A poolish is a pre-ferment originating from Polish bakers (hence the name), widely used in French baking. It's a mixture of equal parts flour and water (100% hydration) with a small amount of yeast, fermented for 4-16 hours before mixing into the final dough. It adds flavour, extensibility, and a more open crumb.

How much of the flour should go into the poolish?

Typically 30-50% of the total flour weight. Using more poolish (50%) gives a stronger flavour contribution and more open crumb. Using less (30%) gives a more subtle effect. For baguettes, 33-50% is common.

How do I know when the poolish is ready?

A ripe poolish will have doubled or tripled in size, have a domed or slightly concave surface covered in bubbles, and smell pleasantly yeasty and slightly tangy. If it has collapsed significantly and smells very sour, it's over-fermented.

Why does yeast amount change with fermentation time?

Longer fermentation times need less yeast because the small amount has more time to multiply and ferment. Too much yeast for a long ferment means the poolish over-ferments, becoming too acidic and losing its lift.

How long should a poolish ferment?

A poolish should ferment at room temperature for 8-16 hours until it is bubbly, domed, and just starting to collapse. Shorter fermentation (8 hours) works if your kitchen is warm (24 degrees C+). Longer fermentation (12-16 hours) in a cooler kitchen (18-20 degrees C) develops more complex flavour.

Poolish Calculator — Free Online Tool

How We Calculate This

A poolish is a 100% hydration pre-ferment — equal weights of flour and water with a tiny amount of yeast. The yeast quantity depends on how long you plan to ferment it.

The Calculation

Poolish flour = Total flour × poolish percentage (30-50%)
Poolish water = Poolish flour (100% hydration, equal weights)
Poolish yeast = Varies by fermentation time
Remaining flour = Total flour − Poolish flour
Remaining water = Total water − Poolish water

Yeast Guide (instant, per kg poolish flour)

As a baker's percentage of the poolish flour, the established schedule (Weekend Bakery; King Arthur Baking) is roughly: up to 8 hours 0.23–0.33%, up to 12 hours 0.1–0.2%, and up to 16 hours 0.03–0.08%. Use the higher end in a cool kitchen (winter, ~18 °C) and the lower end when it is warm (~24 °C). Converted to grams per kg of poolish flour:

4 hours: ~6g per kg flour (~0.6%)
8 hours: ~2.5g per kg flour (~0.25%)
12 hours (overnight): ~1.5g per kg flour (~0.15%)
16 hours: ~0.5g per kg flour (~0.05%)

Frequently Asked Questions

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Last updated: February 2026

All calculations are based on standard ratios and conversions. Results may vary with specific ingredients, equipment, and conditions.