Metric / Inch Tire Size Converter

Enter your tire size information into one side of the tire size converter below to convert metric tire sizes to inches or inch tire sizes to their metric equivalents.

Metric Tire Size

/ R
(Example: 315 / 75 R 16)

Inch Tire Size

x -
(Example: 35 x 12.50 - 16)

( Full Calculator: Metric To Inch Tire Size Converter )

Ring and Pinion Gear Calculator

Enter your original tire size and gear ratio into the form below along with your new tire size to find your recommended ring and pinion gear ratio.

OEM Tire Diameter:
OEM Gear Ratio:
New Tire Diameter:
New Gear Ratio:

( Full Calculator: Ring and Pinon Gear Calculator )

Gear Ratio Calculator

Enter the number of teeth found on your ring gear as well as your pinion gear in the boxes below to calculate their combined ring and pinion gear ratio.

Ring Gear Teeth:
Pinion Gear Teeth:
Gear Ratio:

( Full Calculator: Gear Ratio Calculator )

Crawl Ratio Calculator

Enter your transmission, transfer case, and axle gear ratios into the left side of the form below and press the calculate button to find your final crawl ratio.

Transmission Ratio: : 1
Transfer Case Ratio: : 1
Axle Gear Ratio: : 1
Final Crawl Ratio:
: 1

( Full Calculator: Drivetrain Crawl Ratio Calculator )

MPH Offset / Corrected MPH

Enter your original and new tire sizes into the table below and select a base speed to calculate your speedometer's offset and your vehicles actual speed.

New Tire Diameter:
OEM Tire Diameter:
Speedometer (MPH):

Actual Speed: MPH
Speed Offset: %

( Full Calculator: Vehicle Speed Offset Calculator )

Engine RPM Calculator

Enter your axle gear ratio, tire diameter, vehicle speed, and transmission gear ratio in the blue fields and click the calculate button to find your engine RPM.

Axle Gear Ratio: : 1
Tire Diameter: Inches
Vehicle Speed: MPH
Transmission Ratio: : 1

Engine Speed: RPM

( Full Calculator: Engine RPM Calculator )

Wheel Calculators

Backspacing and Offset Conversion
Metric and Inch Bolt Pattern Conversion
Wheel Bolt Pattern Calculator
Wheel Measurement Guide

Shock and Coilover Calculators

Coilover Spring Rate Calculator
Shock Oil Volume Calculator

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Street Legal Laws

To find the street legal laws for your state including maximum suspension lift heights and tire size rules visit