Branching in polymers is an important feature that plays a role in their applications. The degree of branching (DB) has been quantified in several polymers using NMR spectroscopy. In this work, the DB of poly(acrylic acid), PAA, was quantified. The precision and accuracy of DB quantification in this polymer has been assessed for the first time. Incomplete dissolution lowers the accuracy of DB. Moisture content, chain end, and impurities have to be taken into account to assess the solubility correctly. The incomplete solubility may be partially due to some clustering and it might for example explain the notable inaccuracy of the molecular weights determined by SEC for PAA. The error introduced during data treatment in NMR spectroscopy affects the precision of DB. This study enables the design of the best approach for a precise and accurate DB quantification not only for PAA but also for other branched polymers. An accurate DB increases the knowledge of the polymer structure, enhancing the capacity to tailor PAA structures for properties desired in many applications.