Tyre Size Calculator

Use our tyre size calculator to compare and calculate tyre sizes. Enter your current and new tyre dimensions to see the difference instantly!

Current Tyre

New Tyre

Section Width:265 mm (10.43 in)Aspect Ratio:70%Sidewall Height:185.50 mm (7.30 in)Wheel Diameter:17 inTotal Diameter:31.61 inCircumference:99.3 inRevs per Mile:638

How to Read 265/70R17 Tyre Size? What Does 265/70R17 Mean?

Let's break down the tyre size 265/70R17 to understand what each number and letter means:

265 (Section Width)

The first number "265" represents the tyre's width in millimeters, measured from sidewall to sidewall. In this case, the tyre is 265 millimeters wide (approximately 10.43 inches).

70 (Aspect Ratio)

The number "70" after the forward slash is the aspect ratio or profile. This means the tyre's sidewall height is 70% of its width. For a 265mm wide tyre, the sidewall height would be185.50mm (approximately 7.30 inches).

R (Construction)

The letter "R" indicates this is a Radial tyre, which is the most common type of tyre construction today. Radial tyres have layers of cord that run radially (at 90 degrees) from the center of the tyre.

17 (Wheel Diameter)

The last number "17" specifies the wheel diameter in inches. This means the tyre is designed to fit a 17-inch wheel. The total diameter of the tyre would be the wheel size plus twice the sidewall height.

Additional Measurements

Using these numbers, we can calculate other important measurements:

  • Total Tyre Diameter: 17 inches (wheel) + 2 × 7.30 inches (sidewall height) = 31.61 inches
  • Sidewall Height: 185.50mm or 7.30 inches (on each side)
  • Circumference: Approximately 99.3 inches (based on π × total diameter)
  • Revolutions per Mile: About 638 (varies slightly based on load and air pressure)

Popular Tyre Size Comparisons

205/55R16vs215/55R16
225/60R17vs235/60R17
245/65R17vs265/70R17
195/65R15vs205/65R15
225/45R18vs235/45R18
215/55R17vs225/55R17

Frequently Asked Questions

What is a tyre size calculator?

A tyre size calculator is a tool that helps you understand and convert tyre measurements. It can calculate dimensions like overall diameter, sidewall height, and circumference based on tyre size specifications (e.g., 265/70R17).

How do I read tyre sizes?

Tyre sizes (e.g., 265/70R17) consist of three main numbers: the width in millimetres (265), the aspect ratio (70, representing sidewall height as a percentage of width), and the wheel diameter in inches (17). The 'R' indicates radial construction.

Why is tyre size important?

Correct tyre sizing is crucial for vehicle performance, safety, and accuracy of your speedometer. It affects handling, fuel efficiency, and ensures proper fitment without rubbing against vehicle components.

Can I use different tyre sizes on my vehicle?

While some variation is possible, it's important to stay within manufacturer-recommended sizes. Significant changes can affect vehicle handling, speedometer accuracy, and clearance. Use our calculator to compare different sizes and their effects.

What is aspect ratio in tyre sizing?

Aspect ratio is the tyre's sidewall height as a percentage of its width. For example, in a 265/70R17 tyre, 70 means the sidewall height is 70% of the 265mm width. A lower aspect ratio means a shorter sidewall.

How does tyre size affect performance?

Tyre size impacts various aspects of performance including handling, acceleration, braking distance, and fuel economy. Larger tyres may improve stability but can reduce acceleration, while smaller tyres might improve fuel efficiency but could affect ride comfort.

What happens if I install the wrong tyre size?

Installing incorrect tyre sizes can lead to several issues: inaccurate speedometer readings, altered vehicle handling, reduced fuel efficiency, potential rubbing against vehicle components, and possible damage to your vehicle's drivetrain. It may also affect your vehicle's ABS and traction control systems.

How do I calculate tyre circumference?

Tyre circumference can be calculated by multiplying the total diameter (wheel diameter + twice the sidewall height) by π (3.14159). Our calculator automatically performs this calculation for you, giving you accurate results for any tyre size.

What's the difference between P-metric and LT tyres?

P-metric tyres are designed for passenger vehicles, while LT (Light Truck) tyres are built for heavier vehicles and loads. LT tyres typically have stronger sidewalls and higher load ratings. The sizing format is similar, but load capacities and recommended pressures differ.

How do plus-size tyre upgrades work?

Plus-sizing involves increasing wheel diameter while decreasing sidewall height to maintain a similar overall tyre diameter. For example, going from 215/65R16 to 215/55R17. This can improve handling but may affect ride comfort and cost more.

Why do my tyre sizes have different measurements in inches and millimetres?

Tyre sizing uses a mix of metric and imperial measurements due to historical industry standards. Width is in millimetres (e.g., 265mm), while wheel diameter is in inches (e.g., 17 inches). Our calculator helps convert between these measurements for easier comparison.

How often should I check my tyre size?

You should verify your tyre size when: replacing tyres, buying new wheels, experiencing unusual handling, noticing uneven wear, or considering performance modifications. Always ensure replacements match your vehicle's specifications or are properly calculated alternatives.

What does 225 65r17 mean?

“225” indicates the tyre is 225mm wide; “65” tells us the height of the tyre's sidewall the tyre is 65% of its width—or 146.25mm; and “17” lets us know it will fit 17-inch wheel rims.

What is 225 in tyre size?

Section width of tyre (Example: 225/45R17) The section width can be converted to inches by dividing the width in millimetres by 25.4 like so: (225 millimetres) / (25.4 mm/in) = 8.86 inches.

What do the numbers 265-70R17 mean?

265 is the width, 70 is the aspect ratio, R stands for radial, 17 is the wheel diameter and 115T is the load index and speed symbol.

Which tyre size is best for a car?

You can switch to larger car tyres but experts recommend upgrading within 3% of the original diameter of your car tyres. Switching to unnecessarily large tyres will not only affect your car's mileage but may also impact handling and ride quality.

What Our Users Say

Michael Chen

Porsche 911

The tyre size calculator is incredibly precise! Helped me find the perfect fit for my sports car.

2023-12-18

Sofia Rodriguez

BMW X5

The metric to imperial conversion feature is fantastic. Makes comparing tyre sizes so much easier.

2023-12-09

Tom Anderson

Ford F-150 Raptor

Great for understanding how different tyre sizes affect ground clearance.

2023-11-30

Rachel Kim

Volkswagen GTI

This tool is essential for anyone looking to modify their vehicle's stance.

2023-11-21

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Mazda CX-5

Accurate, fast, and mobile-friendly. It's my go-to tool before every road trip.

2023-11-15

Priya Sharma

Toyota Corolla

Great for both metric and imperial users. The explanations are very beginner-friendly.

2023-11-08

Ahmed Al-Farsi

Nissan Patrol

Very useful for comparing off-road vs. highway tyres. Interface is smooth.

2023-11-01

Emma Thompson

Audi Q7

Love how easy it is to calculate different tyre sizes. Made my winter tyre selection a breeze!

2023-12-15

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Tesla Model 3

Perfect tool for calculating speedometer accuracy with different tyre sizes.

2023-12-06

Sarah Johnson

Mercedes-AMG C63

The calculator helped me maintain my car's performance while upgrading tyres.

2023-11-27

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Honda Civic

Swapping to larger tyres was stress-free thanks to this calculator. Highly recommend for any DIYer.

2023-11-19

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Hyundai Elantra

The best resource for learning about tyre specs and what fits my car.

2023-11-12

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Peugeot 208

The only calculator that actually matches my local tyre shop's measurements.

2023-11-06

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Mini Cooper S

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2023-10-29

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Toyota 4Runner

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2023-12-12

Laura Miller

Range Rover Sport

Used this to upgrade my SUV's tyres. The calculations were spot on!

2023-12-03

Alex Martinez

Subaru WRX STI

Excellent for comparing different tyre options. Very user-friendly interface!

2023-11-24

Emily Brown

Tyre Shop Owner

I love the clear comparison charts. Helped me explain tyre changes to my customers.

2023-11-17

Chris Green

Chevrolet Camaro

I used this to check fitment for custom wheels. Saved me from a costly mistake!

2023-11-10

Helen Scott

Volvo XC60

Quickly found the correct size when switching from summer to all-season tyres.

2023-11-03