What is 285/70R17 in imperial sizing?

The closest match on height and the closest match on width are different tires

Imperial flotation codes come in whole-inch diameters and half-inch widths, so a metric size almost never lands on one. 285/70R17 works out to 32.71 in tall and 11.22 in wide, and those two figures round toward different products:

• 33x12.50R17 — 0.29 in taller, 1.28 in wider.
• 33x10.50R17 — 0.29 in taller, 0.72 in narrower.
• 32x11.50R17 — 0.71 in shorter, 0.28 in wider.

The third is by far the nearest on section width and the furthest on height. There is no single flotation size that is closest on both, which is the whole difficulty with this conversion.

The first two tie exactly, and that is structural rather than coincidental: flotation heights are quoted in whole inches, so every 33-something on a 17-inch wheel measures the same 33.00 in. Once a candidate list has been sorted by height it stops discriminating, and width is the only field left to choose on.

Why the grid is so coarse

A metric code can express any width in single millimetres and any aspect ratio in whole percentage points, which is why 11.22 in exists as a section width at all. Flotation notation was never built for that resolution: it names the diameter to the inch and the width to the half inch, and everything else is inferred. Converting downward into it always loses information.

What "equivalent" ends up meaning

In practice a fitment guide listing 33x12.50R17 as the imperial equivalent of 285/70R17 is matching height and ignoring an inch and a quarter of width, because height is what changes the speedometer and the gearing. That is a defensible choice and it is a choice, not a fact. Load the converter with this size to see the ranked list with both differences shown, and the notation reference explains which dimension each system fixes.

The exact answer, for completeness

32.71x11.22R17. Nobody makes it and no shop will order it, but it is the number every rounded answer on this page is rounded from.