How it works

TireFlows

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Result

Diameter

30.74"

Calculated from size marking (math only) — not a fitment guarantee. How it works

Alternate Tire Sizes

Closest diameters (math only · same rim · within 3%)

Tap a size to compare it with your current size

255/50R21+0.96%265/45R21-1.15%285/45R21+1.15%295/40R21-1.47%265/50R21+2.24%255/45R21-2.31%295/45R21+2.31%285/40R21-2.5%
Width 10.83 ″Rim 21 ″Dia. 30.74 ″4.87 ″Revs/Mile 656.0Circum. 96.6″
Diameter30.74"
Width10.83"
Sidewall4.87"
Circum.96.585"
Revs/Mile656

How results are calculated

Tire dimensions are calculated from the metric size format (width / aspect ratio / rim diameter). Diameter, circumference, and revolutions per mile are derived mathematically — no fitment or vehicle data is used.

The 3% rule is a general reference for acceptable diameter difference, not a guarantee. Always check your vehicle manual or consult a tire professional.

How it works