What is 275/70R18 in inches?
Answer
33.16 in tall
275/70R18 is 33.16 in in overall diameter and 10.83 in in section width, on a 18 in wheel. Its sidewall is 7.58 in tall.
The working
- Overall diameter
- 33.16 in
- Section width
- 10.83 in
- Sidewall height
- 7.58 in
- Circumference
- 104.2 in
- Revolutions per mile
- 608.3
- Nearest whole-inch call size
- 33 in
A 33 from the other side
Nearly every metric size marketed as a 33 measures under 33.00 in. This one measures 33.16 in and goes past it. It is a small distinction and a rare one: if a build was planned around "33s" using a 285/70R17 at 32.71 in as the reference, swapping to this size adds nearly half an inch that was not in the plan.
Identical sidewall to the 17-inch version, one inch of extra wheel
275/70R17 has a 7.58 in sidewall. So does 275/70R18. That is not a coincidence — sidewall height is computed from the section width and the aspect ratio alone, and the rim diameter never enters the calculation. Change the wheel and the sidewall is untouched; the whole difference lands in the overall diameter, which goes from 32.16 in to 33.16 in. Exactly 1.00 in, exactly the wheel.
Where the width sits
10.83 in of section is narrow for a 33-inch tire — 1.67 in less than a 33x12.50R18 on the same wheel, which is a very large gap for two tires of the same nominal height. That is the single most useful number on this page: it means the two sizes make very different demands on the space beside a wheel while making near-identical demands on the space above it. Whether either clears a given arch is a measurement on that vehicle, but the 1.67 in is where the two differ, and it is where to measure.
Written out in imperial, and where it lands
The exact flotation description of this tire is 33.16x10.83R18, which no manufacturer produces — the notation has no half-inch step at 10.83 and no fractional diameter. Going the other way on the same wheel, 285/70R18 reaches 33.71 in with a 11.22 in section, so this size is the narrow option in a pair that is only just over half an inch apart in height.
The nearly identical alternative on a bigger wheel
Move up to a 20-inch rim at the same 275 mm section and 275/60R20 arrives at 32.99 in, sitting 0.17 in under this tire while trading 7.58 in of sidewall for 6.50. Geometrically the pair are interchangeable — 0.50% apart on a speedometer — and as objects they are nothing alike. The comparison drawing makes the reason obvious in one glance.