How it works
How it is calculated
Each 1% vol of potential alcohol needs roughly 17 g of sugar per litre. The EU uses 16.83 g/L for its official calculation; 17 g/L is the usual working figure, so it is the default here, and you can change it. Sugar per litre times the volume gives the pure sugar.
For concentrated must or rectified concentrated grape must (RCGM), the calculator divides the pure sugar by the sugar content of the product and also shows the volume to add.
Dissolved sugar adds volume (roughly 0.6 L per kg), which slightly dilutes acidity. The calculator works on the starting volume.
Check the rules before you add
In the US, sugar additions to juice are governed by TTB rules (27 CFR part 24), and some states are stricter: California does not allow sugar to be added. In the EU, enrichment is only allowed in certain wine-growing zones and years, with limits on the increase. Confirm what applies to you before dosing.
Worked example (US units)
500 gal (1,892.7 L) of must to raise by 1.0% vol: 17 g/L × 1,892.7 L = 32.2 kg of sugar, about 71 lb.
Questions winemakers ask
How much sugar raises alcohol by 1%?
About 17 g per litre, or roughly 2.3 oz per US gallon. Real yields vary with the yeast and how the fermentation goes.
How does Brix relate to potential alcohol?
A common rule of thumb is potential alcohol ≈ °Brix × 0.59, though published factors range from about 0.55 to 0.65. The must weight converter does Brix, Baumé and Oechsle.
Sugar or concentrated must?
Concentrated must raises alcohol without adding cane or beet sugar, but it also adds volume and some acidity and flavour. RCGM is neutral grape sugar. The calculator handles all three.