Sourdough pizza dough calculator
Sourdough pizza dough has one number every recipe argues about: how much starter. The honest answer is a schedule question, not a constant — so pick when you bake, set your batch, and read off a recipe where the starter’s own flour and water are already accounted for.
When do you bake?
2 h room, 24 h fridge (4 °C) — the model doses your starter at 21% of the flour.
Assumes an active, 100%-hydration starter — its flour and water are already subtracted from the adds, so the hydration stays honest. Oil, sugar, pan styles and the clock-time schedule live in the full calculator.
How the dose is decided
The model turns your plan into effective hours — fermentation roughly doubling in speed every 7 °C — and doses the starter inversely, clamped to 2–40% of the recipe’s flour. The anchor worth memorizing: a 24-hour rise at 20 °C wants 6.25% starter.
The four plans above, worked for the default 4 × 260 g batch:
| The plan | Starter | For the batch |
|---|---|---|
| 4 h warm (24 °C) | 25.2% | 159 g |
| 8 h at room (21 °C) | 17.0% | 107 g |
| 2 h room, 24 h fridge (4 °C) | 21.0% | 133 g |
| 2 h room, 48 h fridge (4 °C) | 12.4% | 79 g |
These come straight out of the calculator’s fermentation model, so the tool and the full recipe can never disagree.
Why the fridge plan wants more, not less
The counterintuitive row in that table is honest: 2 h room, 24 h fridge (4 °C) wants more starter than 8 h at room (21 °C), despite lasting three times as long on the wall clock. Cold is the reason — at 4 °C the microbes barely work, so a fridge hour counts for a fraction of a room hour. Spelled out in effective hours: the same-day plan is worth 8.8 h of room-temperature work, the overnight-fridge plan only 7.1 h.
That’s not a reason to skip the fridge — the cold buys flavor, flexibility and a stronger dough skin. It’s a reason to dose by effective hours instead of guessing. The cold fermentation guide covers that half of the plan.
The starter is part of the recipe
A 100%-hydration starter is half flour, half water, and at pizza doses it’s far too big to ignore. The tool counts it toward the totals and subtracts it from the adds — the rebalancing most sourdough recipes skip.
Worked through the default batch on the next day plan: the recipe’s true flour is 631 g, so the starter is 21.0% of that — 133 g, about 8 ⅞ tbsp. Its 66 g of flour and 66 g of water come off what you weigh into the bowl, which is how the total lands on 1040 g at exactly 62% hydration.
Questions from the counter
How much starter per kilo of flour?
On the 24-hour anchor plan, 63 g per 1000 g of flour — but the honest answer moves with your schedule, which is the whole point of the tool. Shorter and warmer wants more; longer and cooler wants less.
Can I use starter straight from the fridge, or discard?
The math assumes an active starter — recently fed, at or near its peak. A cold, hungry one ferments slower than the model expects, so everything runs late. Discard is for crackers; pizza deserves the fed jar.
My starter isn’t 100% hydration — does it matter?
A little, not much. A stiffer starter brings more flour and less water per gram, so the dough lands slightly drier than planned — at typical doses that’s a fraction of a hydration point. Add a splash of water or ignore it.
Why is the dose so much bigger than a yeast dose?
Because a starter is mostly flour and water with wild yeasts as a minority share — same-rise it’s about 75× an instant-dry dose by weight. The yeast converter swaps between all four kinds.
The rest of the recipe
This tool weighs the sourdough essentials. The full calculator adds the rest: ten pizza styles with oil and sugar where they belong, pan sizing, a clock-time schedule for your ferment, and the same starter math underneath.
The clock is a suggestion. The dough is the boss. In bocca al lupo!
Impasto is a free pizza dough calculator for Neapolitan, New York, Roman, Sicilian, Detroit, thin crust and focaccia doughs — flour, water, salt and yeast weighed in baker's percentages, with the fermentation schedule written for you.