To know not only the presence of recording material but also the residual quantity thereof by calculating the number of printable sheets based on the consumption of the recording material required for printing a specified volume of print data and the measured residual quantity of the recording material.

A calculating section 106 counts the number of printing dots based on a dot data (a dot to be printed is represented by 1 and a dot not to be printed is represented by 0, for example) stored in a print buffer 104. The count is multiplied by ink consumption per dot to calculate ink consumption required for printing a print data. The calculating section 106 subtracts the ink consumption from the previous residual quantity of ink to determine a current residual quantity of ink. Finally, the calculating section 106 calculates the number of printable sheets using the accumulated ink consumption and the current ink consumption.