Farm tires come in both metric and imperial sizes, and knowing how to convert between them is key to selecting the right replacement. Whether you’re outfitting a tractor, sprayer, or harvester, using the correct tire size prevents mismatched rolling diameters, traction issues, and driveline wear. This farm tire conversion chart makes it easy to match metric tires to their imperial (inch-based) equivalents.
Why You Need a Farm Tire Conversion Chart
Farm equipment manufacturers and tire brands often use different sizing systems. A 420/85R30 metric tire is functionally the same as a 16.9R30 imperial tire. If you don’t convert correctly, you risk installing incompatible tires that affect ground speed, torque, and fuel use.
Before finalizing your selection, confirm tire ratios using the
4×4 Tractor Tire Ratio Calculator or
4WD Wheel Ratio Calculator.
Farm Tire Metric to Imperial Conversion Chart
Use this chart to convert common farm tire sizes from metric to imperial format. This helps ensure compatibility with your rims and maintains proper rolling circumference for 2WD, MFWD, and 4WD systems.
| Metric Size | Imperial Equivalent | Rim Diameter | Common Use |
|---|---|---|---|
| 240/85R24 | 9.5R24 | 24″ | MFWD Front, Compact Tractors |
| 280/85R24 | 11.2R24 | 24″ | Compact Rear |
| 320/85R28 | 12.4R28 | 28″ | Utility Rear |
| 340/85R28 | 13.6R28 | 28″ | General Field Rear |
| 380/85R28 | 14.9R28 | 28″ | Field Tractor Rear |
| 420/85R30 | 16.9R30 | 30″ | Row Crop Rear |
| 460/85R34 | 18.4R34 | 34″ | Rear Tire for High HP Tractors |
| 520/85R38 | 20.8R38 | 38″ | Heavy-Duty Field Tractors |
How to Read Farm Tire Sizes
Metric Format Example: 420/85R30
- 420 = Width in millimeters
- 85 = Aspect ratio (sidewall height is 85% of width)
- R = Radial construction
- 30 = Rim diameter in inches
Imperial Format Example: 16.9-30 or 16.9R30
- 16.9 = Width in inches
- – or R = Bias or radial construction
- 30 = Rim diameter in inches
If you’re ever unsure, simply plug the size into the
Tractor Tire Ratio Calculator to see compatible matches.
Tips for Using Converted Farm Tire Sizes
- Always verify rolling circumference, not just size label
- Keep tire types (bias or radial) consistent per axle
- Match front and rear ratios precisely on 4WD tractors
- Double-check rim width compatibility before purchase
If you’re changing to a taller or wider tire, make sure your tractor is balanced correctly using the
Ballast Calculator for Tractor Tires.
Conversion and Transport Considerations
Converting to larger tires increases your tractor’s height and weight. This impacts trailer loading angles and clearance under barns or equipment sheds.
Use the Garden Tractor Ramp Calculator to safely load your equipment onto a trailer with the correct ramp length and angle.
Conclusion
Farm tire conversion doesn’t have to be complicated. With this chart, you can confidently switch between metric and imperial tire labels while ensuring proper size, fit, and performance. It’s the easiest way to avoid mismatched tires, protect your equipment, and keep your operation running smoothly.
For the best results, pair this chart with these essential tools:
- 4×4 Tire Ratio Calculator
- 4WD Wheel Ratio Calculator
- Ballast Calculator
- Ramp Angle Calculator
- Hourly Rate Calculator
Use this chart to pick the right tire, avoid guesswork, and get more out of every acre.