An image forming apparatus is provided that includes a detection unit to detect a measure of consumption of a second cartridge. A difference between toner amounts is acquired by subtracting a toner amount per unit area of a toner image corresponding to a maximum density image formed on a first image bearing member from a toner amount per unit area of a toner image corresponding to a maximum density image formed on a second image bearing member. When the detection unit detects a second measure of consumption that is in a consumed state more than a first measure of consumption, a control unit controls a first toner forming unit and a second toner forming unit so that a difference between toner amounts is greater than when the detection unit detects the first measure of consumption.