The sourdough calculator bakers rely on.

A sourdough calculator converts your target dough weight and hydration into exact gram measurements for flour, water, starter, and salt. It uses baker's percentages, the industry-standard formula where every ingredient is expressed as a fraction of the total flour weight. It's the same system used by professional bakeries to scale recipes consistently, whether they're making 10 loaves or 10,000.

If you've ever read a sourdough recipe that says "75% hydration, 20% starter, 2% salt," those are baker's percentages. The calculator does the algebra for you, you just choose your batch size and the percentages you want.

Home bakers use it to scale down bakery recipes without the rounding errors that come from halving volumes. Bakery professionals use it to standardize formulas across different production batches. If you're new to sourdough, it removes the math entirely and lets you focus on the baking. Learn more about how we approach bread science on our About page.

The sourdough calculator also accounts for your starter's hydration, a detail most back-of-envelope calculations miss. Because your starter itself contains flour and water, the actual hydration of your dough depends on starter type. This tool handles all of that automatically.

Click each step to expand the full explanation, with real examples and common mistakes to avoid.

The formulas behind the calculator, with a worked example and sourced references.

Baker's percentages are just the start. Here's the broader context that turns a correct calculation into a great loaf.

Understanding Baker's Percentages

In conventional cooking, percentages are relative to the total recipe weight. In baking, they're always relative to flour. That's why a sourdough recipe can have a hydration "above 100%", it just means there's more water than flour by weight. The flour is always 100% by definition.

This system makes recipe scaling trivial. Want twice the dough? Double every number. Switching from all-purpose flour to bread flour? Keep your percentages the same, you might just need slightly less water since bread flour absorbs more. The percentages stay constant; the gram weights change.

Choosing the Right Hydration for Your Recipe

Hydration isn't just about dough texture, it affects fermentation speed, crust blistering, and crumb structure. Higher-hydration doughs (78%+) ferment faster because the water makes starches more accessible to the yeast. They also produce the signature open, irregular crumb that bakery-style loaves are known for.

Your flour type matters. Whole wheat flour absorbs significantly more water than white bread flour - a recipe at 78% hydration with whole wheat might feel similar to an 85% white flour dough. If you're substituting flours, expect to adjust hydration by 3–5% per 10% whole grain substitution.

Try our sourdough hydration calculator to compare how the same dough weight changes at different hydration levels.

How Starter Health Affects Your Dough

A calculator gives you the right ratios, but your starter's activity drives the fermentation. Peak starter activity happens roughly 4–8 hours after feeding at room temperature (68–72°F / 20–22°C). Using starter past its peak means less leavening power and a longer bulk fermentation window.

Starter percentage (inoculation rate) and temperature together control your fermentation timeline. At 20% inoculation and 72°F, most doughs reach proper bulk fermentation in 4–6 hours. Drop to 15% or cool your kitchen to 65°F and you can push that to 8–12 hours, which many bakers prefer for flavor development.

Scaling Recipes Up and Down

One of the biggest advantages of baker's percentages is painless scaling. If a recipe calls for 500g flour, 375g water, 100g starter, and 10g salt (75% hydration, 20% starter, 2% salt), and you want to make it with 1,000g flour instead, just double everything. The ratios are preserved automatically.

Use this sourdough bread calculator to work backwards from your target dough weight rather than your flour amount. It's more practical: you know you want one 750g loaf, not that you want to start with exactly 422.5g of flour.

This tool was built for anyone who bakes sourdough with a kitchen scale, which should be everyone, honestly.

• Beginners learning baker's math for the first time, the calculator removes the intimidation of percentages and lets you focus on developing feel for the dough.
• Home bakers scaling recipes from books like Tartine Bread, The Perfect Loaf, or online formulas, especially when the original serves a different batch size than you need.
• Sourdough enthusiasts experimenting with different hydration levels, starter percentages, or whole-grain substitutions, use the calculator to explore how changing one variable shifts your gram amounts.
• Small bakeries and cottage bakers who need to standardize formulas across different production runs, baker's percentages are the universal record format.
• Baking students studying the fundamentals of bread formulation taught at institutions like the San Francisco Baking Institute.

If you bake sourdough more than occasionally, understanding baker's percentages will change how you read and adapt recipes. Calculate your next loaf now - or visit our baking blog for guides on hydration, starter ratios, flour selection, and more.