A simply device was developed and tested. It is designed to measure the heat capacity of square plates with size similar to 30 x 30 mm, at room temperature. This device consumes permanent electric power. The heat losses to the surroundings are taken into account. A mathematical model, of this heat capacity meter, is described in the paper. The heat capacity of a sample is calculated as a difference between measured heat capacity (of heater and sample) and heat capacity of the heater only. The optimal size of a test body, and reference one, is so as the contact surface of the heater. (C) 2010 Elsevier Ltd. All rights reserved.