Tire height calculator

Built by Nitin Raja · Last updated October 24, 2026

How tire height is calculated

Most car and SUV tires use a metric size like 265/70R17. The first number is the tread width in millimetres. The second is the aspect ratio: the sidewall is that percentage of the width. The last number is the wheel diameter in inches.

1. Sidewall: 265 mm x 70% = 185.5 mm, which is 7.3 inches.
2. Two sidewalls: the tire has one above the wheel and one below, so 7.3 x 2 = 14.6 inches.
3. Add the wheel: 14.6 + 17 = 31.6 inches. That is the tire height, also called the overall diameter.

Off-road and truck tires often use a flotation size like 33x12.50R15. Here the first number is the height itself (33 inches), then the width (12.5 inches) and the wheel size (15 inches).

Tire height comparison: what changes when you go bigger

• Speedometer: a taller tire travels further each turn, so the car moves faster than the speedometer shows. The calculator shows your real speed when the dial reads 60.
• Ground clearance: the axle rises by half of the height increase. One extra inch of tire height gives about half an inch more clearance.
• Fit: taller and wider tires can rub the wheel arches or suspension when turning. Many drivers stay within about 3% of the original height without other changes.
• Gearing and fuel use: bigger tires make the engine work a little harder and can raise fuel use.

Revolutions per mile

Revolutions per mile is how many times the tire turns in one mile: 63,360 inches divided by the tire's circumference. It matters for speedometer and odometer accuracy. Manufacturers' published figures are usually a little higher than the calculated number, because a loaded tire is slightly squashed.

Why we built this tire height calculator

Tire sizes are hard to read at a glance because one marking mixes three units. In 265/70R17 the width is in millimetres, the sidewall is a percentage of that width, and the wheel is in inches, so the height of the tire is not written anywhere. Off-road sizes such as 33x12.50R15 work the other way round and put the height first. Two sizes that look close can differ by more than an inch: 265/70R17 is 31.6 inches tall and 285/70R17 is 32.7.

When people change tire size, the height is rarely the only question. They also want to know what happens to the speedometer, how much clearance they gain and whether they are still within the 3% rule of thumb that many drivers and tire shops use. We built this page to answer all of those from the two sizes printed on the sidewalls, with the arithmetic shown so it can be checked by hand.

What this tire height calculator measures

It reads the size you type and calculates the tire's dimensions from it. Exactly what the code does:

• Metric sizes (P, LT and ST prefixes, widths 100 to 450 mm, aspect ratios 20 to 95, wheels 10 to 30 in): sidewall = width x aspect ratio / 100; overall height = wheel x 25.4 mm + 2 x sidewall.
• Flotation sizes (33x12.50R15): the first number is the height; sidewall = (height - wheel) / 2.
• Circumference = pi x height, and revolutions per mile = 63,360 inches / circumference.
• Comparison: the difference in inches, millimetres and percent; extra clearance under the axles = half the height difference; real speed when the speedometer reads 60 mph = 60 x new height / old height; and a warning above a 3% change.

The formulas were last checked on 24 October 2026. What it does not measure: the loaded height of a tire carrying a vehicle (a little less than the calculated figure), tread wear, the slightly different measured diameter each manufacturer publishes for its own tires, or whether a size actually fits your vehicle. Rubbing depends on wheel offset, suspension and steering lock, so check fitment with your tire shop.

Why this tire height calculator is different

• Both size formats, metric and flotation, in the same box.
• The full picture for a size change: height, clearance, speedometer error and the 3% check in one result, not only the diameter.
• Inches and millimetres side by side for height, width, sidewall and circumference.
• The method is shown with a worked example, and the chart of 24 common sizes is built with the same code as the calculator.
• It starts empty. No example sizes are filled in and nothing is calculated until you type your own.
• Free, no account and nothing to install. The address bar keeps your sizes, so a copied link opens with the same comparison.

Measuring something taller than a tire? Try measuring objects with your phone camera, or measure your own height.