Quick answers
One question, one number, the working underneath, and a link into the tool with the same inputs already loaded.
Some questions do not need an article. "What is 285/70R17 in inches" has an answer that is one number long, and the useful thing a page can do is put that number at the top and then show its working.
Every number on every page in this section is computed when the site is built, from the same library the calculators use. None of it is typed in. That matters more here than anywhere else on the site: an answer page exists to state a figure, so a figure that had been transcribed by hand would be the one thing capable of making the page worthless.
How to read one
The answer is first, in large type. Under it is a sentence saying where the number came from — which inputs, which arithmetic. Under that is the working: the intermediate values, so you can see the step that surprised you rather than taking the result on faith.
At the bottom of each is a link into the relevant calculator with the same inputs already loaded, because the second question is almost always "and what about this other size".
Why the tall-tire answers give a range
Questions like "how tall is a 33 inch tire" are answered with a range rather than a single figure, because that is the truthful answer. A "33" is a category of tires whose geometric diameters differ by most of an inch, and the page lists the specific sizes and what each one actually measures.
Giving a single number there would be tidier and would be wrong. The whole reason people search that phrase is that they have found two tires both described as 33s and noticed they are not the same, and a page confirming the difference is more use than one papering over it.
What these pages will not do
They will not tell you whether a size fits your vehicle. Every one of them ends at the arithmetic, because clearance, load rating and road-legality are properties of your specific vehicle and your jurisdiction rather than of a size code.
That boundary is why these pages can be short and exact. A question with one correct answer gets one; a question with fifty variables gets pointed somewhere better.
If your question is not here
Use the calculator the nearest answer page links to. The answer layer covers the questions that recur often enough to be worth a page of their own, and the tools cover everything else — including every size pairing, every axle ratio, and every service description.
- What is 285/70R17 in inches?What is 285/70R17 in inches?285/70R17 is 32.71 inches tall and 11.22 inches wide, with a 7.85 inch sidewall. Here is the arithmetic, and why it is not quite the 33 it is sold as.
- What is 265/70R17 in inches?What is 265/70R17 in inches?265/70R17 comes out at 31.61 inches tall and 10.43 inches wide. It is the truck size that gets called a 31 by some people and a 32 by others.
- What is 275/60R20 in inches?What is 275/60R20 in inches?275/60R20 computes to 32.99 inches tall — one hundredth of an inch under a genuine 33 — and 10.83 inches wide, which is 1.67 inches narrower than one.
- What is 255/75R17 in inches?What is 255/75R17 in inches?32.06 inches tall, 10.04 inches wide, 7.53 inches of sidewall. An honest 32 — and one of three codes on three different wheels that land on the same height.
- What is 245/75R16 in inches?What is 245/75R16 in inches?30.47 inches tall and 9.65 inches wide. Routinely sold and discussed as a 31, it is more than half an inch short of one — among the looser labels in truck sizing.
- What is 285/75R16 in inches?What is 285/75R16 in inches?32.83 inches tall on an 8.42 inch sidewall — the most rubber between rim and road of any common metric size, and 0.17 inches short of a flotation 33.
- What is 275/65R18 in inches?What is 275/65R18 in inches?32.07 inches tall and 10.83 inches wide, on a 7.04 inch sidewall — five aspect points and 1.08 inches below the 275/70R18 that shares its wheel.
- What is 315/70R17 in inches?What is 315/70R17 in inches?12.40 inches of section width and 34.36 inches of diameter. The width is a tenth of an inch off the flotation standard, which is why this size substitutes for a 35.
- What is 235/85R16 in inches?What is 235/85R16 in inches?31.73 inches tall on a section only 9.25 inches wide, with a 7.86 inch sidewall — the tallest aspect ratio still in ordinary production.
- What is 265/65R17 in inches?What is 265/65R17 in inches?30.56 inches — shorter than most people expect from a 265, and exactly 1.04 inches under a 265/70R17 of identical width on the identical wheel.
- What is 275/70R18 in inches?What is 275/70R18 in inches?33.16 inches — a 33 that overshoots rather than falls short — with 10.83 inches of section and a 7.58 inch sidewall identical to a 275/70R17's.
- What is 225/45R17 in inches?What is 225/45R17 in inches?24.97 inches overall on a 3.99 inch sidewall — a hair under four inches of rubber between rim and road, with the wheel taking up more than two-thirds of the tire.
- What is 205/55R16 in inches?What is 205/55R16 in inches?24.88 inches of overall diameter, 8.07 inches of section width, 4.44 inches of sidewall — and slightly shorter than the 195/65R15 it usually replaces.
- What is 195/65R15 in inches?What is 195/65R15 in inches?24.98 inches tall and 7.68 inches wide, with a 4.99 inch sidewall. Two hundredths under 25 inches, and within a hundredth of a 225/45R17.
- What is 265/75R16 in inches?What is 265/75R16 in inches?31.65 inches tall, 10.43 inches wide, on a 7.82 inch sidewall — the size that keeps a 16-inch wheel competitive with the 17s that replaced it.
- What is 305/70R17 in inches?What is 305/70R17 in inches?33.81 inches tall and 12.01 inches wide — the first metric size in this catalogue to pass twelve inches of section, sitting in the gap between the 33s and the 35s.
- What is 285/65R20 in inches?What is 285/65R20 in inches?34.59 inches tall and 11.22 inches wide, on a 7.29 inch sidewall. The wheel, not the rubber, is what makes this one of the tallest factory-fitted metric sizes.
- What is 275/55R20 in inches?What is 275/55R20 in inches?31.91 inches overall with only 5.95 inches of sidewall — a 20-inch wheel occupying nearly two-thirds of the tire, which is why the code looks so unlike a truck size.
- What is 33x12.50R17 in metric?What is 33x12.50R17 in metric?Exactly 318/64R17 — a size nobody manufactures. The closest metric tire genuinely sold on a 17-inch wheel is 255/80R17 at 33.06 in, and it is 2.46 in narrower.
- What is 35x12.50R17 in metric?What is 35x12.50R17 in metric?318/72R17 exactly, which nobody makes. The metric size everyone reaches for instead is 315/70R17, and it is 0.64 in shorter than a real 35.
- What is 31x10.50R15 in metric?What is 31x10.50R15 in metric?267/76R15 on paper, and nothing at all in practice. The closest metric size still sold on a 15-inch wheel is 235/75R15, more than two inches shorter.
- What is 37x12.50R17 in metric?What is 37x12.50R17 in metric?318/80R17 on paper, and unobtainable. Metric sizing on a 17-inch wheel runs out at 315/70R17 and 34.36 in, leaving a 2.64 inch gap with nothing in it.
- What is 285/70R17 in imperial sizing?What is 285/70R17 in imperial sizing?Exactly 32.71x11.22R17. Rounded to sizes that exist, the closest on height is a 33x12.50R17 or 33x10.50R17, and the closest on width is a 32x11.50R17.
- What is 275/60R20 in imperial sizing?What is 275/60R20 in imperial sizing?32.99x10.83R20 exactly, which rounds to 33x12.50R20 on height — within 0.01 in — while missing on width by 1.67 in, because no narrow flotation size exists on a 20.
- How tall is a 31 inch tire, really?How tall is a 31 inch tire, really?Anywhere from 30.47 to 31.61 inches. The 31 is the loosest label in truck sizing — over an inch of spread between tires sold under the same name.
- How tall is a 32 inch tire, really?How tall is a 32 inch tire, really?Between 31.91 and 32.16 inches across eight real sizes — the tightest cluster of any call size, and the one almost nobody uses in conversation.
- How tall is a 33 inch tire, really?How tall is a 33 inch tire, really?Unusually, almost exactly 33 inches. Six flotation 33s in this catalogue measure 33.00 in by definition, and the nearest metric sizes land between 32.99 and 33.06.
- How tall is a 35 inch tire, really?How tall is a 35 inch tire, really?The flotation 35s are 35.00 in exactly. The two metric sizes most often sold as 35s, 285/65R20 and 315/70R17, measure 34.59 in and 34.36 in.
- How tall is a 37 inch tire, really?How tall is a 37 inch tire, really?37.00 inches. Every one of them, with no spread at all — because there is no such thing as a metric 37, and only flotation notation reaches this size.
- How much speedometer error do 33s cause?How much speedometer error do 33s cause?Over a 265/70R17, a 33x12.50R17 makes the speedometer read 4.41% low — an indicated 70 mph is really 73.1 mph, and 100 logged miles are 104.4.
- How much speedometer error do 35s cause?How much speedometer error do 35s cause?Fitting 35x12.50R17 over 285/70R17 puts the speedometer 7.01% low. An indicated 70 mph is 74.9 mph, and every 100 miles logged is 107.0 actually driven.
- How much speedometer error do 37s cause?How much speedometer error do 37s cause?13.12% over a 285/70R17. An indicated 70 mph is 79.2 mph — a 9.2 mph gap — and 100 logged miles are 113.1 actually driven.
- Does tire size affect the odometer?Does tire size affect the odometer?Yes, by exactly the same percentage as the speedometer. Going 265/70R17 to 285/70R17, 100 displayed miles are 103.5 actual — around 350 miles a year unrecorded.
- How much does one inch of tire height change the speedometer?How much does an inch of tire height change the speedometer?Between about 3.1% and 3.9% on a truck-sized tire, depending entirely on what you started with. On a car tire near 25 inches, the same inch is worth about 4%.
- Speedometer error going from 275/55R20 to 33sSpeedometer error going from 275/55R20 to 33s3.42% — one of the smallest 33-inch swaps there is, because 275/55R20 already stands 31.91 in. An indicated 70 mph becomes 72.4 mph.
- What gear ratio for 33 inch tires?What gear ratio for 33 inch tires?From 265/70R17 on a 3.73 axle, the ratio that restores the original engine speed on 33s is 3.89:1, and 3.91:1 is sold off the shelf — two hundredths away.
- What gear ratio for 35 inch tires?What gear ratio for 35 inch tires?4.13:1 restores the original engine speed going from 265/70R17 to 35x12.50R17 on a 3.73 axle. The nearest set anyone sells is 4.10:1, which under-corrects.
- What gear ratio for 37 inch tires?What gear ratio for 37 inch tires?From 285/70R17 on a 4.10 axle, 37x12.50R17 needs 4.64:1 to restore the original engine speed. The nearest set sold is 4.70:1, which slightly over-corrects.
- What gear ratio for 40 inch tires?What gear ratio for 40 inch tires?5.01:1 from 285/70R17 on a 4.10 axle — a value that falls almost exactly midway between the two nearest sets you can buy, 4.88:1 and 5.13:1.
- Do the numbers change much going to 285/70R17?Do the numbers change much going to 285/70R17?The effective final drive drops from 3.73:1 to 3.60:1, and putting it back exactly would need a 3.86:1 axle — a ratio nobody manufactures.
- How many revolutions per mile is 285/70R17?How many revolutions per mile is 285/70R17?616.6, computed from the size code. A manufacturer's measured figure for the same size will usually be a little higher, and the reason is worth understanding.
- How many revolutions per mile is 265/70R17?How many revolutions per mile is 265/70R17?638.1. It is the stored constant most 17-inch truck speedometer questions are measured against, and the number every upgrade percentage is computed from.
- How many revolutions per mile is 33x12.50R17?How many revolutions per mile is 33x12.50R17?611.2 — and identically 611.2 for a 33x12.50R15, R16, R18 or R20. The wheel diameter has no effect on the count whatsoever.
- What does load index 100 mean?What does load index 100 mean?800 kg per tire, which converts to 1,764 lb — a nicely round metric figure sitting at the boundary between passenger and light-truck territory.
- What does load index 110 mean?What does load index 110 mean?1,060 kg, or 2,337 lb, per tire. It sits in a stretch of the table where every index point is worth exactly 30 kg, which makes nearby indexes easy to reason about.
- What does load index 116 mean?What does load index 116 mean?Index 116 is 1,250 kg per tire — a round metric figure that converts to the distinctly unround 2,756 lb, with 11,023 lb across a set of four.
- What does load index 121 mean?What does load index 121 mean?1,450 kg, or 3,197 lb, per tire. At this end of the chart it very often appears as the first half of a dual rating, such as 121/118.
- What does speed rating T mean?What does speed rating T mean?T stands for 190 km/h, or 118 mph. It sits in the tidy, evenly spaced middle of the chart and is the most common symbol on family sedans and vans.
- What does speed rating H mean?What does speed rating H mean?H means 210 km/h, or 130 mph. It is the one symbol that sits out of alphabetical order on the chart, wedged between U and V rather than between G and J.
- What does speed rating V mean?What does speed rating V mean?240 km/h, or 149 mph. It is where the chart's tidy 10 km/h steps end — the jump from H at 210 to V at 240 is three times any increment below it.
- What does speed rating R mean?What does speed rating R mean?170 km/h, or 106 mph. It is also the one speed symbol that collides with a letter already used elsewhere in the size code, which causes real confusion.
- How much taller is 285/70R17 than 265/70R17?How much taller is 285/70R17 than 265/70R17?1.10 inches taller — 32.71 in against 31.61 in — with 0.55 in of that reaching the axle, and 0.79 in of extra section width alongside it.
- Is 285/70R17 the same as 33x12.50R17?Is 285/70R17 the same as 33x12.50R17?Not the same tire, but close enough on height that a drivetrain cannot tell: 616.6 revolutions per mile against 611.2. The width is where they part company.
- Is 315/70R17 a 35 inch tire?Is 315/70R17 a 35 inch tire?It measures 34.36 in, which is 0.64 in short of a real 35 — and marginally closer to a 305/70R17 than to the 35x12.50R17 it is usually sold as.
- How much bigger is a 35 than a 33?How much bigger is a 35 than a 33?Two inches taller, exactly, and not one thousandth wider. 33x12.50R17 to 35x12.50R17 is +2.00 in of diameter, 1.00 in at the axle, and 6.06% of speedometer error.
- How much taller is 275/60R20 than 275/55R20?How much taller is 275/60R20 than 275/55R20?1.08 inches — 32.99 in against 31.91 in — and all of it sidewall. Same section width, same wheel, five points of aspect ratio between them.
- What is the sidewall height of 285/70R17?What is the sidewall height of 285/70R17?7.85 inches, or 199.5 mm — half a millimetre under a round 200. Because the sidewall is counted twice in a diameter, it is the highest-leverage figure in the code.
- What is the sidewall height of 225/45R17?What is the sidewall height of 225/45R17?3.99 inches, or 101.3 mm — within a millimetre and a half of a round four inches, and less sidewall than a much smaller 195/65R15 carries.
- How wide is a 285 tire?How wide is a 285 tire?285 mm, which is 11.22 inches. That single number is all the width tells you — the three 285s in this catalogue stand 32.71, 32.83 and 34.59 inches tall.
- How wide is a 265 tire?How wide is a 265 tire?265 mm, or 10.43 inches — but only on the rim the size was specified against. Half an inch of rim width moves the measurement by roughly two-tenths of an inch.
- How wide is a 315 tire?How wide is a 315 tire?315 mm is 12.40 inches — a tenth of an inch under the 12.50 that flotation sizing has used as its standard truck width for decades.
- What RPM at 70 mph with 35s?What RPM at 70 mph with 35s?2,315 rpm on a 4.10 axle through an 0.84 top gear — slightly more than a 33 on a 3.73 axle turns, because the deeper ratio more than offsets the taller tire.
- What RPM at 70 mph with 33s?What RPM at 70 mph with 33s?2,234 rpm on a 3.73 axle through an 0.84 top gear — 99 rpm below what the same drivetrain turned on 265/70R17.
- What RPM at 75 mph with 37s?What RPM at 75 mph with 37s?2,610 rpm on a 4.56 axle through an 0.84 top gear. At 70 mph the same combination gives 2,436 — engine speed tracks road speed exactly in proportion.