Calculate how much sugar to add to fruit must for the wine to reach your planned strength and how many grams of potassium metabisulphite you need for a given SO₂ dose.
How much sugar is needed for 1% alcohol?
It is assumed that about 17 g of sugar per litre of must gives 1% vol of alcohol. Fruit already contains some sugar, so first measure the must with a hydrometer – the calculator subtracts the natural sugar and accounts for the volume increase after dissolving sugar.
What is metabisulphite for?
Potassium metabisulphite releases SO₂, which protects wine against oxidation and wild yeast. It is used before fermentation and when racking the wine off the sediment, usually at 30–60 mg/l.
How we calculate
We assume about 17 g of sugar per litre gives 1% vol of alcohol. Sugar already in the must ≈ 10 × °Blg g/l (approximately). Dissolved sugar increases the volume by about 0.63 l/kg – we take that into account. Potassium metabisulphite contains about 57% SO₂.
Frequently asked questions
How much sugar for 1% alcohol in wine?
About 17 g of sugar per litre of must gives about 1% vol of alcohol.
How long does wine ferment?
Vigorous fermentation usually lasts 1–2 weeks, secondary fermentation from a few weeks to several months. The wine is ready for racking when it clears and the hydrometer reading is stable.
Can metabisulphite be overdosed?
Yes – too high a dose gives a noticeable sulphur smell and can inhibit the yeast. Stick to 30–60 mg/l SO₂ and weigh the metabisulphite accurately.
When should I add sugar to wine?
Ideally in 2–3 portions: some at the start, the rest after a few days of vigorous fermentation, always dissolved in a little must.