Metric to Standard Tire Converter
Enter a metric tire size like 265/75R15 in the panel to instantly see the standard inch equivalent, overall diameter in inches, section width, sidewall height, and the nearest common inch tire code. Works for all passenger, truck, SUV, and off-road tire sizes.
What Is a Metric to Standard Tire Converter?
A metric to standard tire converter translates metric tire codes like 265/75R15 into the equivalent inch-format designation used for off-road, truck, and classic vehicle tires. Metric sizing states section width in millimeters and sidewall height as a percentage of width. Standard sizing states both overall diameter and section width directly in inches. Because the two formats express the same physical dimensions differently, conversion requires calculation — and this tool does it instantly. According to Tire and Rim Association sizing standards, both formats are recognized industry designations covering the same tire specifications.
This converter is used by truck and Jeep owners shopping for off-road tires on platforms that list by inch size, mechanics matching metric OEM tires to aftermarket inch-format catalogs, and anyone comparing tires across markets where naming conventions differ. You can also use our standard to metric tire converter for the reverse calculation, or the tire size converter to see full metric tire dimensions including circumference and revolutions per mile.
How the Metric to Standard Tire Converter Works
Entering Metric Tire Size
Use the Metric Code tab to enter the tire size exactly as printed on the sidewall, such as 265/75R15 or 315/70R17. The converter parses the section width in millimeters, aspect ratio percentage, and rim diameter in inches automatically. Switch to Manual Entry to type each field separately if you prefer. The converter accepts all standard metric tire sizes including those with ZR and B construction designations.
Reading the Standard Inch Equivalent
The result shows two values. The exact standard equivalent converts your precise metric dimensions into inches without rounding. The nearest standard inch size rounds the overall diameter and section width to the nearest 0.5 inch, which reflects how inch-format tires are manufactured and cataloged. Most tire retailers and off-road forum discussions use 0.5-inch increments when naming tires, so the rounded result is the practical size you would search for when shopping.
Metric to Standard Conversion Formulas
Converting 265/75R15 to standard inch format step by step:
Step 1 — Section Width in inches:
Width (in) = Section Width (mm) ÷ 25.4
= 265 ÷ 25.4 = 10.43 in → rounds to 10.5 in
Step 2 — Sidewall Height:
Sidewall (mm) = Width (mm) × (Aspect Ratio ÷ 100)
= 265 × (75 ÷ 100) = 198.75 mm
Sidewall (in) = 198.75 ÷ 25.4 = 7.83 in
Step 3 — Overall Diameter:
OD (in) = (2 × Sidewall in inches) + Rim Diameter (in)
= (2 × 7.83) + 15 = 30.66 in → rounds to 31 in
Standard Code:
31x10.5R15 (nearest standard) or 30.7x10.4R15 (exact)
Rounding to the nearest 0.5 inch reflects the increment steps used in commercial tire production. Exact values like 30.7x10.4R15 do not exist as commercial products, but 31x10.5R15 is a widely sold size that represents the same tire. NHTSA tire safety and sizing information provides additional guidance on tire marking and size equivalency for consumer reference.
Common Metric to Standard Tire Conversions
Popular metric tire sizes with their standard inch equivalents. Rounded column shows the nearest common commercial inch size.
| Metric Size | Exact Standard | Nearest Inch Size | OD (in) |
|---|---|---|---|
| 245/75R16 | 30.5x9.6R16 | 30.5x9.5R16 | 30.47 |
| 265/75R15 | 30.7x10.4R15 | 31x10.5R15 | 30.65 |
| 265/70R16 | 30.6x10.4R16 | 30.5x10.5R16 | 30.61 |
| 275/70R18 | 33.2x10.8R18 | 33x11R18 | 33.16 |
| 285/75R16 | 32.8x11.2R16 | 33x11R16 | 32.83 |
| 305/70R16 | 32.8x12.0R16 | 33x12R16 | 32.84 |
| 315/70R17 | 34.4x12.4R17 | 34.5x12.5R17 | 34.36 |
| 315/75R16 | 34.6x12.4R16 | 35x12.5R16 | 34.60 |
| 325/65R18 | 34.0x12.8R18 | 34x13R18 | 34.00 |
| 345/65R17 | 37.0x13.6R17 | 37x13.5R17 | 37.00 |
Understanding Both Tire Size Formats
Metric Format Explained
The metric tire format is written as Width/AspectRatioR RimDiameter, such as 265/75R15. The first number is the section width in millimeters. The second number is the aspect ratio — the sidewall height expressed as a percentage of the section width. R indicates radial construction. The final number is the rim diameter in inches. The metric format does not directly state the overall tire diameter; that must be calculated. Metric sizing is the worldwide standard for passenger vehicles and is used universally by tire manufacturers for cataloging and testing. The width and aspect ratio format allows precise description of tire profile and handling characteristics, with lower aspect ratios indicating shorter, stiffer sidewalls suited for performance driving.
Standard Format Explained
The standard (inch) tire format is written as OverallDiameter x SectionWidth R RimDiameter, such as 31x10.5R15. All three dimensions are in inches. Overall diameter is stated directly, making it immediately clear how tall the tire is. Section width is the widest measurement of the inflated tire from sidewall to sidewall. Rim diameter is the wheel diameter the tire fits. The standard format is preferred in the off-road and truck tire market in North America because overall height directly communicates ground clearance — the most critical specification for off-road builds. According to SEMA aftermarket tire and wheel standards, both formats coexist in the aftermarket and OEM markets with full interchangeability when dimensions match.
When to Use Each
Use metric sizing when searching for passenger car tires, shopping at mainstream tire retailers, comparing performance tires by profile, or looking up OEM fitment specifications. Use standard inch sizing when shopping for off-road tires from brands like BF Goodrich, Nitto, or Mickey Thompson, when discussing tire sizes on truck and Jeep forums, or when matching tires to aftermarket wheels and lift kit fitment guides that reference inch sizes. Converting between formats lets you search across both worlds and find the broadest selection of compatible tires for any vehicle.
Metric to Standard Examples
Example 1 - Convert 265/75R15
265/75R15 is one of the most popular metric off-road sizes for trucks and SUVs on 15-inch wheels. To convert:
- Section Width: 265 ÷ 25.4 = 10.43 in → rounded to 10.5 in
- Sidewall: 265 × 0.75 = 198.75 mm ÷ 25.4 = 7.83 in
- Overall Diameter: (2 × 7.83) + 15 = 30.66 in → rounded to 31 in
- Standard equivalent: 31x10.5R15
31x10.5R15 is a widely available inch-format tire found in all-terrain and mud-terrain catalogs from most major manufacturers. When shopping at off-road retailers that catalog by inch size, searching 31x10.5R15 returns the same physical tire as 265/75R15. Always verify that the specific brand and model you choose lists the overall diameter within 1% of 30.66 inches before purchasing.
Example 2 - Convert 315/70R17
315/70R17 is a popular metric size for lifted half-ton trucks running 17-inch wheels. The conversion:
- Section Width: 315 ÷ 25.4 = 12.40 in → rounded to 12.5 in
- Sidewall: 315 × 0.70 = 220.5 mm ÷ 25.4 = 8.68 in
- Overall Diameter: (2 × 8.68) + 17 = 34.36 in → rounded to 34.5 in
- Standard equivalent: 34.5x12.5R17
34.5x12.5R17 is a common search term for this tire size on off-road platforms. Some retailers also list this size as 35x12.5R17 since the overall diameter is close to 35 inches, though 35x12.5R17 technically measures 34.8 to 35.0 inches depending on manufacturer. When fitment precision matters, always use the exact metric measurement for comparison. You can use our tire size converter to check full dimensions for any metric tire code.
FAQ
What is 265/75R15 in inches?
265/75R15 is approximately 31x10.5R15 in standard inch format. Section width = 265 ÷ 25.4 = 10.43 in (≈10.5 in). Sidewall = 265 × 0.75 ÷ 25.4 = 7.83 in. Overall diameter = (2 × 7.83) + 15 = 30.66 in (≈31 in). The nearest standard commercial size is 31x10.5R15.
How do I convert metric tire size to standard?
Divide section width by 25.4 to get width in inches. Multiply section width (mm) by aspect ratio divided by 100 to get sidewall in mm, then divide by 25.4 for inches. Calculate overall diameter as (2 × sidewall in inches) + rim diameter. Round both overall diameter and section width to the nearest 0.5 inch for the commercial inch size. Enter your tire in the converter above for an instant result.
What is the overall diameter of my metric tire?
Overall diameter = (2 × sidewall height in inches) + rim diameter. Sidewall = section width (mm) × (aspect ratio ÷ 100) ÷ 25.4. For 285/75R16: sidewall = 285 × 0.75 ÷ 25.4 = 8.42 in; diameter = (2 × 8.42) + 16 = 32.83 in. Use the converter above for any metric size.
Can I switch from metric to standard tires?
Yes, as long as the overall diameter and rim diameter match. The two formats are naming conventions for the same physical tire. Verify the overall diameter is within 3% of your factory specification to avoid speedometer error, ABS sensor issues, and wheel well clearance problems. Use this converter to find the matching inch size, then confirm fitment with your tire dealer.
How do I compare tire sizes?
Convert both tires to the same format using this converter, then compare overall diameter. The overall diameter is the most critical measurement for fitment compatibility, speedometer accuracy, and ground clearance. Section width affects traction and clearance at the wheel arch. A difference of more than 3% in overall diameter between original and replacement tires can cause fitment and calibration issues.