Wine Residual Sugar Calculator
Calculate residual sugar (RS) in wine from specific gravity readings.
Determine wine sweetness level from grams per liter of residual sugar.
Residual sugar (RS) is the sugar remaining in a wine after fermentation is complete. It decides whether a wine is dry, off-dry, semi-sweet or sweet, and it drives how the wine tastes, what it pairs with, and how long it keeps.
The formula:
RS (g/L) = (Final gravity − Dry baseline) × 1000 × 2.6
One gravity point (0.001) is worth roughly 2.6 g/L of sugar. That falls out of two figures every winemaker already knows: one degree Brix is about 10 g/L of sugar, and one degree Brix moves specific gravity by about 0.004. Divide and you get 2.5 to 2.6 g/L per point.
The baseline is the part people get wrong. Sugar is not the only thing in the glass. Alcohol is lighter than water, so a completely dry wine lands below 1.000, and how far below depends on its strength. Measuring against 1.000 instead of the real dry baseline under-reports every sweet wine badly. Pick the baseline that matches your alcohol:
| Finished alcohol | Dry baseline (SG) |
|---|---|
| Under 11% ABV | 0.996 |
| 11–13% ABV (most table wine) | 0.994 |
| 13–15% ABV | 0.992 |
Wine sweetness classification by RS:
| Category | RS (g/L) | RS (%) |
|---|---|---|
| Bone dry | 0–1 g/L | 0–0.1% |
| Dry | 1–9 g/L | 0.1–0.9% |
| Off-dry | 9–18 g/L | 0.9–1.8% |
| Semi-sweet | 18–45 g/L | 1.8–4.5% |
| Sweet | 45–120 g/L | 4.5–12% |
| Dessert wine | 120+ g/L | 12%+ |
Worked example: A 12% Riesling whose fermentation was chilled to a stop, finishing at SG 1.004: RS = (1.004 − 0.994) × 1000 × 2.6 = 10 × 2.6 = 26 g/L, so semi-sweet
How much to trust it. A hydrometer resolves about half a gravity point, which is ±1.3 g/L before you even consider whether the baseline was right, and the baseline itself is a guess worth several g/L. That is fine for deciding dry from off-dry and useless for label compliance. A refractometer is worse, not better, after fermentation. Alcohol bends light far more than sugar does, so the reading is meaningless without a correction formula. For a real number use a Clinitest tablet, an enzymatic kit, or a commercial lab.
Balancing sweetness with acidity: Higher RS needs higher acidity or the wine turns cloying. German Riesling manages this naturally, carrying enough tartaric acid to hold up 40 g/L of sugar without tasting sweet. Perceived sweetness falls sharply as pH drops: a 15 g/L wine at pH 3.0 tastes drier than the same sugar at pH 3.5.
Stabilization: any wine bottled above about 2 g/L of RS has to be stabilised, or a surviving yeast cell will restart in the bottle and either push the cork or burst it. The home route is potassium sorbate plus enough free SO2 to back it up, since sorbate does almost nothing on its own. The commercial route is sterile filtration at 0.45 micron. Note that cold stabilisation is not one of the options here: it drops tartrate crystals out, which is a clarity and mouthfeel job, and it does nothing whatever to yeast.
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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