Metric to Inch Tire Size Converter Convert between 225/65R17 and 33x12.5R15 formats
Pro Metric/Inch Converter
Comprehensive conversion with equivalent sizes across rim diameters and popular off-road conversions
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Equivalent Sizes Across Rim Diameters
These sizes maintain approximately the same overall diameter (802.8mm) on different rim sizes:
| Rim | Metric Size | Inch Size | Diameter | Diff |
|---|---|---|---|---|
| 15" | 325/65R15 | 31.6x12.8R15 | 803.5 mm | +0.1% |
| 16" | 305/65R16 | 31.6x12R16 | 802.9 mm | +0.0% |
| 17" | 265/70R17 | 31.6x10.4R17 | 802.8 mm | 0.0% |
| 18" | 345/50R18 | 31.6x13.6R18 | 802.2 mm | -0.1% |
| 19" | 245/65R19 | 31.5x9.6R19 | 801.1 mm | -0.2% |
| 20" | 295/50R20 | 31.6x11.6R20 | 803 mm | +0.0% |
Popular Off-Road Conversions
| Inch Size | Nearest Metric | Common Use |
|---|---|---|
| 31x10.5R15 | 265/75R15 | Jeep Wrangler, off-road |
| 33x12.5R15 | 315/70R15 | Off-road trucks, Jeeps |
| 35x12.5R17 | 315/70R17 | Lifted trucks, rock crawling |
| 33x12.5R17 | 315/70R17 | Moderate lift trucks |
| 37x12.5R17 | 315/70R17 | Heavy lift, extreme off-road |
| 31x10.5R15 | 265/75R15 | Classic off-road |
| 32x11.5R15 | 295/75R15 | Off-road, overlanding |
| 35x12.5R15 | 315/75R15 | Competition off-road |
| 33x10.5R15 | 265/70R15 | Trail driving |
| 30x9.5R15 | 235/75R15 | Light off-road, daily driving |
How to Use This Converter
This tool converts tire sizes between the two common formats: metric (e.g., 265/70R17) and inch (e.g., 31.6x10.4R17). Select your preferred conversion direction using the tabs above.
Metric to Inch: Select the width, aspect ratio, and rim diameter from the dropdowns. The converter instantly calculates the inch equivalent and shows full specifications for the tire.
Inch to Metric: Select the overall diameter, width, and rim diameter in inches. The converter finds the closest standard metric size and displays complete specifications.
Conversion Formulas
Overall Diameter (in) = ((Width mm × Aspect Ratio ÷ 100 × 2) + (Rim × 25.4)) ÷ 25.4
Width (in) = Width mm ÷ 25.4
Inch to Metric:
Width (mm) = Width in × 25.4 (rounded to nearest standard)
Sidewall (mm) = (Overall Diameter in − Rim in) ÷ 2 × 25.4
Aspect Ratio = Sidewall mm ÷ Width mm × 100 (rounded to nearest standard)
Example
A popular off-road tire like the 33x12.5R15 has an overall diameter of 33 inches and a width of 12.5 inches on a 15-inch rim. Converting to metric: width = 12.5 × 25.4 = 317.5mm (nearest standard: 315mm), sidewall = (33 - 15) / 2 = 9" = 228.6mm, aspect ratio = 228.6 / 315 × 100 = 72.6 (nearest standard: 70). The metric equivalent is approximately 315/70R15.