Need to convert metric tractor tire sizes to imperial formats? Many farmers and equipment owners run into this issue when replacing or upgrading tires. Manufacturers often use different sizing systems, but this metric conversion chart helps you find the right imperial match quickly. Use it to avoid size mismatches that can affect traction, rolling circumference, and 4WD synchronization.
Why Convert Tractor Tire Metric Sizes?
Metric and imperial tire sizes can describe the same actual tire—but in different units. If you’re not familiar with both formats, it’s easy to choose a size that doesn’t fit your rims or throws off your 4WD gear ratio. Using the wrong size may also impact your fuel economy and increase tire wear.
Before buying, always verify compatibility with a
4×4 Tractor Tire Ratio Calculator or
4WD Wheel Ratio Calculator.
Tractor Tire Metric to Imperial Conversion Chart
This chart helps you convert popular metric tractor tire sizes into their imperial (inch-based) equivalents. It includes the closest matching width and rim diameter, based on average rolling circumference.
| Metric Size | Imperial Equivalent | Rim Diameter (inches) | Common Use |
|---|---|---|---|
| 240/85R24 | 9.5R24 | 24″ | MFWD Front, Compact |
| 280/85R24 | 11.2R24 | 24″ | Compact Rear |
| 320/85R28 | 12.4R28 | 28″ | Utility Rear |
| 340/85R28 | 13.6R28 | 28″ | Utility Rear |
| 380/85R28 | 14.9R28 | 28″ | Field Tractor Rear |
| 420/85R30 | 16.9R30 | 30″ | Field Tractor Rear |
| 460/85R34 | 18.4R34 | 34″ | Row Crop Rear |
| 520/85R38 | 20.8R38 | 38″ | High HP Rear |
How to Convert Metric Tire Sizes to Inches
Use this formula to estimate the height (diameter) of a metric tire in inches:
Tire Diameter = ((Section Width × Aspect Ratio × 2) ÷ 25.4) + Rim Diameter
Example: 420/85R30
- 420 × 0.85 × 2 ÷ 25.4 = 28.13″
- 28.13″ + 30″ = 58.13″ total height
Instead of calculating manually, you can get exact results using the
Tractor Tire Ratio Calculator.
Match Front and Rear Tire Ratios Correctly
Incorrect tire conversions on a 4WD tractor can lead to gear binding and damage. Make sure your front tires rotate slightly faster than the rear tires—usually a 1–5% lead.
Verify ratios with the 4WD Tractor Wheel Ratio Calculator before mounting any new tire set.
Don’t Forget About Ballasting
Switching to a wider or taller tire? You may need more ballast. Tire size changes affect your tractor’s weight distribution, especially on slopes or when towing implements.
Use the Ballast Calculator for Tractor Tires to find out how much weight to add for optimal performance and safety.
New Tire Size? Check Ramp Angles for Transport
Larger tires raise the overall height of your tractor. If you haul your equipment, use the Garden Tractor Ramp Calculator to get the right ramp angle and avoid loading accidents.
Conclusion
Whether you’re buying replacements, upgrading for field conditions, or mixing front and rear sets, converting tractor tire sizes from metric to imperial is a must. Use this chart to guide your purchase and confirm compatibility with the help of trusted calculators.
Use these free tools to work smarter:
- 4×4 Tire Ratio Calculator
- 4WD Wheel Ratio Calculator
- Ballast Weight Calculator
- Ramp Angle Calculator
- Hourly Rate Calculator
Use this conversion chart to find the right size every time—and keep your tractor operating at peak performance.