An image forming apparatus , comprising: an in-situ refillable upper toner hopper ; a developer to develop an electrostatic latent image formed on a photosensitive drum , using toner, the developer comprising a lower toner hopper to receive the toner from the in-situ refillable upper toner hopper via a mechanical toner transport ; a cleaning member to remove waste toner from a surface of the photosensitive drum ; a waste toner hopper to collect the waste toner from the cleaning member ; non-volatile memory ; and at least one processor , in electrical communication with the non-volatile memory , to: count a number of times the lower toner hopper receives toner from the in-situ refillable upper toner hopper , calculate an estimate of toner volume transferred from the lower toner hopper to the surface of the photosensitive drum , determine an amount of toner consumed from the in-situ refillable upper toner hopper based on the number of times the lower toner hopper receives toner from the in-situ refillable upper toner hopper and the estimate of toner volume transferred from the lower toner hopper to the surface of the photosensitive drum , and generate an upper toner hopper refill notification when the amount of toner consumed from the in-situ refillable upper toner hopper is determined to exceed a threshold value. an in-situ refillable upper toner hopper ; a developer to develop an electrostatic latent image formed on a photosensitive drum , using toner, the developer comprising a lower toner hopper to receive the toner from the in-situ refillable upper toner hopper via a mechanical toner transport ; a cleaning member to remove waste toner from a surface of the photosensitive drum ; a waste toner hopper to collect the waste toner from the cleaning member ; non-volatile memory ; and at least one processor , in electrical communication with the non-volatile memory , to: count a number of times the lower toner hopper receives toner from the in-situ refillable upper toner hopper , calculate an estimate of toner volume transferred from the lower toner hopper to the surface of the photosensitive drum , determine an amount of toner consumed from the in-situ refillable upper toner hopper based on the number of times the lower toner hopper receives toner from the in-situ refillable upper toner hopper and the estimate of toner volume transferred from the lower toner hopper to the surface of the photosensitive drum , and generate an upper toner hopper refill notification when the amount of toner consumed from the in-situ refillable upper toner hopper is determined to exceed a threshold value. count a number of times the lower toner hopper receives toner from the in-situ refillable upper toner hopper , calculate an estimate of toner volume transferred from the lower toner hopper to the surface of the photosensitive drum , determine an amount of toner consumed from the in-situ refillable upper toner hopper based on the number of times the lower toner hopper receives toner from the in-situ refillable upper toner hopper and the estimate of toner volume transferred from the lower toner hopper to the surface of the photosensitive drum , and generate an upper toner hopper refill notification when the amount of toner consumed from the in-situ refillable upper toner hopper is determined to exceed a threshold value. <EOS>