Reverse Hydration Calculator

Enter the ingredient weights you're about to mix. Get the effective baker's percentages back — with starter discount applied.

Effective flour (incl. starter flour)
500 g
Effective water (incl. starter water)
375 g
Effective hydration
75%
Salt %
2%
Starter contributed flour
50 g
Starter contributed water
50 g

When to use this

  • Verifying a recipe before mixing ("is this really 75%?")
  • Converting a volumetric recipe to baker's percentages
  • Comparing two formulas side-by-side
  • Scaling a dough after ingredients are already measured

The gear that makes the math work

A short, honest baking kit. The scale matters most — every weight on this page is in grams. The Dutch oven is what turns a good crumb into a great crust.

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  • Digital kitchen scale (0.1 g)Digital kitchen scale (0.1 g)

    Baker's percentage is by weight, not volume — a 0.1 g scale is what makes the math on this page accurate.

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  • Dutch oven / combo cookerDutch oven / combo cooker

    Traps steam for the first bake phase — the single biggest factor in oven spring and a blistered, glossy crust.

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  • Banneton proofing basketBanneton proofing basket

    Wicks moisture and holds shape during the final proof, so high-hydration dough doesn't spread flat.

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  • Bread lameBread lame

    A sharp lame scores clean ears — the cut that decides whether the loaf opens up or bursts at the side.

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  • Bench scraperBench scraper

    Steel scraper handles wet, sticky high-hydration dough without tearing the gluten you just built.

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  • High-protein bread flourHigh-protein bread flour

    The math assumes ~12–14% protein. Real bread flour absorbs the hydration you calculate — all-purpose won't.

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  • Danish dough whiskDanish dough whisk

    Mixes shaggy, high-hydration dough in seconds without the gluey mess of a spoon or your hands.

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Or learn the craft by ear

The numbers here are the what; a good baking book is the why. An Audible trial gets you any title free — Michael Pollan’s Cooked(the “Air” chapter is the best story ever told about why bread rises) is a perfect first listen.

Start a free Audible trial →

As an Amazon Associate, SourdoughHydration earns from qualifying purchases at no extra cost to you. More on how this is funded.

Gear guides — what actually matters

Common questions

What does the reverse calculator do?

It takes raw ingredient weights — flour, water, starter, salt — and returns the effective baker's percentage values. Useful when you're ad-libbing a recipe and want to know the resulting hydration before mixing.

Why is effective hydration different from water-to-flour ratio?

Because the starter contains both flour and water. If you have 450g added flour and 325g added water, but your 100g starter at 100% hydration brings in 50g more flour and 50g more water, the effective totals are 500g flour and 375g water — 75% hydration, not 72%.

Does starter hydration matter here?

Yes. A stiff starter (50% hydration) at 100g contributes 67g flour + 33g water. A liquid starter (100%) at the same weight contributes 50g + 50g. The math is automatic in this calculator.