Tire Size Calculator

Advanced worldwide tire size comparison — Metric, P-Metric, LT, Flotation & ISO standards

? How to Use This Tire Size Calculator

  1. Enter your original tire size in the first field (e.g., 225/45R17, P215/55R16, or LT265/70R17).
  2. Optionally enter a new tire size in the second field to compare two sizes side by side.
  3. Type a model year (like 2024, 2025, 2026, or any year) in the custom field for contextual insights.
  4. Click “Calculate & Compare” to see detailed results, a visual graph, and a full specification breakdown.
  5. Review the speedometer variance and dimensional differences before making tire changes.
Format: Width/AspectRim (P-metric, Euro, LT, ISO)
Leave blank to calculate single tire specs only
Type any year for context
Supports: 225/45R17 • P215/55R16 • LT265/70R17 • 33×12.50R17 • 195/65R15 91H

✓ Expert Recommendations

Stay Within 3% Diameter Difference Industry guidelines from ETRTO, TRA, and JATMA recommend keeping the overall tire diameter within ±3% of the original equipment specification. Exceeding this can affect ABS calibration, transmission shift points, and traction control systems.
Verify Load Index and Speed Rating Always ensure the replacement tire’s load index meets or exceeds the vehicle manufacturer’s requirement. This information is found on the vehicle’s door jamb placard or owner’s manual. An insufficient load index compromises safety under full vehicle load.
Check Rim Width Compatibility Every tire size has an approved rim width range. Installing a tire on a rim outside this range can cause uneven wear, poor handling, and potential bead failure. Consult the tire manufacturer’s data sheet for the specific approved rim widths.
Consider International Standards Tire sizes follow different naming conventions globally. Euro-metric (ETRTO), P-metric (TRA – North America), and JATMA (Japan) standards may have slight dimensional variations for the same labeled size. When purchasing tires internationally, verify the exact specifications with the manufacturer.
Speedometer Recalibration If you change your tire’s overall diameter by more than 2%, consider having your vehicle’s speedometer recalibrated. Many modern vehicles (especially 2020+ model years) allow electronic recalibration through the OBD-II port by a qualified technician.

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