How to Read ATV Tire Size: Every Number and Letter Explained
Last updated on October 20th, 2026 at 09:28 am
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An ATV tire size such as 25x8-12 reads as height x width - rim diameter, all in inches. That tire stands about 25 inches tall, is about 8 inches wide, and mounts on a 12-inch rim. The rim number is the only one that has to match your wheel exactly.
Some tires use a metric size such as 205/80-12 instead: width in millimeters, then sidewall height as a percent of width, then rim diameter in inches. Below you will find that math worked out, real stock sizes and pressures from owner’s manuals, and a calculator that compares your stock size with a new one.
What each number in 25x8-12 means
25 is the overall height of the tire, measured when it is mounted and inflated to the recommended pressure, per ATV.com. It sets ground clearance, gearing and speedometer error.
8 is the tire width in inches. One older manual page describes this number as the recommended rim width, but ATV.com and the tire makers’ listings treat it as the tire’s width. Rim width is not part of the size code, so check your manual or the tire maker’s fitment chart for it.
12 is the rim diameter in inches, measured across the wheel where the tire bead sits. Written as 25x8-12, 25x8x12 or 25x8.00-12, it means the same thing, and manuals often put “AT” in front, as Yamaha does with AT25 x 10-12.
Metric ATV tire sizes (205/80-12)
Metric sizes are less common on ATVs but turn up on some tires. Here is 205/80-12 worked out.
| Part (205/80-12) | Meaning | Math |
|---|---|---|
| 205 | Section width in millimeters | 205 mm / 25.4 = 8.1 in |
| 80 | Aspect ratio: sidewall height as a percent of width | 80% of 205 mm = 164 mm = 6.5 in |
| R or - | R means radial; a dash usually means bias-ply (as ATV.com notes, no letter means bias) | |
| 12 | Rim diameter in inches | Height = 12 + 2 x 6.5 = 24.9 in |
So a 205/80-12 is roughly a 25-inch-tall, 8-inch-wide tire on a 12-inch rim, very close to a 25x8-12. The formula for any metric size is rim + 2 x (width x aspect % / 25.4).
Be careful with sites that put the 205 “after the letter.” It always comes first, before the slash.
Stock ATV tire sizes and pressures from owner’s manuals
Front and rear sizes differ on most ATVs, and so do pressures. The Polaris Sportsman 570 runs 25x8-12 up front and 25x10-12 in the back, while its EPS Premium trim steps up to 26x8-14 and 26x10-14.
Pressure is far lower than a car tire, and it varies by maker. Read the number off your own machine, not the one molded on the tire.
| Machine (manual) | Front size | Rear size | Cold pressure |
|---|---|---|---|
| Polaris Sportsman 570 / 570 EPS (2025 manual) | 25x8-12 | 25x10-12 | 7.0 psi front and rear |
| Polaris Sportsman 570 EPS Premium (2025 manual) | 26x8-14 | 26x10-14 | 7.0 psi front and rear |
| Yamaha Grizzly 700 FI (owner’s manual) | Not shown on the page checked | AT25 x 10-12 (Dunlop KT425, tubeless) | 5.0 psi front, 4.3 psi rear (minimum 4.6 / 3.9) |
| Honda TRX420TM Rancher (owner’s manual) | Not shown on the page checked | Not shown on the page checked | 3.6 psi front and rear |
Yamaha’s manual also warns that pressure below the minimum can let the tire come off the rim in hard riding, and that bead seating should never exceed 36 psi. It says higher pressure and fast inflation can burst a tire, so inflate slowly.
Honda tells owners to use only the size and type the manual specifies and to inflate with a hand pump, not a service-station air hose.
How to find your ATV’s correct tire size
- Read the tire label or specifications page for your exact model and year (front and rear can differ).
- Match the size molded on the tire sidewall against that list.
- Keep the rim diameter unchanged unless you are buying wheels too.
- Check wheel bolt pattern and width in the tire maker’s fitment chart before ordering.
- Replace tires in axle pairs at minimum, and keep fronts matched to fronts and rears to rears.
Polaris’s manual says to always use the original equipment size and type when replacing tires. For pressure checks, a low-range gauge reads accurately where a truck gauge does not: try an 0-15 psi tire gauge or a hand tire pump.
ATV tire size swap calculator
Type your stock size and the size you are considering. The calculator decodes both, checks the rim, and shows how far your real speed will drift from the speedometer.
Examples: 25x8-12, 25x8x12, 25x8.00-12, AT25x10-12, 205/80-12. Estimates come from the size code only.
The result is arithmetic on the size code: diameter ratio for speed, inverse ratio for engine rpm. Printed sizes are nominal, so a real tire can measure slightly different.
Use it with the manual, not instead of it. For cars and trucks, our tire size calculator does the same job, and the full calculator list covers gearing and winch loads.
What a taller tire does to speed and gearing
Because the gearing stays the same, a taller tire covers more ground per engine revolution. That feels like a taller final drive: slower acceleration, more load on the clutch and belt, and a speedometer that under-reads.
The table assumes a 25-inch stock tire and a speedometer reading 30 mph. It is calculated from the diameter ratio.
| New height (stock 25 in) | Diameter change | Real speed at 30 mph indicated | Engine rpm at same speed |
|---|---|---|---|
| 26 in | +4% | 31.2 mph | -3.8% |
| 27 in | +8% | 32.4 mph | -7.4% |
| 28 in | +12% | 33.6 mph | -10.7% |
| 29 in | +16% | 34.8 mph | -13.8% |
| 30 in | +20% | 36.0 mph | -16.7% |
Wider tires add traction and steering effort without changing speed. Narrower tires do the opposite. If a symptom like bogging or belt slip shows up after a swap, see our ATV and UTV troubleshooting guide.
Prices by tire type and size are in our off-road tire cost guide.
Other sidewall markings, wear limits and safety
- Ply rating (4-ply, 6-ply): a strength rating. Higher numbers resist punctures better but ride stiffer.
- Direction arrows and F/R labels: many ATV tires are position-specific and have a rotation arrow, so mount them facing the right way.
- Wear limit: Polaris says to replace tires at 3 mm (⅛ in) of tread or less. Honda says to replace before center tread reaches 3/16 in (4 mm), and to replace any tire with a bump, bulge or visible cord (Honda manual p. 146, p. 145).
- Public roads: the Polaris warning label says never use the ATV on public roads, whatever tires it wears.
- Load and speed ratings: not always printed on ATV tires, so rely on the manual’s load limits.
For the same math on car-style sizes, see how to read mud tire sizes, and for load numbers on truck tires the tire load index chart.
ATV tire types by terrain
The tread pattern matters as much as the size. Pick the type for where you ride, then the size your manual allows.
Stay at your manual’s pressure whichever tread you choose. Truck-style air-down numbers do not apply here; for trucks and Jeeps, use our off-road tire pressure calculator.
| Type | Best for | Notes |
|---|---|---|
| All-purpose / trail | Mixed riding, work, trails | Closely spaced lugs give a larger contact patch and long wear; the most common stock choice |
| Mud | Deep mud and snow | Deeper, wider-spaced lugs that clear mud; wear faster and ride rougher on hard ground |
| Sand / paddle | Dunes | Paddle-style rears and ribbed fronts; not useful elsewhere |
| Motocross / track | Loose dirt tracks | Stiff lugs for cornering and acceleration |
| Snow / winter | Ice and snow | Some can be studded; check local rules |
FAQs
In 25x8-12, 25 is the overall tire height in inches, 8 is the width in inches, and 12 is the rim diameter in inches.
In 205/80-12, 205 is the width in millimeters, 80 is the aspect ratio (sidewall height as a percent of width) and 12 is the rim diameter in inches. Height is 12 + 2 x 6.5 = about 24.9 inches.
Only the last number, the rim diameter. Width must also fit the rim width the tire maker lists for that tire.
On the Polaris Sportsman 570 the stock fronts are 25x8-12 and the rears 25x10-12. The wider rears add traction and stability while narrower fronts keep steering lighter.
ATV.com says a stock machine can typically handle one, maybe two, sizes larger, but taller tires strain the drivetrain, brakes and suspension. Check your manual, and note that Polaris tells owners to use the original size and type.
Check the tire information in your owner’s manual or the label on the machine, then compare it with the size molded on the tire.
Related guides
- How to Read Mud Tire Sizes: A Simple Guide to Every Number Shown
- Most Reliable 4x4 ATV: What Recall Records and Specs Show
I'm Suryashankar Dasgupta, the founder of Off-Road Handbook. I've been off-roading for years in the USA, including California and Texas, and have ridden mountain and desert terrain abroad. I've also driven a Jeep Compass for more than seven years, so I know the day-to-day side of Jeep ownership first-hand, from the Uconnect screen to the warning lights. Every guide here is researched from manufacturer owner's manuals, NHTSA recall and service-bulletin records and other trusted sources, checked against them before it is published, and corrected when we find a mistake. You can read how we work in our editorial policy: https://offroadhandbook.com/editorial-policy/
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