Nobody manufactures a tire labelled "33 inch" in metric notation. Several metric sizes land near 33 inches and get called 33s, and choosing between them is a width and wheel decision rather than a height one.
The conversion arithmetic is on the tire size conversion page.
The candidates
| Metric size | Overall diameter | Off 33″ | Section width |
|---|---|---|---|
| 255/80R17 | 33.06″ | +0.06″ | 10.04″ |
| 255/85R16 | 33.07″ | +0.07″ | 10.04″ |
| 275/70R18 | 33.16″ | +0.16″ | 10.83″ |
| 285/75R16 | 32.83″ | −0.17″ | 11.22″ |
| 305/70R16 | 32.81″ | −0.19″ | 12.01″ |
| 295/70R17 | 33.26″ | +0.26″ | 11.61″ |
| 285/70R17 | 32.71″ | −0.29″ | 11.22″ |
Height spread: 0.55 inches. Width spread: 1.97 inches. All seven are "33s" in conversation, and they are much more different from each other in width than in height.
That is the practical headline: if you are choosing among these, you are choosing a width and a wheel size, and the height is roughly settled either way.
Narrow or wide
The two ends of that table behave quite differently.
255/85R16 — tall and narrow, on a small wheel. Lots of sidewall, which means compliance off-road and the ability to run low pressures without unseating. Cuts through soft ground rather than floating on it. Minimal fender clearance issues. Often preferred by people who actually go far from pavement.
305/70R16 — wide, on the same small wheel. More contact patch, better flotation on sand, more aggressive appearance, and considerably more likely to rub at full lock or need fender trimming.
275/70R18 — the modern compromise, on a large wheel with a shorter sidewall. Better on-road manners, less sidewall to protect the rim, and less able to be aired down.
None of those is the right answer in general. They are different tires that happen to be the same height.
What actually decides it
The wheel you already have. If you have 17-inch wheels, the 16- and 18-inch options are irrelevant unless you are buying wheels too. This eliminates most of the table immediately.
Clearance at full lock, compressed. Not the gap when parked. Width and offset together decide whether the tire meets the fender liner when you turn into a driveway with the suspension loaded.
Load index. Bigger tires are heavier and are frequently fitted to vehicles that tow or carry load. The load index has to meet the vehicle placard, and it is easy to lose load rating while chasing size.
Availability. Some of these sizes have five options across all manufacturers and some have fifty. The narrow tall sizes in particular are specialist.
The gearing consequence
Going from a factory 265/70R17 at 31.61 inches to any of these is a jump of about 4 to 5 %:
| To | Diameter change | Indicated 60 mph is really |
|---|---|---|
| 285/70R17 | +3.5 % | 62.1 mph |
| 255/80R17 | +4.6 % | 62.8 mph |
| 295/70R17 | +5.2 % | 63.1 mph |
All of those are past the 3 % band where speedometer error stops being negligible. Recalibration is worth doing, and on a vehicle that tows, the effective gearing change is a real consideration rather than a curiosity — a taller tire makes the transmission work harder at the same road speed.
Measured versus nominal
Every diameter above is calculated from the nominal size. Actual tires run a few tenths either way, and aggressive off-road tread patterns often measure slightly larger than the calculation.
For a marginal fit, use the manufacturer's published measured diameter for the specific model. The difference between two 285/70R17 tires from different makers can be a quarter inch — which is most of the spread in the whole table above.
What this page does not cover
- Fitment approval. Nothing here says any of these will fit your vehicle.
- Lift requirements, trimming and suspension changes, which are vehicle-specific.
- Load index and speed rating must satisfy the vehicle placard — see reading a sidewall.
- Flotation sizes like 33×12.50R17 state the diameter directly and need no conversion at all.
Seven answers within half an inch of each other. Pick by wheel size and width, because the height decision is already made.