An image forming apparatus comprising: a print unit which includes a container containing a colorant and which is configured to perform a printing operation on one side of a sheet conveyed along a printing conveyance path; an inversion mechanism configured to receive the sheet from the print unit and send the sheet via an inversion conveyance path back to the print unit with the front and rear surfaces of the sheet inverted; a control unit configured to control the print unit and the inversion mechanism to perform a double-side printing operation, wherein first an operation of printing an image on one side of N non-printed sheets (N ≥ 1), respectively, is performed by the print unit to obtain N one-side printed sheets, and then thereafter an operation of printing images on an opposite side of M of the N one-side printed sheets, which are fed to the print unit with the front and rear surfaces of the sheet inverted by the inversion mechanism, using the colorant is performed by the print unit before another operation of printing on one side of a non-printed sheet by the print unit is performed, the double-side printing operation including a plurality of double-side printing methods in which at least one of N and M in one of the double-side printing methods is different from N or M, respectively, in another of the double-side printing methods; and a determination unit which is configured to determine whether an amount of the colorant remaining in the container is equal to or greater than a threshold value; wherein the control unit is configured to select one of the double-side printing methods and to control the print unit to perform the selected double-side printing method, characterized in that the control unit is configured to control the print unit and the inversion mechanism to perform a double-side printing operation according to a first double-side printing method, when the determination unit determines that the amount of the remaining colorant is equal to or greater than the threshold value, and when the determination unit determines that the amount of the remaining colorant is less than the threshold value, to perform a negative selection process of selecting a second double-side printing method satisfying at least one condition of a condition that N is smaller than that of the first double-side printing method and a condition that the number of opposite-side printed sheets M is greater than that of the first double-side printing method. a print unit which includes a container containing a colorant and which is configured to perform a printing operation on one side of a sheet conveyed along a printing conveyance path; an inversion mechanism configured to receive the sheet from the print unit and send the sheet via an inversion conveyance path back to the print unit with the front and rear surfaces of the sheet inverted; a control unit configured to control the print unit and the inversion mechanism to perform a double-side printing operation, wherein first an operation of printing an image on one side of N non-printed sheets (N ≥ 1), respectively, is performed by the print unit to obtain N one-side printed sheets, and then thereafter an operation of printing images on an opposite side of M of the N one-side printed sheets, which are fed to the print unit with the front and rear surfaces of the sheet inverted by the inversion mechanism, using the colorant is performed by the print unit before another operation of printing on one side of a non-printed sheet by the print unit is performed, the double-side printing operation including a plurality of double-side printing methods in which at least one of N and M in one of the double-side printing methods is different from N or M, respectively, in another of the double-side printing methods; and a determination unit which is configured to determine whether an amount of the colorant remaining in the container is equal to or greater than a threshold value; wherein the control unit is configured to select one of the double-side printing methods and to control the print unit to perform the selected double-side printing method, characterized in that the control unit is configured to control the print unit and the inversion mechanism to perform a double-side printing operation according to a first double-side printing method, when the determination unit determines that the amount of the remaining colorant is equal to or greater than the threshold value, and when the determination unit determines that the amount of the remaining colorant is less than the threshold value, to perform a negative selection process of selecting a second double-side printing method satisfying at least one condition of a condition that N is smaller than that of the first double-side printing method and a condition that the number of opposite-side printed sheets M is greater than that of the first double-side printing method.