Homemade Vinegar Acidity
ANSWER - Store-bought vinegar is standardized to at least 5% acetic acid or about pH 3 (read the label).
The acidity of homemade vinegar is variable because of variation in characteristics of the starting material. It could contain more or less acid.
To assure a safe product when pickling or canning with vinegar, the USDA Complete Guide to Home Canning recommends using vinegar of at least 5% acidity. Homemade vinegars should not be used in canning recipes.