Tire Size to Inches Converter
Convert metric tire sizes to inches and vice versa. All dimensions in both formats.
How It Works
Metric to Inches: Enter a metric tire size (e.g. 265/70R17). The calculator divides the width by 25.4, computes sidewall height from the aspect ratio, and derives overall diameter, circumference, and all dimensions in inches.
Inches to Metric: Enter the overall diameter, section width (in inches), and rim diameter. The calculator finds the closest standard metric tire size by testing all common width/aspect-ratio combinations and selecting the one with the smallest dimensional error.
How to Read a Tire Size
A tire size like P265/70R17 breaks down as:
- P — Passenger tire (LT = Light Truck)
- 265 — Section width in millimeters
- 70 — Aspect ratio (sidewall height is 70% of width)
- R — Radial construction
- 17 — Rim diameter in inches
Flotation sizes like 33x12.50R15 use inches: 33" overall diameter × 12.5" width on a 15" rim.
Frequently Asked Questions
How do I convert a metric tire size to inches?
Divide the section width by 25.4 to get width in inches. Multiply width by the aspect ratio (as a decimal) to get sidewall height. Overall diameter = rim diameter + 2 × sidewall height. For example, a 265/70R17 is about 31.6" tall and 10.4" wide.
What is the flotation tire size format?
Flotation format lists dimensions directly in inches: diameter × width R rim-size. For example, 33x12.50R15 means 33" overall diameter, 12.5" section width, on a 15" rim. This format is common for off-road and truck tires.
Why isn't there an exact metric equivalent for every inch size?
Metric tire sizes are manufactured in standard increments (width steps of 5–10 mm, aspect ratios of 5). The calculator finds the closest standard metric size, which may differ slightly from the exact mathematical conversion.
Are metric and inch tire sizes interchangeable?
Yes, they describe the same physical tire in different units. A 285/75R16 and a 33x11.2R16 refer to nearly the same tire dimensions. The metric format is standard for highway tires while flotation format is common for off-road tires.