Tire Size to Inches Converter
Metric tire sizes hide their real dimensions. Enter one and see every measurement in inches and millimetres side by side.
Metric notation in, inches out.
265/70R17 in inches — also written 31.6x10.4R17 (flotation style)
Overall diameter
31.61"
802.8 mm
Section width
10.43"
265 mm
Sidewall height
7.3"
185.5 mm
Wheel diameter
17"
431.8 mm
Circumference
99.3"
2522.07 mm
Revs / mile
638.1
rotations
Revs / km
396.5
rotations
Aspect ratio
70
% of width
Why metric sizes are hard to picture
A size like 265/70R17 tells you the wheel is 17 inches, but
gives no direct clue how tall the whole tire is — the part that
matters for clearance and gearing. You have to derive it: 70% of 265mm is
a 185.5mm sidewall, which is 7.3 inches, doubled and added to the 17-inch
wheel for a 31.6-inch overall diameter. This tool runs that chain for you
and also gives the flotation-style "31x10.5R17" equivalent that off-road
and truck shoppers use.
Comparing two sizes rather than converting one? The comparison calculator
shows the differences and speedometer impact directly.
Frequently asked questions
- How do I convert a metric tire size to inches?
- Divide the section width (mm) by 25.4 to get width in inches. For height, multiply the width by the aspect ratio percentage to get sidewall in mm, divide by 25.4 for inches, then add it twice to the wheel diameter for overall diameter. For 265/70R17: sidewall is 265 × 0.70 = 185.5mm = 7.3", so diameter is 17 + 2(7.3) = 31.6". This calculator does it instantly.
- What is the flotation (inch) tire size equivalent?
- Light-truck flotation sizes are written diameter × width R wheel, e.g. 31x10.5R15. The converter shows the flotation-style equivalent of any metric size so you can cross-shop between the two systems.
- What does "revolutions per mile" tell me?
- It is how many times the tire rotates to cover a mile, which is what your speedometer and odometer actually count. A smaller number means a taller tire. Two tires with different revs per mile will give different speedometer readings on the same vehicle.