Inches to Metric
Tire Size Calculator
Convert American flotation sizes (33", 35", 37") into standard metric tire sizes (e.g. 285/70R17, 315/70R17). Compare exact millimeter dimensions, clearance variance, and find cheaper OEM alternatives.
🎛️ Enter Any Flotation Tire Size in Inches
Our engine scans all standard commercial metric tires and ranks the closest matches.
Because tire makers only mold standard widths (ending in 5) and ratios (ending in 0 or 5), see commercial matches below:
Closest Commercial Metric Tires AvailableSorted by closest overall match
The Conversion Formulas
Unlike American flotation sizes which give the outer diameter directly (35 × 12.50R17), metric sizes calculate sidewall height as a percentage of tread width.
Width (mm) = Width (in) × 25.4Sidewall (in) = (Diameter - Rim) ÷ 2Aspect Ratio = (Sidewall Height ÷ Width) × 100How to Read Flotation Sizes
Example: 35x12.50R17LT
- 35:Overall outer diameter of the inflated tire from ground to top (35 inches).
- 12.50:Section width from sidewall to sidewall at widest point (12.50 inches / 318 mm).
- R:Radial tire internal construction (steel belt cords).
- 17:Wheel rim diameter required in inches.
- LT:Light Truck reinforced casing (heavy ply rating for off-road/towing).
Frequently Asked Questions: Converting Inches to Metric
How do you convert tire sizes from inches to metric?▼
To convert a flotation tire (e.g. 35x12.50R17) to metric: 1) Multiply width in inches by 25.4 to get width in mm (12.50 x 25.4 = 317.5 mm, rounded to standard 315 mm). 2) Calculate sidewall height: (35.0 - 17) / 2 = 9.0 inches. 3) Calculate aspect ratio: (9.0 / 12.50) x 100 = 72% (rounded to standard 70 series). The closest commercial metric size is 315/70R17.
What is the metric equivalent of a 33x12.50 tire?▼
For 17-inch wheels, the closest metric equivalent of 33x12.50R17 is 285/70R17 (32.7" x 11.2") or 305/65R17 (32.6" x 12.0"). For 15-inch wheels, the closest match is 285/75R15 or 305/70R15.
What is the metric equivalent of a 35x12.50 tire?▼
For 17-inch wheels, the closest metric equivalent of 35x12.50R17 is 315/70R17 (34.4" x 12.4" - OEM on Raptor and Bronco Sasquatch) or 295/70R17 (33.3" x 11.6"). For 20-inch wheels, the closest match is 295/65R20 (35.1" x 11.6") or 315/60R20 (34.9" x 12.4").
Why are metric tires often better than flotation inches?▼
Metric sizes are produced in vastly higher volumes for OEM truck manufacturers, making them $30 to $60 cheaper per tire. They are also typically 5 to 10 lbs lighter (reducing heavy spinning weight so your truck accelerates easier), easier to balance, and comply with factory wheel rim widths (7.5" to 8.5") that commercial tire shops require.