crumb, but dry enough to shape without sticking to everything. Once your shaping is consistent, push to 75% and only go higher if your kitchen and flour support it.

Does my starter count toward hydration?

Yes — both the flour and water inside your starter need to be added to your totals before you calculate hydration. A 100% hydration starter is roughly half flour and half water by weight, so 200g of starter adds 100g of flour and 100g of water to your dough.

Why is my dough wetter than the hydration math suggests?

Three common reasons: your starter isn't actually 100% hydration (it might be 90% or 110%), your flour absorbs less water than the recipe assumes, or your environment is humid. Drop your water by 2-3% and see if the dough feels right — adjust from there.

Can I use baker's percentages for non-sourdough recipes?

Absolutely. Baker's percentages work for any bread or pastry recipe — yeasted bread, brioche, croissants, pizza dough. The flour-is-100% rule is universal. It's especially useful for enriched doughs where butter, eggs, and sugar all express as percentages of flour weight.

What's the difference between hydration and total formula percentage?

Hydration is only water divided by flour. Total formula percentage adds up every ingredient in the recipe (flour at 100%, water, salt, starter, fats, sugars, etc.) and will always be greater than 100%. Hydration tells you about dough texture. Total formula percentage tells you about dough weight and yield.

CrumbCoach automatically calculates hydration, baker's percentages, and cost-per-loaf for every recipe in your account — so you can price, scale, and adjust without spreadsheets.

Sourdough Hydration Calculator & Baker's Percentages