Wheels & Tires Calculators

Decode any tire size (P-metric, LT, flotation), compare two tire sizes side by side, calculate speedometer error from a tire change, find the correct wheel offset, adjust tire pressure for temperature, and verify bolt pattern compatibility — all with instant real-time results.

All Wheels & Tires Calculators

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Tire Size Calculator

Decode any tire size (P-metric, LT-metric, flotation) into actual dimensions — diameter, width, sidewall height, circumference, and revolutions per mile.

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Tire Size Comparison Calculator

Compare two tire sizes side by side — diameter difference, width difference, speedometer error, and fitment compatibility.

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Tire Size Conversion Calculator

Convert tire sizes between P-metric (225/55R17), inches (28×10.50R15), and metric (750-16) formats.

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Speedometer Error Calculator

Calculate speedometer error caused by changing tire sizes. See your actual speed vs. displayed speed at any indicated speed.

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Speedometer Gear Calculator

Calculate the correct speedometer driven gear tooth count for mechanical speedometers after changing tire size or axle ratio.

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Wheel Offset Calculator

Calculate wheel offset (ET), backspacing, and track width change when switching to different wheels. Ensure safe fender clearance.

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Tire Pressure Adjustment Calculator

Calculate the correct tire pressure adjustment for temperature changes, load variations, and altitude. PSI and bar units supported.

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Bolt Pattern / PCD Calculator

Calculate Pitch Circle Diameter (PCD) from number of bolts and measurement between them. Find compatible wheel bolt patterns.

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💡 Understanding Tire Size Notation

A tire marked 225/55R17 means: 225mm tread width, 55% aspect ratio (sidewall height is 55% of width), R for radial construction, and 17-inch rim diameter. The overall tire diameter, circumference, and revolutions per mile are calculated from these three numbers. A wider tire (larger first number) provides more grip; a lower aspect ratio (smaller second number) improves handling but reduces ride comfort.

When changing tire sizes, the critical factor is overall diameter. A 3% diameter change is the generally accepted maximum before speedometer error, ABS calibration, and fender clearance become issues. Our Tire Size Comparison Calculator shows the exact diameter difference and flags whether the change is within the safe range.

Always verify that your new wheel offset keeps the tire inside the fender well. Use the Wheel Offset Calculator to check inner and outer clearance changes before purchasing.