Steel pycnometers are used to determine density of liquids and gases at different temperatures and pressures. In order to determine this density with reliability, it is necessary to define the mass and the volume of this artifact with the best possible accuracy. This work proposes a methodology for calibrating this artifact, using the gravimetric method, in the pressure range from 1 bar (0.1 MPa) up to 96 bar (9.6 MPa), at the temperature of 20 °C, using Ethanol Pa (with 95% purity in volume). The results of uncertainty of volume for ambient conditions are shown here. The pycnometer volume equation was developed in the pressure range of 1 bar (0.1 MPa) up to 96 bar (9.6 MPa) for the temperature of 20 °C, whose uncertainty found was 0.055 cm3 (0.006%).