A method for transfer voltage adjustment for use in an image forming apparatus includes forming first and second halftone reference patterns, transferring the halftone reference patterns to a transfer element at respective first and second saturated transfer voltages, calculating first and second amounts of adhering toner on the transfer element, and setting up a saturated transfer voltage based on the first and second transfer voltages, the amounts of adhering toner, and a saturated amount of adhering toner obtained from stored data.