Tire Size Calculator

Wheel Size
Diameter. (mm)
Tire Size
Diameter (MM)
Estimated Wheel Circumference/Computer Setting
Millimeter (MM)
Centimeter (CM)
Inches to MM Converter
An image illustrating the step-by-step process of using a Tire Calculator. The image shows a user entering the tire width, aspect ratio, and diameter values into the calculator's input fields. The next step displays the calculator automatically calculating the tire's overall diameter and circumference based on the entered values. This image visually guides the user on how to use the Tire Calculator, a helpful tool for determining tire size specifications.

Starting with a tire size calculator, you can make the right choices when replacing worn tires or configuring new vehicles. It's more than just knowing the overall diameter; there are specific dimensions that affect safety and handling.

Why Size Matters

Dialing in compatible tires and rims delivers:

✔️ Improved vehicle control

✔️ Balanced weight distribution

✔️ Maximized safety

✔️ Enhanced ride quality

✔️ Increased fuel efficiency

Key Tire Dimensions

Major tire attributes include:

  • Section Width - Tire tread contact patch width in mm
  • Aspect Ratio - Sidewall height percentage of width
  • Rim Diameter - Wheel circumference opening size
  • Overall Diameter - Total inflated height of the tire

Precisely pairing these dimensions prevents clearance issues while optimizing performance.

How Do I Find Out Tyre Size?

Here are the main ways to determine your vehicle's tire size if not clearly labeled:

  1. Check the owner's manual/glove box docs
  • The tire size is typically listed in the specs along with the recommended pressure
  1. Inspect tire sidewall
  • Etched markings display key codes: Ex. P215/65R15 where:
    • P = Passenger vehicle
    • 215 = Section width (mm)
    • 65 = Aspect ratio (%)
    • R15 = Rim diameter (inches)
  1. Refer to the door jamb sticker
  • Federal regulations mandate the display of approved tire sizes
  1. Contact vehicle manufacturer
  • Provide VIN # for exact trim specs if uncertain
  1. Measure manually
  • If damaged/illegible, width gauge and diameter tape measure

Once you locate tire dimensions, input findings into an online tire size calculator to decode specifics if still unclear. Proper sizing sets the foundation for replacement selection.

Using the Tire Calculator

Configuring tire setups involves just a few steps:

  1. Enter existing or planned rim diameter
  2. Specify the target tire section width
  3. Select the aspect ratio range
  4. View dimensional analysis

For example 16 inch wheel, 205 mm width, 40% aspect ratio tire = 25.7 inch diameter.

Terminology Lookup

Still, deciphering sizing codes on sidewalls? Referencing this decoding chart simplifies interpretation:




Radial construction


Rim diameter in inches


Aspect ratio percentage


Speed rating

Check manufacturers' manuals for specific vehicle fit guidance.

Vehicle Selection Factors

When choosing tires, also consider:

  • Wheel width - enhances cornering grip
  • Load index - supports cargo capacity
  • Speed rating - sustains high velocity
  • Tread pattern - improves traction

Component synergy optimizes mobility!

Tire Size By Vehicle

Here is a general reference chart of typical tire sizes by vehicle type:


Common Tire Sizes

Small/Compact Cars

185/65R14       195/65R15          205/55R16

Midsize Sedans

205/60R15        205/55R16         225/50R17

Large Sedans

235/55R17         245/45R18           255/45R18

Luxury Vehicles

255/45R18          255/40R19          275/40R20


225/65R17          235/60R18          265/50R20


LT245/75R16       LT265/70R17      LT285/60R20


  • First # = Tire width (mm)
  • Second # = Aspect ratio (%)
  • R + # = Rim diameter (inches)

So midsize sedans may come equipped with 205 mm width, 55% sidewall height tires on 16-inch wheels.

Always confirm specific year/make/model details for precise sizing rather than relying solely on vehicle class averages for replacement purchasing. An online tire dimension calculator can further decode tire codes as needed.

Frequently Asked Questions (FAQs)

Q1: What is tire size?

Tire size refers to the dimensions of a tire, including its width, aspect ratio, and rim diameter, which are represented by a series of numbers and letters printed on the tire sidewall.

Q2: How do I read tire size?

Tire size is typically indicated in a format such as P215/65R16. The first number represents the tire width in millimeters, the second number represents the aspect ratio (tire height as a percentage of its width), and the last number represents the rim diameter in inches.

Q3: Why is tire size important?

Tire size is important because it affects the performance, handling, and safety of a vehicle. 


Picking the right tires might not seem important, but it plays a big role in how your vehicle performs. By accurately specifying tire sizes and styles, you can improve important things like safety and how your vehicle handles.

Read More: How to Read & Determine Tire Size for Your Vehicle

                    How To Use Tire Size Calculator In Inches