Chaptalization calculator

The Chaptalization Calculator works out how much sugar to add to a wine must to raise it from its current sugar reading to a target sugar reading — chaptalization, the practice of adding sugar to bump up a must's potential alcohol.

Two things to know before you use it:

• It's a winemaking reference estimate, with no government formula behind it, and never valid for a tax or label filing.
• Chaptalization is legally restricted or prohibited in some winegrowing regions. This calculator enforces no legal limit — it's recipe math only. The calculator carries an advisory note saying so; check the rules for your jurisdiction.

On the hub it sits in the Estimates (non-regulatory) section, and the calculator opens with a Non-regulatory estimate badge and a highlighted note. It's free, needs no account, and computes in your browser.

Open the calculator

• On the public site: in the top navigation choose Tools, then — in the Estimates (non-regulatory) section — on the Chaptalization card choose Open calculator.
• Inside the app: in the navigation choose Tools, then on the Chaptalization card choose Open calculator.

Find the sugar to add

1. In Current must reading, enter the must's current reading, and set its Reading unit to °Brix (the default) or Specific gravity.
2. In Target must reading, enter the reading you want to reach, and set its Reading unit the same way. A Brix reading must be between 0 and 40; a specific gravity between 0.98 and 1.2.
3. In Must volume, enter the volume of must, and from Unit choose it (Milliliters (mL), Liters (L) — the default — U.S. gallons, Wine gallons, Barrels (31 U.S. gal), or Fluid ounces).
4. From Show sugar in, choose the unit for the result: Grams (g) (the default), Ounces (oz), Kilograms (kg), or Pounds (lb).
5. Sugar to add, in the unit you chose, appears once the two readings and a volume are all valid.

If your target is at or below the current reading, the calculator tells you no sugar is needed — chaptalization only raises the sugar level — rather than showing a negative amount. Above roughly 25 °Brix at the target, it warns that a stuck fermentation is likely.

Worked example

Raising 20 L of must from 18 °Brix to 22 °Brix, showing the result in grams:

1. Current must reading: 18, Reading unit: °Brix
2. Target must reading: 22, Reading unit: °Brix
3. Must volume: 20, Unit: Liters (L)
4. Show sugar in: Grams (g)

The calculator shows Sugar to add 800 g.

A note on this calculator's factor

The calculator says on-screen that it uses a provisional working factor of 10 g/L of sugar per °Brix, pending expert verification. Published winemaking guidance for this figure varies (roughly 10–17 g/L depending on the must), so treat the result as a starting point: add the sugar, then confirm with a hydrometer reading and top up if needed. This factor may change once it's reviewed, which would shift the sugar figure the calculator gives.

When to reach for it

Reach for the Chaptalization Calculator when you're planning to sweeten a must up to a target before fermentation and want a starting sugar amount. Because of the provisional factor and the legal restrictions above, treat its output as guidance, not a final dose — the page-bottom disclaimer confirms it's a reference tool, never a system of record for a filing.