What is 255/35R20 in inches?

A 255/35R20 tire is 27.03 inches tall and 10.0 inches wide, with a 3.51-inch sidewall, mounted on a 20-inch wheel. In metric that is 687 mm tall and 255 mm wide. The circumference is 84.91 inches.

How tall is a 255/35R20 tire?

27.03 inches, or 687 mm. That is the overall diameter, wheel included. It turns about 746 times per mile, which is what your speedometer counts.

What do the numbers in 255/35R20 mean?

255 is the tread width in millimeters, 35 is the aspect ratio — the sidewall height as a percentage of the tread width — and 20 is the wheel diameter in inches. So the sidewall is 255 × 35% = 89.3 mm tall.

255/35R20

A 255/35R20 tire is 27.03 inches tall and 10.0 inches wide, with a 3.51-inch sidewall, mounted on a 20-inch wheel.

Common fitments: Mustang Mach 1, Camaro SS

Overall diameter

27.03″

687 mm

Sidewall height

3.51″

89.3 mm

Tread width

255 mm

10.0″

Circumference

84.91″

7.1 ft

Revs per mile

746

464 per km

Wheel diameter

20″

aspect ratio 35%

Compare vs 275/55R20 Compare with a custom size

Cross-section

Overall diameter: 27.03″
Sidewall (each side): 3.51″
Wheel: 20″

255/35R20 in inches and millimeters

Every dimension of a 255/35R20, converted both ways. Calculated from the size code, accurate to about 1%.

Measurement	Inches	Millimeters
Overall diameter (height)	27.03″	687 mm
Tread width	10.0″	255 mm
Sidewall height	3.51″	89.3 mm
Wheel diameter	20″	508 mm
Circumference	84.91″	2157 mm

Nominal dimensions from the size code. A real tire varies by a few millimeters between manufacturers, and a loaded tire sits slightly shorter than its free diameter.

255/35R20 compared with other sizes

All 24 practical swaps involving 255/35R20 — diameter change, speedometer impact and a fit verdict for each.

255/35R20 → 235/50R18

235/50R18

Diameter −0.8% · This fits

255/35R20 → 245/40R19

245/40R19

Diameter +1.2% · This fits

255/35R20 → 255/40R19

255/40R19

Diameter −0.0% · This fits

255/35R20 → 245/35R20

245/35R20

Diameter +1.0% · This fits

245/35R20 → 255/35R20

245/35R20

Diameter −1.0% · This fits

265/35R20 → 255/35R20

265/35R20

Diameter +1.0% · This fits

275/35R20 → 255/35R20

275/35R20

Diameter +2.0% · This fits

245/40R20 → 255/35R20

245/40R20

Diameter +2.5% · This fits

255/40R19 → 255/35R20

255/40R19

Diameter +0.0% · This fits

255/45R18 → 255/35R20

255/45R18

Diameter +0.0% · This fits

295/35R20 → 255/35R20

295/35R20

Diameter +4.1% · Borderline. Check clearance first

235/50R18 → 255/35R20

235/50R18

Diameter +0.8% · This fits

235/45R19 → 255/35R20

235/45R19

Diameter +1.1% · This fits

245/40R19 → 255/35R20

245/40R19

Diameter −1.2% · This fits

245/45R18 → 255/35R20

245/45R18

Diameter −1.3% · This fits

235/40R19 → 255/35R20

235/40R19

Diameter −2.3% · This fits

275/40R19 → 255/35R20

275/40R19

Diameter +2.3% · This fits

245/45R19 → 255/35R20

245/45R19

Diameter +2.4% · This fits

255/35R20 → 295/35R20

295/35R20

Diameter −3.9% · Borderline. Check clearance first

255/35R20 → 255/45R18

255/45R18

Diameter −0.0% · This fits

255/35R20 → 245/40R20

245/40R20

Diameter −2.5% · This fits

255/35R20 → 265/35R20

265/35R20

Diameter −1.0% · This fits

255/35R20 → 275/35R20

275/35R20

Diameter −2.0% · This fits

255/35R20 → 275/55R20

275/55R20

Diameter −15.3% · Too big a jump

Common questions

What is 255/35R20 in inches?: A 255/35R20 tire is 27.03 inches tall and 10.0 inches wide, with a 3.51-inch sidewall, mounted on a 20-inch wheel. In metric that is 687 mm tall and 255 mm wide. The circumference is 84.91 inches.
How tall is a 255/35R20 tire?: 27.03 inches, or 687 mm. That is the overall diameter, wheel included. It turns about 746 times per mile, which is what your speedometer counts.
What do the numbers in 255/35R20 mean?: 255 is the tread width in millimeters, 35 is the aspect ratio — the sidewall height as a percentage of the tread width — and 20 is the wheel diameter in inches. So the sidewall is 255 × 35% = 89.3 mm tall.