TireCalc
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Nominal geometry · exact ratios

See what changes between two tire sizes.

TireCalc separates exact size-code geometry from approximate pi-based values and from real-world fitment decisions.

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Tire comparison

No vehicle or size upload
Original or placard size
mm
%
in
Comparison size
mm
%
in
Speedometer scenario
km/h

Nominal geometry is not fitment approval. Check the vehicle placard and manual, load and speed ratings, rim compatibility, clearances, and professional guidance before changing tires.

Nominal comparison

Geometry and theoretical speed

205/55 R16+≈0.3798%225/45 R17
MeasurementOriginalComparison
Sidewall height112.75 mm101.25 mm
Overall diameter631.9 mm634.3 mm
Overall diameter≈24.878 in≈24.9724 in
Approx. circumference≈1985.17 mm≈1992.71 mm
Approx. revolutions / km≈503.73≈501.83
Approx. revolutions / mile≈810.68≈807.61
Diameter difference+2.4 mm
Ground-clearance change+1.2 mm
Theoretical actual speed≈100.3798 km/h
Speed difference+≈0.3798 km/h

634.3 ÷ 631.9 × 100

≈ marks a rounded or pi-based display. Tire pressure, load, wear, tread, manufacturing tolerance and vehicle calibration can change real rolling dimensions and speed.