Free tools for winemakers
Water addback calculator
Water to bring a must down to a lower sugar or alcohol
Water to add
Type the volume, the current reading and the target.
To see the acidity after the water.
Before fermentation only. Once fermentation starts, alcohol throws the reading off: a hydrometer shows less sugar than is really there, a refractometer more.
Past the US limit. In the US, water may not take juice below 22 °Brix, or lower juice that is already under 23 °Brix by more than 1 °Brix.
Check your local rules. The EU does not allow adding water to must or wine, so it can’t be used to lower sugar. The only exception (Regulation (EU) No 1308/2013, Annex VIII) is a specific technical need, such as dissolving an additive. The US allows it only down to 22 °Brix, and by at most 1 °Brix when the juice is already under 23 °Brix (27 CFR 24.176). Australia allows it down to 13.5 °Baumé (FSANZ Standard 4.5.1). Check your local rules before you add water.
How do we calculate this?
The exact formulas used in this tab:
What this calculator does
Works out how much water to stir into must to bring its sugar down to a target. It is for must before fermentation.
- The target can be a sugar reading (Brix, SG, Baumé, Oechsle or KMW) or a potential alcohol.
- It shows the new volume and, if you type the acidity (TA), the acidity after the water, which drops by the same ratio.
- It doesn’t tell you whether adding water is allowed where you make wine.
The formula
S1, S2 = sugar (g/L) now and at the target = Brix × 10 × SGTarget alcohol → target Brix = alcohol % ÷ 0.59Water (L) = V × (S1 ÷ S2 − 1)New volume = V + waterNew TA = TA × V ÷ new volumeSource: dilution (S1 × V = S2 × new volume); AWRI, Winemaking treatment – Water addition
Worked example
- 1,000 L of must
- Now: 26 °Bx
- Target: 24 °Bx
- Acidity: 6 g/L
- The sugar stays the same, so the volume grows by 288.75 g/L ÷ 264.31 g/L = 1.09247
- How much water 1,000 × (1.09247 − 1) = 92.47 L
- New volume 1,000 + 92.47 = 1,092.5 L
- Potential alcohol, before and after 15.3 % vol → 14.2 % vol
- Acidity after 6 × 1,000 ÷ 1,092.47 = 5.49 g/L
Add 92.47 L of water
Questions
Am I allowed to add water?
It depends on where you make wine. The EU does not allow adding water to must or wine, so it can’t be used to lower sugar; the only exception is a specific technical need, such as dissolving an additive. The US allows it only down to 22 °Brix, and by at most 1 °Brix when the juice is already under 23 °Brix; the calculator warns when a target passes that. Australia allows it down to 13.5 °Baumé. Check your local rules first; the calculator only does the arithmetic.
EU: Regulation (EU) No 1308/2013, Annex VIII. US: 27 CFR 24.176. Australia: FSANZ Standard 4.5.1.
Why does the acidity drop?
Water dilutes the acid just as it dilutes the sugar. The amount of acid stays the same while the volume grows, so TA falls by the same ratio, here 6 × 1000 ÷ 1092.47 = 5.49 g/L. pH changes too, but not by a simple sum. Mix well, then measure Brix, pH and TA again before adjusting anything, as the AWRI advises.
Why does it work in g/L rather than Brix?
Brix is a share by weight, and water is added by volume. Grams of sugar per liter change in exact proportion to the volume. So the calculator first turns both readings into g/L, as the formula above shows. Adding water leaves the sugar in the tank the same and only makes the volume bigger.
Can I aim for an alcohol level instead?
Yes. Choose “Target alcohol” and type it, for example 14.5 % vol. The calculator turns it into a sugar target by dividing by 0.59. The 0.59 factor is an estimate: the alcohol you actually get depends on the yeast and the fermentation.