There is a great website with a set of calculators that can make the chemistry involved in making wine much easier for the average home wine-maker. The site is called VinoEnology and includes a separate page with a very useful set of calculators for determining additions and dilution rates for sugar-water, acid blend, and sulfites among others.
Correct Acid or pH levels along with the proper use of sulfite is a critical aspect in producing consistently good wine and preventing spoilage. Chaptalization is the process of adding sugar to must or juice before fermentation. This is very important for fruit and berry wine-makers as these ingredients, although very high in flavor, are usually too low in sugar and the volume of juice required to produce a palatable wine-like fermented beverage. Dilution calculation is also necessary when using grape juice concentrates for the home wine-maker.
This calculator is very easy to use with complete instructions. Testing for acid level is a necessary step to determine the amount needed. Most hobby wine-makers learn to do very simple acid titration analysis with kits available at any good hobby wine-making supplier. A laboratory grade pH meter is another method but these are quite expensive and require accurate calibration.
All other calculators on this site are just as easy to use and can be very helpful. In addition all of these calculators are available as an App for your iPhone or Android.