Inches to Metric Tire Size Converter

Enter target inch dimensions to search common 5 mm width and 5-point aspect-ratio steps for a close theoretical metric size.

Target diameter (in)

Target width (in)

Wheel diameter (in)

—Nearby metric size

—Calculated diameter

—Calculated width

—Diameter difference

—Searches common 5 mm section-width and 5-point aspect-ratio increments. It is a size-math suggestion only, not a vehicle fitment recommendation.

Automotive tolerance cluster

Calculate the nominal spec, then expose how real-world input spread can move it

Vehicle calculations are often exact only on paper. This cluster keeps the base result while making rolling radius, gearing, wheel measurements and performance-input sensitivity visible.

Tire size Gear ratio Speedometer

All 23 automotive tools

RPM ↔ SpeedRolling diameter + ratio spread → calibration envelope Engine DisplacementBore/stroke spread → swept-volume envelope Wheel BackspacingWidth/flange/input spread → backspacing envelope Wheel OffsetWidth/offset spread → inner/poke envelope Power-to-WeightPower/mass spread → ratio sensitivity Speed Per GearTire/gearing/redline spread → per-gear envelope Tire ComparisonReal rolling diameter → speedometer envelope Tire SidewallWidth/aspect spread → sidewall/diameter envelope