Poolish & Preferment Calculator

What is a preferment?

A preferment is a mixture of flour, water, and a small amount of yeast (or sourdough starter) that ferments for several hours before being incorporated into the final dough. During that fermentation, the yeast produces carbon dioxide, alcohol, and organic acids (compounds that give bread flavour complexity, a more open crumb, and a crust that stays crispy longer).

The underlying logic is simple: yeast produces more flavourful byproducts over a long, slow ferment than it does in a fast, warm one. By pre-fermenting a portion of the dough at cool temperatures overnight, you get the time-driven flavour development without having to commit eight hours to watching the full dough.

Preferments are a standard technique in professional baking. Virtually every quality baguette, ciabatta, or focaccia produced by a serious bakery uses one. They are less common in home baking simply because they require planning ahead. The extra step is a ten-minute mix the night before, not an active commitment.

Using this calculator

Select your preferment type at the top: poolish, biga, or pâte fermentée. Then enter your total recipe flour and your target dough hydration: these are the anchors the calculator uses for all other calculations. Adjust the preferment percentage slider to control how much of your total flour goes into the preferment (25% is a solid starting point).

Set your planned fermentation time and temperature. The calculator uses these to compute a yeast amount: less yeast for a long, slow ferment; more for a short, warm one. If you're planning to ferment in the fridge overnight, toggle cold retard on and the yeast amount adjusts accordingly.

The results panel shows two stages: everything you need to mix tonight, and everything you add tomorrow to complete the final dough. The totals section at the bottom confirms your overall hydration and ingredient percentages so you can cross-check against your recipe.

Poolish vs Biga vs Pâte fermentée

Poolish is a French technique, originally developed for making baguettes. It's mixed at 100% hydration (equal weights of flour and water), which makes it loose and pourable, almost like a thick pancake batter. After fermenting, it's bubbly, light, and slightly domed. Poolish contributes a wheaty, mildly complex flavour and promotes an open, irregular crumb. It's excellent for baguettes, pizza dough, focaccia, and any bread where you want an airy interior.

Biga is the Italian equivalent. It's mixed at 50–60% hydration, stiff enough to hold its shape, more like a shaggy dough than a batter. The lower hydration slows fermentation and pushes flavour development in a different direction: earthier, more complex, with a chewier crumb and better keeping quality. Biga is standard in ciabatta, focaccia, and Pugliese, and works well in any bread where you want a more robust character.

Pâte fermentée ('old dough') is the simplest preferment of all: you save a piece of yesterday's bread dough before baking it and use it in today's batch. It ferments at full dough hydration (around 63%) and includes salt, which distinguishes it from poolish and biga. Salt slows fermentation, making pâte fermentée more forgiving. It contributes complex flavour without any special mixing step. It's just the dough you would have baked anyway.

How much preferment to use

The preferment percentage (the proportion of total recipe flour that goes into the pre-ferment) controls how much flavour development you get. Higher percentages produce more complex, pronounced flavour and a more open crumb. Lower percentages produce a subtler improvement with more predictable timing.

15–20%: Subtle. Improved flavour over a straight dough, but mild. Good for enriched breads where you don't want preferment flavours competing with butter or eggs.

25–30%: The standard range for most applications. Noticeable improvement in flavour complexity and crust quality without overwhelming the bread's other characteristics. This is where to start.

35–50%: Intense flavour development. Pronounced complexity, sometimes slightly tangy. The dough timing becomes more demanding because more of your flour has already been fermented. For experienced bakers who want to maximise flavour or who are working with long fermentations.

How to know when your preferment is ready

For a poolish, peak ripeness looks like this: the volume has roughly doubled, the surface is domed and just starting to flatten at the centre, and you can see bubbles throughout when you look through the side of the container. Pull a spoonful; it should fall in sheets or ribbons. The smell is lightly alcoholic, wheaty, and fresh. If the dome has fully collapsed and the surface looks wet and flat, it's over-ripe and will produce an overly acidic loaf.

For a biga, look for 50–75% volume increase, a slightly domed top, and the biga just beginning to pull away from the sides of the bowl. The interior should be aerated with small pockets when you pull a piece apart. It smells yeasty and wheaty with a faint alcohol note.

Timing varies with temperature. A poolish fermented at 65°F (18°C) for 14 hours will reach the same ripeness as one fermented at 75°F (24°C) for 8–9 hours. The yeast calculation in this calculator accounts for temperature, but it's always worth doing a visual check before you mix the final dough regardless of what the clock says.

Frequently asked questions

What percentage of flour should go into the poolish?

20–40% of total flour is the standard range, with 25–30% being the most common. Less than 20% and you won't notice much difference in the final bread. More than 40% can produce a very sour, boozy flavour (which some breads call for, but it's aggressive for most applications). Start at 25% and adjust based on how much flavour development you want.

How do I know when my poolish is ready to use?

A ripe poolish will have roughly doubled in volume, domed on top (the dome may be just starting to flatten), and show bubbles throughout. If you pull a spoonful, it should fall in ribbons rather than plop as a mass. The smell is slightly alcoholic and wheaty, not sour. If it smells very sour or has fully collapsed flat, it's past peak and will produce an overly acidic loaf.

Can I use sourdough starter instead of commercial yeast in the poolish?

Yes: that's called a levain (or liquid levain if built at 100% hydration). The principles are the same: a portion of your flour and water ferments ahead of time. The difference is that sourdough introduces lactic and acetic acid bacteria alongside wild yeast, producing a more complex, tangier flavour profile over a longer timeframe. The calculator is designed for commercial yeast preferments; use the Sourdough Hydration Calculator for sourdough-based recipes.

What's the difference between poolish and biga?

Hydration. A poolish is 100% hydration (equal weights of flour and water), making it pourable and loose. A biga is 50–60% hydration, stiff enough to hold its shape. The stiffness of a biga slows fermentation and produces a more complex, wheaty flavour with better keeping quality. Poolish contributes an open, airy crumb and works well for baguettes and pizza. Biga is the standard for Italian breads like ciabatta and focaccia.

Can I make the poolish in the fridge overnight?

Yes, and it's often the most practical approach. Cold-retarding the poolish (8–16 hours at around 38–42°F / 3–6°C) slows fermentation and allows for a longer, more controlled build-up of flavour. Use a bit more yeast for the fridge than for room temperature. Toggle the cold retard switch in the calculator and it will adjust the yeast amount accordingly.

Why does my final dough water show as negative?

This happens when the water in the preferment already exceeds your target total water for the recipe, usually because the preferment percentage is very high combined with a relatively low target hydration. Either increase the target hydration, reduce the preferment percentage, or switch from poolish (100% hydration) to biga (lower hydration). The calculator shows a warning when this occurs.