Calculate differences in both tire size and wheel offset positioning for new wheel and tire setups. View the results with our visualizer and compare key measurements for accurate fitments.
Use our wheel offset calculator to calculate the difference in wheel and tire position when switching to different wheel offsets/backspacing or tire size.
Input your current tire and wheel setup including wheel offset, then add the new setup to compare positioning.
The visualizer will show the new setup outlined in orange, the side by side comparison of the two sizes and the changes to speedometer readings.
Also calculated are the differences in tire diameter, width, aspect ratio, and revolutions per mile along with changes to key measurement differences.
The distance from the top of the tire to the fender well, the inside of the tire to the vehicle's suspension and frame, and the poke of the tire are all shown.
You may also click on the Offset Converter tab to convert wheel offset to backspacing and vice versa. Just select a wheel size and start typing either offset or backspacing and the equivalent will be shown. We only use an offset input for the calculator, so if you know the backspacing and not the offset simply convert it and input the offset into the field. We do this because offset does not require a wheel width to determine the correct mounting surface of the wheel.
Wheel width will effect the tire width by 1/10" on each side for ever 1/2" change in wheel width. This is a small concern unless you plan on running wheel widths that are well outside the manufacturer's recommended range. If you plan on stretching the tires, or running wheel widths that are wider than the width of the tire then you will need to keep in mind that the visualizer is showing tire position not wheel position. In this case the wheel may be closer/further than the calculated distances of key measurements.
Wheel offset is the distance in millimeters from the center line of the wheel to the mounting surface. If the mounting surface is closer to the face of the wheel it is known to have a positive offset and if the mounting point is closer to the inside of the wheel it has a negative offset. Center or no offset is when the mounting point is directly on the centerline of the wheel.
Wheel backspacing is the distance in inches from the mounting surface to the inside edge of the wheel. A wheel's width is from the mounting points of the tire beads, therefore the measured width of a wheel from outside edge to outside edge is about an inch wider than spec. An 8" wheel will measure 9" from side to side, this makes converting offset to backspacing not so straight forward. If an 8" wheel has a center offset the backspacing is not 4", it is actually 4.5".