How it works

TireFlows

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Result

Diameter

30.29"

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

285/40R21-1.04%305/40R21+1.04%275/45R21+1.49%275/40R21-2.08%315/40R21+2.08%285/45R21+2.66%
Width 11.61 ″Rim 21 ″Dia. 30.29 ″4.65 ″Revs/Mile 665.8Circum. 95.2″
Diameter30.29"
Width11.61"
Sidewall4.65"
Circum.95.163"
Revs/Mile665.8

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