How to use the tartaric acid addition calculator
- Enter the batch volume and choose the unit.
- Enter the current titratable acidity from your test and the acidity you want, both in g/L as tartaric.
- Choose the acid you will add: tartaric, malic, or citric in its anhydrous or monohydrate form.
- Read the grams of acid to add. Add it in stages and retest.
Formula
Acidity to add (as tartaric) = target - current, in g/L
Grams = acidity to add x liters x factor
Factor = (molar mass / acidic hydrogens) of the acid divided by (molar mass / acidic hydrogens) of tartaric acid
Tartaric 150.09 / 2 = 75.04 g per equivalent
The factors are 1 for tartaric, 0.8934 for malic, 0.8534 for anhydrous citric and 0.9334 for citric monohydrate.
Raise a 5 gallon batch by 1 g/L
A 5 US gallon batch is 18.93 liters. Raising the acidity from 5.5 to 6.5 g/L as tartaric means adding 1 g/L, which is 18.9 g of tartaric acid.
With malic acid the same change takes 18.9 x 0.8934 = 16.9 g, and with anhydrous citric acid 16.2 g. For a 23 liter batch raised from 4.8 to 6 g/L with malic acid the amount is 24.7 g.
Titratable acidity in plain terms
Titratable acidity measures the total acid in a wine or must by how much base it takes to neutralize it. It is reported as if all the acid were tartaric acid, in grams per liter, so that different batches can be compared. Another acid with a lighter molecule carries more acid per gram, which is why it takes less malic or citric acid than tartaric to move the number the same amount.
The factor on this page comes from equivalent weights. Each acid has a molar mass and a number of hydrogens that can be given up. Dividing the molar mass by that number gives the grams that neutralize one mole of base, and the ratio to tartaric acid is the factor.
Adjusting with care
The taste and stability of a wine depend on pH as much as on acidity, and an addition changes both. Acids differ in how they taste, and citric acid can be turned into other compounds by microbes in a wine that goes through a second fermentation. Many winemakers add acid in small steps and taste before going on.
This page is informational and works out additions only. It does not lower acidity. Follow your recipe and the advice of your supplier, and test a small sample before treating the whole batch.
Assumptions and limits
- Acidity is entered in g/L as tartaric, which is how most test kits report it.
- The factors use standard atomic masses (carbon 12.011, hydrogen 1.008, oxygen 15.999).
- The acid dissolves completely and the volume stays the same.
- Nothing is uploaded.
Frequently asked questions
Why is the malic acid amount smaller?
Malic acid has a lighter molecule for the same number of acidic hydrogens, so a gram gives more acid than a gram of tartaric acid.
Will this change pH?
Yes. Adding acid lowers pH, but by how much depends on the buffering of the batch. Measure after you add.
Can I lower acidity with this tool?
No. The target must be above the current value. Lowering acidity uses other methods, such as adding a base.
Which acid should I choose?
Use the one your recipe calls for. Tartaric is the standard for wine, and malic and citric change the taste in different ways.