American flour bags list protein. Italian mills publish two more numbers from a test called the alveograph: W, for strength, and P/L, for how that strength splits between resistance and stretch. They are genuinely useful for comparing pizza flours, as long as you read them as ranges rather than precise properties of the bag in your hand.
What the alveograph measures
The test turns flour, water and salt into a dough, presses it into a thin sheet, and inflates the sheet with air until the bubble bursts. A pressure trace records what happens:
- P (tenacity) is the height of the curve: how hard the dough resists being stretched, in millimetres of water pressure. High P means a dough that pushes back.
- L (extensibility) is the length of the curve: how far the bubble stretches before it bursts, in millimetres.
- W (strength) is the area under the curve, the energy needed to inflate the bubble to bursting, reported in units of 10⁻⁴ joules. Modernist Pizza notes that this area is taken as the measure of a flour’s baking strength.
- P/L divides one by the other. A high ratio means resistance dominates; a low one means stretch does.
Two flours can share a W and handle very differently if their P/L differs.
W: strength
A higher W means a dough that can hold its structure through more: a longer fermentation, more water, or a heavier, bread-like crust. Modernist Pizza puts it in terms of style: strength suits bread-like pizzas such as al taglio and focaccia, while Neapolitan dough is made with a much lower W.
The clearest way to see what W means in practice is one mill’s range. Here is Caputo’s, with each flour’s intended use as Caputo describes it:
| Caputo flour | Protein | W | Caputo designs it for |
|---|---|---|---|
| Classica | 12% | 220–240 | Short rises |
| Pizzeria (blue) | 12.5% | 260–280 | Classic Neapolitan pizza |
| Chef’s Flour / Saccorosso (red) | 13% | 300–320 | Long rises in the fridge |
| Nuvola Super | 13.5% | 320–340 | Preferments and high-hydration doughs |
| Americana | 14.25% | 360–380 | New York and neo-Neapolitan pizza |
| Americana Super | 15.25% | 380–400 | New York, Detroit and Sicilian; ferments over 72 hours |
Specifications as published by Mulino Caputo and its US importer, Orlando Foods, checked October 14, 2026. Orlando lists the Pizzeria bag at W 260–270. Within this one mill, W climbs with protein and with the length of fermentation each flour is meant for. That pattern belongs to one mill’s range; don’t carry it across mills, because W also depends on how the test is run, as the sections below explain.
P/L: resistance against stretch
The EU specification for Pizza Napoletana asks for a P/L between 0.50 and 0.70. Caputo’s pizza flours sit at 0.45 to 0.60.
In the hand, a high P/L dough springs back when you stretch it, and a low P/L dough stretches easily but can be slack and hard to keep in shape. Time changes this: Modernist Pizza notes that a Neapolitan dough made two days ahead is easy to shape however strong its gluten, because it has had time to relax. So if a dough keeps shrinking back, give it longer before you blame the flour. The shrinking dough guide covers the other causes.
The full Neapolitan flour specification
The EU’s Pizza Napoletana specification (Regulation 97/2010) sets out the flour’s characteristics:
| Measure | Required range | What it describes |
|---|---|---|
| W | 220–380 | Strength (alveograph) |
| P/L | 0.50–0.70 | Resistance against stretch (alveograph) |
| Absorption | 55–62 | Water the flour takes up (farinograph) |
| Stability | 4–12 | How long the dough holds its consistency while mixing (farinograph) |
| E10 | 60 maximum | How much the dough softens after 10 minutes of mixing (farinograph) |
| Falling number | 300–400 | Enzyme (amylase) activity; a higher number means less |
| Dry gluten | 9.5–11 g per 100 g | Gluten content |
| Protein | 11–12.5 g per 100 g | Protein content |
The W window is wide: anything from a fairly soft flour to quite a strong one qualifies. The protein window is narrow, and typical American bread flour sits at or just above its top. The falling number has a practical link to browning: flour with less amylase leaves less sugar for the crust, which is one reason home bakers sometimes add diastatic malt. For the rest of the Naples rules, see the AVPN standard.
Why you can’t convert protein into W
Many pizza guides print tables that turn protein percentages into W ranges. The evidence doesn’t support that precision.
- The test shifts with hard wheat. The standard alveograph method mixes every flour at the same fixed hydration. The Canadian Grain Commission showed that this under-hydrates hard-wheat flour: one bread-wheat flour scored W 510 at the standard hydration and W 125 when tested with the water it actually absorbs. American bread flour is hard-wheat flour, so a W for it isn’t directly comparable to a W for a soft-wheat 00.
- Protein is a rough guide on its own. Modernist Pizza warns that protein varies widely from brand to brand within each flour category, and argues that no single number on a spec sheet matters most; it suggests weighing several.
Protein still tells you something: within a category, more protein usually means more gluten and more water absorbed. It just can’t be turned into a W number.
Choosing flour without a W number
- Match the flour to the style and the schedule. For a dough that spends two or three days in the fridge, choose a flour its maker describes for long rises, such as Caputo’s red bag, or a bread flour. For a same-day dough, a softer flour is fine.
- Read the dough. If it slackens or tears before the end of its schedule, try a stronger flour or a shorter ferment. If it keeps springing back, give it more time or a little more water.
- Stay with a flour that works. Modernist Pizza suggests testing similar flours side by side before settling on one, and Forkish notes that even one mill’s flour changes a little with each year’s harvest.
- Blend if you need something in between. Forkish uses bread flour or Caputo’s red bag for the long-fermenting biga in one dough and Caputo’s blue bag or all-purpose flour for the final mix.
For which flour suits which pizza and oven, see the best flour for pizza dough; for Caputo’s bags in detail, see Caputo Pizzeria vs. Chef’s Flour vs. Nuvola.
Sources
- European Commission, Regulation (EU) No 97/2010, Pizza Napoletana TSG, annex II: flour characteristics.
- Nathan Myhrvold and Francisco Migoya, Modernist Pizza (2021), volume 1, pages 278–279 (the alveograph, the W number and reading spec sheets) and 280 (flour types and protein).
- Nancy Edwards and Jim Dexter, Canadian Grain Commission, “Alveograph: sources of problems in curve interpretation with hard common wheat flour” (2008): fixed-hydration testing, P, L and W units.
- Ken Forkish, The Elements of Pizza (2016), chapter 4 (flour and harvest variation) and chapter 6 (the biga dough).
- Mulino Caputo, Caputo USA and Orlando Foods: published protein, W and P/L for Caputo flours, checked October 14, 2026.