A method of estimating an amount of an unconsumed part of a recording material wrapped on a core of a roll is implemented as an application program for an electronic device having a camera. A storage device stores reference data about the roll and the recording material in an unconsumed state. The method includes taking a picture of the recording material and the core with a camera, deriving from the picture characteristics of a first and second number of pixels representing the core and the unconsumed part of the recording material, respectively, requesting from a user an identification of the roll and the recording material, receiving the identification, matching the identification with the reference data, and calculating the amount of the unconsumed part of the recording material by means of the matched reference data and the characteristics of the first and second numbers of pixels.