Graham FisherBy Graham Fisher

Updated November 2026

ATV tires size meaning comes down to a short string of numbers printed on the sidewall, such as 25×8-12 or 26x10R12. Once you know what each figure stands for, you can check a tire’s overall height, width and rim fit before you buy. This guide walks through how to decode those markings and avoid the most common sizing errors.

Step 1: Find the Size Code on the Sidewall

The size is molded into the sidewall, usually on the side facing out when the tire is mounted. Look for a series of numbers with a letter in the middle or at the end. Most ATV tires use one of two formats: the overall-diameter style (such as 25×8-12) or the metric-style code (such as 25x8R12). The first number is almost always the overall tire diameter in inches, not the width.

Shopping for one? See our guide: 6 Best ATV Tires by Sizes for Every Trail and Rider (2026).

Step 2: Decode Each Number in the Code

Read the code from left to right. Each part controls a different measurement:

  • First number (overall diameter): The total height of the tire from the ground to the top of the tread, in inches. A 25-inch tire measures about 25 inches tall when inflated.
  • Second number (section width): The width of the tread at its widest point, in inches. An 8 means the tire is roughly 8 inches wide.
  • The letter (construction type): An “R” means radial construction. A “-” or no letter usually means bias-ply.
  • Last number (rim diameter): The wheel diameter the tire is built to fit, in inches. A 12 means it mounts on a 12-inch rim.

Step 3: Check the Rim Diameter Before Anything Else

The rim diameter is the one measurement you cannot compromise on. A tire will not seat on a wheel of a different diameter, no matter how close the numbers look. Measure your current wheel from bead seat to bead seat across the center, or check the rim stamping on the wheel. Match that figure to the last number in the tire code.

Step 4: Compare Overall Height and Width to Your Machine

Once the rim matches, check whether the overall height and width will clear your fenders, A-arms and suspension. A larger overall diameter raises ground clearance and changes your gearing, but it can also rub at full lock or on suspension travel. Manufacturers specify the approved tire sizes for each model in the owner’s manual, and staying within those figures keeps your speedometer and drivetrain behaving as designed.

Code example Overall diameter Section width Construction Rim
25×8-12 25 in 8 in Bias-ply 12 in
26x10R12 26 in 10 in Radial 12 in
27x9R14 27 in 9 in Radial 14 in

Common Mistakes When Reading ATV Tire Sizes

  • Assuming the middle number is the tread width in millimeters. It is inches in the common ATV format.
  • Ignoring the rim diameter and buying by overall height alone.
  • Mixing bias-ply and radial tires on the same axle without checking manufacturer guidance.
  • Forgetting that a taller tire changes speedometer reading and final drive effect.
  • Choosing an oversized tire without checking fender and suspension clearance.

A basic tire pressure gauge helps you confirm that a new tire is seated and inflated to the level the manufacturer recommends. View on Amazon

A tire bead seater makes mounting and seating the tire on the rim much easier, especially for stiff sidewalls. View on Amazon

For more detail on specific brands and sizes, see ATV Tires Sizes Explained: How to Read, Match and Choose the Right Fit and 26×10 12 ATV Tires: How to Read the Size and Choose the Right Set. If you’re checking what came from the factory, Stock Honda ATV Tires: Sizes, Types and How to Choose the Right Set covers the common OEM fitments.

FAQ

Is the first number in an ATV tire size the width?

No. In the common ATV format, the first number is the overall tire diameter in inches. The second number is the section width.

What does the R mean in an ATV tire size?

The R indicates radial construction, where the internal plies run across the tire at about 90 degrees to the tread. Bias-ply tires have no R and use plies that cross at an angle.

Can I use a different rim size if the overall diameter matches?

No. The rim diameter must match the last number in the tire code, because the bead has to seat on the correct wheel. Matching overall height alone will not make a tire fit.

Conclusion

ATV tires size meaning becomes simple once you read the code in order: overall diameter, width, construction type and rim diameter. Confirm the rim first, then check overall height and width against your machine’s approved specifications. Doing those checks before you order will save you a return and a trip back to the shop.

Ready to choose one?

Graham Fisher

About Graham Fisher

Graham Fisher is part of our editorial team and reviews and edits our ATV, UTV/side-by-side & dirt bikes guides, checking product details against manufacturer specifications and owner feedback.