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Residual sugar, usually shortened to RS, is the sugar left in a wine after fermentation stops. It is measured in grams per litre. Under 4 grams a litre the wine counts as dry. Over 45 grams a litre it counts as sweet.
That is the short version. The longer version is more useful, because the number on the lab sheet and the sweetness you actually taste are two different things, and a wine can easily fool you in either direction.
Table of Contents
Residual Sugar in One Paragraph
Yeast eats the sugar in grape juice and turns it into alcohol. If it runs out of sugar, you get a dry wine. If it stops early, or if there was more sugar than it could cope with, the leftovers stay in the bottle. Those leftovers are the residual sugar. A wine almost never drops below 1 gram a litre, because a few sugars simply cannot be eaten by yeast at all.
The Residual Sugar Chart
European labelling rules tie these words to real numbers, and because so much of what we drink in Australia is either imported or made for export, the same words turn up on our shelves. Still wines first.
| What the label says | Residual sugar | What it tastes like |
|---|---|---|
| Dry or Sec | Up to 4 g/l | No sweetness at all, just fruit |
| Medium dry or Demi-sec | 4 to 12 g/l | A faint roundness, easy to miss |
| Medium or Medium sweet | 12 to 45 g/l | Clearly sweet, still drinkable with food |
| Sweet or Doux | More than 45 g/l | Dessert territory |
There is one wrinkle. The upper limit for dry can be lifted to 9 grams a litre, and medium dry to 18, when the wine has enough acidity to balance it. That is why an Australian Riesling can carry 8 grams of sugar and still taste bone dry.
Why Sparkling Wine Labels Read Backwards
This is the part that catches everyone out, including people who have been buying wine for years. On a bottle of fizz, Extra Dry is sweeter than Brut. Not a misprint.
| What the label says | Residual sugar | In plain English |
|---|---|---|
| Brut Nature | Up to 3 g/l | Nothing added, austere and bracing |
| Extra Brut | Up to 6 g/l | Very dry |
| Brut | Up to 12 g/l | The standard, and what most people want |
| Extra Dry or Extra Sec | 12 to 17 g/l | Sweeter than Brut, despite the name |
| Dry or Sec | 17 to 32 g/l | Noticeably sweet |
| Demi-sec | 32 to 50 g/l | Dessert fizz |
| Sweet or Doux | More than 50 g/l | Rare, and very sweet |
If you want the wider fizz picture, the Prosecco and Cava comparison covers the styles. The reason for the naming is historical. Nineteenth century Champagne was sweet by our standards, with some bottles measured at around 150 grams a litre, so the terms were set against a much sweeter starting point and never updated. Reach for Brut, and if the label says Extra Dry, put it back unless you want the sugar.
Why a Dry Wine Can Taste Sweet
Sugar is only one of the things your tongue is reading. Four others push the same button, which is why two wines with identical numbers can taste nothing alike.
- Acidity. High acid makes a wine taste drier and lighter than the number suggests. Low acid does the opposite. This is the big one.
- Ripe fruit. A wave of jammy blackberry reads as sweetness even when the sugar is close to zero. Warm climate reds do this constantly.
- Oak. Barrels give vanilla and coconut notes, and your brain files those under sweet.
- Temperature. Warm wine tastes sweeter and flabbier. The same bottle, properly chilled, tastes tighter and drier.
So a big warm Shiraz with 2 grams of sugar can taste sweeter than a cold Riesling with 8. The trick is to stop reading the number in isolation. If you want the detail on how these things interact, we cover it in the guide to off-dry wine.
How the Sugar Ends Up in the Bottle
- The yeast gives up. Very ripe or shrivelled grapes carry so much sugar that the rising alcohol eventually stops the yeast working. Sauternes, icewine and dried grape wines all happen this way.
- The winemaker stops it. Chilling the ferment and filtering the yeast out leaves sugar behind on purpose. Moscato d’Asti is made like this. Adding grape spirit does the same job, which is how Port keeps its sweetness.
- Sweetening at the end. Some everyday wines have preserved grape juice added back before bottling to round them off.
How Much Sugar Is Actually in Your Glass
Grams per litre sounds alarming until you do the sum on a real pour. A standard 150 millilitre glass is 15 per cent of a litre, so you multiply the RS figure by 0.15.
- A dry wine at 4 grams a litre gives you about 0.6 grams of sugar a glass.
- An off-dry Riesling at 12 grams a litre gives you about 1.8 grams.
- A sweet wine at 45 grams a litre gives you just under 7 grams, though most people drink it in 60 millilitre pours, which brings it back under 3.
In almost every wine that is not a dessert wine, the alcohol carries far more energy than the sugar does. The wine calorie calculator splits the two out for any bottle you feed it.
Try One and Taste the Difference
The fastest way to understand residual sugar is to drink something with plenty of it beside something with none. Moscato is the easy example, because the fermentation is stopped on purpose and the sugar is the entire point.
Saint Valentine Reserve Moscato 2024
A fresh, grapey Moscato with the fermentation halted early to keep the sugar in the bottle. Pour it beside a dry Riesling and the gap between 4 grams and 100 stops being an abstraction. Stock checked live on the day this was written.
- A clear and cheap lesson in what residual sugar does to a wine
- Light in alcohol, so it works as an afternoon glass rather than a nightcap
- Genuinely good with fresh fruit, pavlova or a strong blue cheese
- Sweet by design, so no use at all if you wanted a dry white
- Drink it cold and drink it young
Frequently Asked Questions
What does RS mean on a wine label or tech sheet?
RS is simply short for residual sugar. It is written in grams per litre, sometimes shortened to g/l. If a tech sheet says RS 3.2 g/l, that wine is dry.
How much sugar is in a dry wine?
Up to 4 grams a litre by the European definition, and often only 1 to 2 in practice. A wine almost never reaches zero, because a small amount of sugar cannot be fermented by yeast at all.
Is Brut or Extra Dry sweeter?
Extra Dry is sweeter. Brut runs up to 12 grams a litre and Extra Dry sits between 12 and 17. The naming is a historical leftover, not a description.
Why does my dry red taste sweet?
Almost certainly ripe fruit, oak and serving temperature rather than sugar. Try the same bottle ten minutes out of the fridge and it will taste noticeably drier.
Does less residual sugar mean fewer calories?
A little, but alcohol is the bigger contributor in most wines, and a drier wine is often the stronger one. The calculator shows you the split.
Where do these sugar categories come from?
They are set in European labelling rules, which tie each term to a measured range. Decanter lays the ranges out clearly in this explainer on residual sugar, and the same words appear on plenty of Australian bottles made for export.
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