How to Convert Tire Size to Inches

How to Convert Tire Size to Inches

Are you in the market for new tires? Maybe you love your current ones but only have the measurements in millimeters. Or, maybe your car buddy gave you a recommendation for smaller or bigger wheels, but he didn’t provide you with the measurements in inches.

Knowing how to convert tire size to inches will make the wheel shopping process much easier. Read on for everything you need to know on how to convert tire size to inches.

Short Answer

You’ll need to determine your starting measurement. If you’re not using inches, you’re likely using millimeters or centimeters. You can follow a simple mathematical formula to get the desired measurements in inches, which we’ll explore in this guide.

Analyze Your Starting Measurement

how to convert tire size to inches

What is your starting measurement? If you measure your tires yourself and the measurements are already in inches, you’ll be set to go. But, this won’t always be the case. Maybe you obtained your measurement recommendations from a friend or an online source in a unit belonging to the metric system.

It’s essential to be able to switch your measurements to inches. You may wonder, “Why does it even matter?” The standard notation for the Society of Automotive Engineers is inches, so you mustn’t rely entirely on the metric system.

Converting from Millimeters to Inches

how to convert tire sizes

If your car tire measurements aren’t in inches, they’ll most likely be in millimeters.

You’ll normally see metric tire sizes listed in the following order: width, sidewall height (followed by an “R”), and the wheel/rim size.

First, you’ll need to convert the section width. Start with your millimeters number and divide it by 25.4. This process will yield the section width in inches. 

Once you finish converting the section width, you can move onto the sidewall height.

You can find the sidewall height by taking the section width and multiplying it by the aspect ratio ÷ 100. 

As you may have noticed, we didn’t provide the tire diameter in the description a few sentences earlier. You can get to the tire diameter by using this formula:

Diameter = double the sidewall height + the rim diameter

A Real-Life Example

It can be a bit confusing to read all this information, so we’ll offer you a specific example for clarity.

Let’s say someone provides you with the metric measurement of 225/60R16, and you’d like to convert it to inches.

You’ll find the section width by dividing 225 by 25.4, which equals 8.86 inches.

Then, you’ll find the sidewall height by performing this calculation: 8.86″ x (60 ÷ 100) = 5.316 inches.

Finally, you’ll calculate the diameter by performing this calculation: (5.136″ x 2) + 16″ = 26.632 inches.

In inches, your final truck tire size is 26.632 x 8.86 R 16.

how to convert tire sizes

Checking Your Math

It’s essential to understand the math behind what you’re doing. This way, you can get the most accurate measurements possible.

However, we’re all just people, not calculators. Maybe you didn’t ace every high school math course you took. You may make an error or two along the way, which can alter your final numbers. If you want to ensure you’re crunching your numbers correctly, you can visit this tire size conversion calculator to double-check your work.

The Importance of Converting Tire Size Correctly

how to convert tire sizes

Cars and trucks are intricate vehicles. Manufacturers built them to carry tires of specific sizes, so choosing those too large or small for your vehicle can be detrimental.

To uphold the condition of your vehicle, you need to purchase tires of the correct size. How are you supposed to do this? Simple — ensure that you are making all your size conversions correctly. 

If you buy a wheel with the wrong measurements, you run the risk of:

  • Placing extra strain on your vehicle due to excess weight
  • Decreasing your vehicle’s turning radius
  • Damaging your wheel well or suspension
  • Hydroplaning more easily on slippery surfaces
  • Creating transmission issues
  • Causing your anti-lock brakes to malfunction

When in doubt, always check your owner’s manual for the manufacturer’s suggestions on wheel size. Never exceed more than two inches of the original wheel size to protect your vehicle.

Make an Accurate Conversion for a Seamless Tire Shopping Experience!

Getting new tires is a tedious chore, but it’s inevitable — any car or truck owner will eventually need new wheels. Normal wear and tear or an unexpected nail in the road can run your tires into the ground.

Before you start shopping for new wheels, you’ll need to do some measuring and converting. Knowing your tires’ size in inches will let you make the most accurate purchase possible. Follow our guide on “how to convert tire size to inches” to ensure you get the process right the first time around!

If you find this guide helpful, feel free to check out others:

How To Measure Tire Rim Size
How To Read Trailer Tire Sizes
How Do You Measure Tire Size
How To Find Out Tire Size
How To Find Tire Diameter