Isobaric molar heat capacities of 1-ethyl-3-methylimidazolium acetate ([C(1)C(2)Im][OAc]) and 1-hexy1-3-methylimidazolium acetate ([C(1)C(6)Im][OAc]) were measured in the temperature range T = (303-393) K and at pressures up to 16 MPa. The relative expanded uncertainty of the isobaric molar heat capacity is estimated to be less than 1%. Based on the experimental data in our work and from literature, the isobaric molar heat capacities of [C(1)C(2)Im][OAc] and [C(1)C(6)Im][OAc] were found to rise with the increasing temperature and the carbon atoms number on the cations, and fall with the increasing pressure. Correlations based on the experimental data were promoted to evaluate the heat capacity of [C(1)C(2)Im][OAc] and [C(1)C(6)Im][OAc], the absolute relative deviation between calculation and experimental data is less than 1%. (C) 2016 Elsevier B.V. All rights reserved.