Tire Specifications
Select width, aspect ratio & rim size from dropdownsWidth
Select
Aspect %
Select
Rim (in)
Select
Select all three values
Smaller Tire Optional
Width
Select
Aspect %
Select
Rim (in)
Select
Current Tire Required
Width
Select
Aspect %
Select
Rim (in)
Select
Bigger Tire Optional
Width
Select
Aspect %
Select
Rim (in)
Select
Select the Current tire (required)
Calculated Specifications
Adjacent Sizes (Same Rim)
One size smaller and one size bigger than your selection, matched by overall diameter on the same rim.
Sidewall Cross Section
Revolutions Comparison
Comparison Results
Specification Comparison
Tire Size Chart
| Tire Size | Overall Dia. | Width | Sidewall | Circumference | Revs/Mile | Revs/Km | Compare |
|---|---|---|---|---|---|---|---|
| Scroll down to load the tire size chart… | |||||||
For reference only. Always verify fitment with a professional before purchasing tires.
Need to compare two tire sizes? Try our Tire Size Comparison for accurate results.
How to Read a Tire Size
A tire size such as 265/70R17 looks like a code, but each part tells you something useful. The first number is the tire’s section width in millimeters, measured sidewall to sidewall. The second number is the aspect ratio — the sidewall height shown as a percentage of that width, so a lower number means a shorter, sportier sidewall. The letter R simply confirms the tire uses radial construction, which is standard on almost every tire sold today. The final number is the rim diameter in inches, and it must match your wheel exactly — this is the one measurement that has zero room for rounding. Once you know these four values, you can calculate the tire’s actual sidewall height, overall diameter, and circumference, which is exactly what the breakdown below does for you.
265
Section Width
Width in mm, sidewall to sidewall. 265 mm ≈ 10.4″
70
Aspect Ratio
Sidewall height as % of width. Lower = sportier.
R
Radial
Plies run radially at 90°. Standard on all modern tires.
17
Rim Diameter
Wheel size in inches. Must match exactly.
Sidewall = 185.5 mm
265 mm
×
70%
=
185.5 mm (7.3″)
Diameter = 752.1 mm (29.6″)
(185.5 × 2 ÷ 25.4)
+
17
=
29.6 inches
Circumference = 2362.4 mm (93.0″)
29.6″
×
π
=
93.0 inches
Looking for your tire size? Browse our Tire Size Chart.
Frequently Asked Questions
Common questions about tire sizes and specificationsHow do I convert a metric tire size to inches?
To convert a metric tire size to inches, multiply the section width by the aspect ratio and divide by 100 to find the sidewall height in millimeters. Double that number, convert it to inches by dividing by 25.4, then add the wheel diameter. For example, on a 265/70R17 tire: sidewall height = 265 × 0.70 = 185.5mm. Overall diameter = (185.5 × 2 ÷ 25.4) + 17 = approximately 29.6 inches. A tire size converter automates this calculation instantly.
What do the numbers in a tire size mean (e.g. 265/70R17)?
In a tire size like 265/70R17, “265” is the section width in millimeters, “70” is the aspect ratio (sidewall height as a percentage of width), “R” indicates radial construction, and “17” is the wheel rim diameter in inches. Reading these three numbers correctly is the first step to accurately converting or comparing tire sizes.
What is the aspect ratio on a tire?
The aspect ratio is the second number in a tire size, such as “70” in 265/70R17. It represents the sidewall height as a percentage of the tire’s section width. A ratio of 70 means the sidewall is 70% as tall as the tire is wide. Lower aspect ratios, typically 35 to 45, create a sportier, low-profile look, while higher ratios, typically 65 to 80, provide a taller sidewall and a softer ride.
Can I change my tire size without affecting my speedometer?
You can only avoid speedometer error if the replacement tire has the exact same overall diameter as the original. A larger-diameter tire makes the speedometer read slower than your actual speed, while a smaller tire makes it read faster than your actual speed. A tire size comparison tool can calculate the exact speedometer error at any given speed before you buy new tires.
What does the “R” mean in a tire size?
The “R” in a tire size stands for Radial, meaning the internal fabric plies run radially across the tire at a 90-degree angle to the direction of travel. Nearly all modern passenger, SUV, and light-truck tires use radial construction. Older bias-ply tires used the letter “D” instead but are rarely sold today.
How much of a tire size difference is safe or acceptable?
Most tire professionals and manufacturers recommend keeping any replacement tire within plus or minus 3% of the original tire’s overall diameter. Exceeding that range can cause fender or suspension clearance problems, throw off ABS and traction-control calibration, distort speedometer and odometer readings, and in some cases void a vehicle’s warranty.
How do I convert a flotation size like 33×12.5R17 to a metric tire size?
Flotation sizes, common on trucks and SUVs, are expressed entirely in inches: the first number is overall diameter, the second is section width, and the number after “R” is rim diameter. To convert 33×12.5R17 to metric, calculate the width as 12.5 × 25.4 which rounds to about 315mm, and the sidewall height as (33-17)/2 × 25.4 which is about 203mm. Dividing sidewall by width gives an aspect ratio near 64%, making 33×12.5R17 roughly equivalent to 315/64R17.
Why do revolutions per mile matter when comparing tire sizes?
Revolutions per mile (or per kilometer) tell you how many times a tire rotates to cover that distance, which is directly tied to overall tire diameter. A taller tire has a larger circumference and therefore turns fewer times per mile, while a shorter tire turns more times per mile. Since your vehicle’s speedometer and odometer are calibrated to the original tire’s revolutions per mile, a significant change in this number is what causes reading errors after a tire size change.
Will a plus-size or oversized tire fit my vehicle?
Whether a larger “plus-size” tire fits depends on available clearance in the wheel well, suspension travel, and the offset of the wheel itself, not just the tire’s calculated diameter. Even when a tire size calculator shows the new size is within a safe percentage difference, it’s still important to check your vehicle’s specific fitment guide or consult a tire shop, since body kits, lift kits, and lowering springs can change the clearance available.
How accurate is an online tire size converter or calculator?
An online tire size converter is highly accurate for the mathematical conversion itself, since it applies the same standard formulas tire manufacturers use to calculate sidewall height, overall diameter, circumference, and revolutions per mile. The results are theoretical dimensions based on the size code; actual measured tire dimensions can vary slightly, by roughly 1 to 2%, between brands and models due to differences in construction and tread design.