Built by bakers, for bakers.

Sourdough Calculator started as a personal spreadsheet. We were baking sourdough regularly and getting frustrated every time we wanted to change batch sizes. Scale a recipe down from 1,000g to 750g? Time for arithmetic. Swap to a stiffer 75% hydration starter? Now you need to recalculate water and flour again.

Baker's percentages solve all of that, but they're intimidating if you didn't learn them formally. We built this calculator so anyone can use professional baking math without needing to understand the algebra behind it.

How We Approach Accuracy

The formula behind this calculator is the same one taught at the San Francisco Baking Institute (SFBI) and documented in Chad Robertson's Tartine Bread. It's standard baker's percentage math, no shortcuts, no approximations.

The one thing most simple calculators miss: starter hydration. Your starter isn't just a leavening agent, it contains flour and water in its own right. A 100% hydration starter is 50% flour, 50% water by weight. A 75% starter is about 57% flour, 43% water. When you add 100g of starter to your dough, you're adding different amounts of flour and water depending on its hydration level. Our calculator accounts for all of that, so your actual dough hydration matches your target.

We verify our calculations against King Arthur Baking Company's reference formulas and cross-check edge cases (very low hydrations, high starter percentages) by hand. If you spot an error, please email us, we take accuracy seriously.

Our Editorial Process

Every article on our sourdough blog goes through the same process: we test the claims in our own baking before publishing, cite primary sources (SFBI, King Arthur, peer-reviewed food science where relevant), and include specific numbers rather than vague guidance. We don't publish "some bakers prefer..." without a specific example.

We update posts when baking science moves forward or when readers send corrections. The "Last Updated" date on every page reflects genuine updates, not just a date refresh for SEO purposes.

Who We Are

We're passionate home bakers and baking enthusiasts who built this tool to make baker's percentages accessible to everyone, from first-time sourdough bakers to seasoned artisans. We're not a bakery, a cooking school, or a media company. We're people who bake sourdough regularly and wanted better tools. The site is free, has no sign-up, and never will.

Our collective experience spans home baking, recipe development, and software engineering. We bring the same rigor to a sourdough formula that we'd bring to a software specification: test it, document it, and publish the source of truth.