Remove the wheel from the vehicle if needed
Place the wheel on a flat, level surface
Measure the distance between the inside edges of the rim flanges
Do not include the outer lips or decorative edges
Use a tape measure, ruler, or caliper for accuracy
Measure straight across the wheel from bead seat to bead seat
Record the measurement in inches or millimeters
Check the wheel markings for the listed width if available
Verify whether the width is measured at the bead seat or overall outer width