ATV Tire Size Calculator
Enter any flotation tire size to get diameter, circumference, revs per mile, speedometer error, and ground clearance change — instantly.
New / Upgrade Tire
Format: 27×11-12 | e.g. 25×10-12
Stock / Original Tire
Format: 25×10-12
27.00"
686 mm
11.00"
279 mm
84.82"
2.155 m
747
464 / km
Rim Diameter
12"
Sidewall Height
7.500"
190.5 mm
Revs / 100 km
46414
Rolling Radius
13.500"
342.9 mm
Check clearance & speedo
Diameter difference: +2.00" (+8.0%)
Ground Clearance & Size
Speedometer Correction
Actual Speed vs Speedometer Reading
Formula: Actual Speed = (New Diameter ÷ Stock Diameter) × Displayed Speed
25×10-12
27×11-12
AI Insight
Powered by AIGet a plain-English explanation of your results — what they mean for your vehicle and driving experience.
Quick Example
How to Use This Calculator
- 1Select Compare vs Stock mode (recommended) or Single Tire mode.
- 2Enter your new/upgrade tire in Height × Width - Rim format (e.g., 27 × 11 - 12).
- 3Enter your stock tire size in the same format (e.g., 25 × 10 - 12).
- 4Results update instantly — no button needed.
- 5Review diameter, circumference, revolutions per mile, sidewall height, and rolling radius.
- 6In Compare mode: check ground clearance gain, speedometer error %, and the side-by-side spec table.
- 7Use the actual speed table to see what your speedo will read vs your true speed at 30 / 50 / 60 mph.
Formulas Used
ATV Flotation Tire Formulas ───────────────────────────────────────────────────── Sidewall Height (in) = (Overall Diameter − Rim Diameter) ÷ 2 Circumference (in) = π × Overall Diameter Revolutions per Mile = 63,360 ÷ Circumference Revolutions per km = 39,370.1 ÷ Circumference Rolling Radius (in) = Overall Diameter ÷ 2 Comparison Formulas (vs stock) ───────────────────────────────────────────────────── Ground Clearance Change = (New Diameter − Stock Diameter) ÷ 2 Speedometer Error % = ((New Diameter − Stock Diameter) ÷ Stock Diameter) × 100 Actual Speed = (New Diameter ÷ Stock Diameter) × Displayed Speed Upsizing Safety Reference ───────────────────────────────────────────────────── 0–1" taller than stock → Safe with no mods (check clearance) 1–2" taller than stock → Check clearance at full lock & compression 2–4" taller than stock → Lift kit likely needed; check CV angles 4"+ taller than stock → Major suspension work required
Common ATV Tire Size Reference Chart
| Size | Diameter | Sidewall | Circumference | Revs/Mile | Notes |
|---|---|---|---|---|---|
| 20×7-8 | 20.00" | 6.00" | 62.83" | 1,008 | Youth ATV |
| 22×7-10 | 22.00" | 6.00" | 69.12" | 917 | Sport ATV front |
| 22×11-9 | 22.00" | 6.50" | 69.12" | 917 | Sport ATV rear |
| 25×8-12 | 25.00" | 6.50" | 78.54" | 806 | Rec ATV front stock |
| 25×10-12 | 25.00" | 6.50" | 78.54" | 806 | Rec ATV rear stock |
| 26×8-12 | 26.00" | 7.00" | 81.68" | 776 | Utility front |
| 26×10-12 | 26.00" | 7.00" | 81.68" | 776 | Utility rear |
| 27×9-12 | 27.00" | 7.50" | 84.82" | 747 | Popular trail upgrade |
| 27×11-12 | 27.00" | 7.50" | 84.82" | 747 | Popular trail upgrade |
| 28×10-14 | 28.00" | 7.00" | 87.96" | 720 | Big bore utility |
| 28×12-14 | 28.00" | 7.00" | 87.96" | 720 | Big bore utility rear |
| 30×10-14 | 30.00" | 8.00" | 94.25" | 672 | Mud / lifted build |
| 32×10-15 | 32.00" | 8.50" | 100.53" | 630 | Extreme mud / lift req. |
Circumference = π × Diameter. Revolutions per Mile = 63,360 ÷ Circumference. Sidewall = (Diameter − Rim) ÷ 2.
Want the full picture?
Read the complete ATV Tire Size Guide — covers how to read the 3-number format, terrain matching, ply ratings, the upsizing checklist, tire pressure by terrain, and a full FAQ.
Frequently Asked Questions
About This Calculator
This ATV tire size calculator is purpose-built for the flotation format used by virtually all ATV and quad tires — expressed as Height × Width - Rim Diameter (e.g., 25×10-12), where all measurements are in inches. Unlike car tire calculators that use P-Metric notation (e.g., 225/45R17), ATV tires state the overall diameter directly in the first number, making dimensional calculations straightforward.
The calculator computes seven primary metrics: overall diameter, tire width, sidewall height, rolling circumference, revolutions per mile, revolutions per kilometer, and rolling radius. In compare mode it adds four comparison metrics: ground clearance change, speedometer error percentage, odometer error percentage, and actual speed at three reference speeds (30, 50, and 60 mph displayed).
The speedometer correction formula is Actual Speed = (New Diameter ÷ Stock Diameter) × Displayed Speed. A larger tire under-reads the speedometer; a smaller tire over-reads it. Ground clearance change equals half the diameter difference because the tire sits on the ground — the axle center height rises by the amount the radius increases.
Safety ratings are based on diameter difference from stock: 0–1 inch (safe, typically no modifications), 1–2 inches (check clearance and speedometer), 2–4 inches (lift kit likely required), and 4+ inches (major suspension work required). These are general guidelines; always verify clearance on your specific ATV model at full suspension compression and full steering lock.