What is 305/70R17 in inches?

Twelve inches of section width, in metric

12.01 in. Metric codes climb in 10 mm and 20 mm steps and this is where they cross a threshold that flotation sizing reaches in a single named step: 305 mm is the first width here that converts to more than twelve inches. Everything narrower — the 285s and 295s — stays in the elevens.

It lives in a gap nothing else occupies

33.81 in falls between the sizes people actually name. It is 0.81 in taller than a flotation 33 and 1.19 in shorter than a 35, so neither nickname fits and nobody calls it a 34 either, even though that is the nearest whole inch. Sizes without a nickname get discussed less than their fitment merits, and this is one of them.

Between the 295 and the 315

• 295/70R17 — 33.26 in, 0.55 in shorter
• 315/70R17 — 34.36 in, 0.55 in taller

The 70-series on a 17-inch wheel produces an unusually regular ladder: each 10 mm of section adds 0.55 in of diameter, because the aspect ratio converts width into sidewall at a fixed rate and the sidewall counts twice. Three sizes, evenly spaced, which is rarer than it sounds.

Still narrower than a flotation tire of any height

12.01 in of section against the 12.50 in that 33x12.50R17, 35x12.50R17 and 37x12.50R17 all share: 0.49 in narrower than every one of them, regardless of how tall they are. Flotation sizing holds width constant across a whole family of diameters, which is precisely what metric sizing cannot do, because in metric the width is the thing that generates the height.

Sidewall and rotations

8.41 in of sidewall, and 596.5 revolutions per mile. That rotation count sits between the flotation 33 at 611.2 and the 35 at 576.2, exactly as the diameter does — a reminder that the count is nothing more than the diameter turned upside down. Load a comparison against either to see the figures worked through, and the revolutions per mile reference for where 63,360 comes into it.