Rim Width Range Calculator

How we calculate

Enter one tire size in metric notation such as 225/50R17 or flotation notation such as 33x12.50R17. The calculator returns an approximate narrowest and widest rim width in inches, rounded to the nearest half inch, plus the same range in millimeters. Rim width here means the distance between the bead seats, which is the width marked on the wheel, not the outside edge-to-edge width.

We did not find a complete public table of approved rim widths that we can cite. Full ranges are published in paid standards from the Tire and Rim Association and ETRTO, and each tire maker lists its own range. This tool therefore uses an approximation rule and labels the result as an approximation. For aspect ratios of 50 and above, the range is 0.70 to 0.90 times the section width. For aspect ratios below 50, it is 0.80 to 1.00 times the section width. Section width in inches is the metric width divided by 25.4.

We checked the rule against the two published examples cited in our rim width guide. Tire Rack lists 5.5 to 7.5 inches for P205/60R15. The section width is 205 / 25.4 = 8.07 inches, so 0.70 x 8.07 = 5.65, rounded to 5.5, and 0.90 x 8.07 = 7.26, rounded to 7.5. Discount Tire lists 7.5 to 9.5 inches for 245/45R20. The section width is 9.65 inches, so 0.80 x 9.65 = 7.72, rounded to 7.5, and 1.00 x 9.65 is rounded to 9.5. Both match, but two examples do not prove the rule for every size.

The result is a starting point for a conversation, not an approved range. A tire mounted outside the range its maker approves can wear unevenly and handle poorly. Section width also changes with the rim: Tire Rack notes about 0.2 inch of section width for every half inch of rim width. Before buying wheels or tires, read the rim width range in the specification of the exact tire model, or ask the tire maker or an installer.

Frequently asked questions