255/45R21 tire size

A 255/45R21 tire is 30.04 in (762.9 mm) tall and 10.04 in (255.0 mm) wide, and turns 671 revolutions per mile.

• 30.04 inOverall diameter
• 4.52 inSidewall height
• 671Revolutions per mile
• 30.0x10.0R21Flotation equivalent

255/45R21 is a 21-inch tire with a 255 mm (10.04 in) section width and a 45% aspect ratio, giving a 4.52-inch sidewall and a flotation-style size of about 30.0x10.0R21.

Its overall diameter is 30.04 inches, so it rolls 94.4 inches per revolution and turns about 671 times per mile.

65 other sizes in this list are within 3% of that diameter.

Compare 255/45R21 with plausible swaps

• 275/50R19 vs 255/45R21 (−0.69%)
• 255/55R19 vs 255/45R21 (+0.03%)
• 235/60R19 vs 255/45R21 (+0.22%)
• 275/45R20 vs 255/45R21 (−0.97%)
• 255/50R20 vs 255/45R21 (+0.01%)
• 285/45R20 vs 255/45R21 (+0.21%)
• 235/55R20 vs 255/45R21 (+0.47%)
• 255/40R21 vs 255/45R21 (−3.34%)
• 235/45R21 vs 255/45R21 (−2.36%)
• 245/45R21 vs 255/45R21 (−1.18%)
• 315/35R21 vs 255/45R21 (−1.18%)
• 285/40R21 vs 255/45R21 (−0.20%)
• 255/45R21 vs 295/40R21 (+0.85%)
• 255/45R21 vs 265/45R21 (+1.18%)
• 255/45R21 vs 275/45R21 (+2.36%)
• 255/45R21 vs 255/50R21 (+3.34%)
• 255/45R21 vs 285/35R22 (−0.60%)
• 255/45R21 vs 255/40R22 (−0.01%)
• 255/45R21 vs 265/40R22 (+1.04%)
• 255/45R21 vs 305/35R22 (+1.23%)

Sizes within 3% of 30.04 in diameter

• 255/50R20 30.04 in (+0.01%)
• 255/40R22 30.03 in (−0.01%)
• 235/65R18 30.03 in (−0.03%)
• 255/55R19 30.04 in (+0.03%)
• 255/60R18 30.05 in (+0.04%)
• 255/65R17 30.05 in (+0.05%)
• 255/70R16 30.06 in (+0.07%)
• 30x9.50R15 30.00 in (−0.12%)
• 275/60R17 29.99 in (−0.14%)
• 285/40R21 29.98 in (−0.20%)
• 285/45R20 30.10 in (+0.21%)
• 235/60R19 30.10 in (+0.22%)
• 235/70R17 29.95 in (−0.28%)
• 275/55R18 29.91 in (−0.42%)
• 235/55R20 30.18 in (+0.47%)
• 235/75R16 29.88 in (−0.52%)
• 285/35R22 29.85 in (−0.60%)
• 275/50R19 29.83 in (−0.69%)
• 225/75R17 30.29 in (+0.84%)
• 295/40R21 30.29 in (+0.85%)
• 275/45R20 29.74 in (−0.97%)
• 265/40R22 30.35 in (+1.04%)
• 215/85R16 30.39 in (+1.18%)
• 245/45R21 29.68 in (−1.18%)
• 315/35R21 29.68 in (−1.18%)
• 265/45R21 30.39 in (+1.18%)
• 305/35R22 30.41 in (+1.23%)
• 275/40R21 29.66 in (−1.25%)
• 245/50R20 29.65 in (−1.30%)
• 265/50R20 30.43 in (+1.32%)
• 295/45R20 30.45 in (+1.39%)
• 245/55R19 29.61 in (−1.42%)
• 265/70R15 29.61 in (−1.43%)
• 305/40R20 29.61 in (−1.43%)
• 245/75R16 30.47 in (+1.44%)
• 265/55R19 30.48 in (+1.47%)
• 245/60R18 29.57 in (−1.53%)
• 245/70R17 30.50 in (+1.56%)
• 265/60R18 30.52 in (+1.61%)
• 245/65R17 29.54 in (−1.65%)
• 245/65R18 30.54 in (+1.68%)
• 265/60R17 29.52 in (−1.72%)
• 265/65R17 30.56 in (+1.76%)
• 245/70R16 29.50 in (−1.77%)
• 245/75R15 29.47 in (−1.89%)
• 265/70R16 30.61 in (+1.90%)
• 245/55R20 30.61 in (+1.91%)
• 315/30R22 29.44 in (−1.98%)
• 265/50R19 29.43 in (−2.01%)
• 265/75R15 30.65 in (+2.04%)
• 275/25R24 29.41 in (−2.07%)
• 275/40R22 30.66 in (+2.08%)
• 265/45R20 29.39 in (−2.15%)
• 265/40R21 29.35 in (−2.29%)
• 285/30R24 30.73 in (+2.32%)
• 235/45R21 29.33 in (−2.36%)
• 275/45R21 30.74 in (+2.36%)
• 265/35R22 29.30 in (−2.44%)
• 295/40R20 29.29 in (−2.48%)
• 225/75R16 29.29 in (−2.49%)
• 305/45R20 30.81 in (+2.57%)
• 275/50R20 30.83 in (+2.63%)
• 235/75R17 30.88 in (+2.81%)
• 235/55R19 29.18 in (−2.86%)
• 275/55R19 30.91 in (+2.91%)

Open 255/45R21 in the tire size calculator

Source: Calculated from standard tire geometry formulas. Verified 2026-09-27. How these numbers are calculated.