Tannic acid is a determined cast of tannin, a type of polyphenol. Its weak acidity (pKa all 6) is rightful to the numerous phenol groups in the structure. The chemical formula on commercial tannic acid is often specified as C76H52O46, which corresponds with decagalloyl glucose, but in in reality it is a hodgepodge of polygalloyl glucoses or polygalloyl quinic acid esters with the number of galloyl moieties per molecule ranging from 2 up to 12 depending on the plant source second-hand to extort the tannic acid. Commercial tannic acid is usually extracted from any of the following plant parts: Tara pods (Caesalpinia spinosa), gallnuts from Rhus semialata or Quercus infectoria or Sicilian sumac leaves (Rhus coriaria).

According to the definitions provided in alien references such as global pharmacopoeia, Subsistence Chemicals Codex and FAO-WHO tannic acid paper just tannins sourced from the above-mentioned plants can be considered as tannic acid. Off extracts from chestnut or oak wood are also described as tannic acid but this is an faulty expend of the term. It is a yellow to taper brown amorphous powder.