A calibration structure (10) for calibrating a flex fuel sensor (12) for a vehicle is provided. The flex fuel sensor has a first sensor electrode (14) and a second sensor electrode (16). The calibration structure includes a first electrode (30), a second electrode (36) spaced from and electrically insulated from the first electrode, and at least one capacitor (40), or at least one resistor (42), or at least one combination of a capacitor with a resistor, of a certain value electrically connected with the first and second electrodes. The first electrode (30) is constructed and arranged to contact the first sensor electrode (16) and the second electrode (36) is constructed and arranged to contact the second sensor electrode (14) to provide a known input value to the flex fuel sensor for calibration of the flex fuel sensor without the use of test liquids.