255/45R19 Tire Size in Inches

Diameter, width, sidewall and the closest equivalent sizes, computed from the size code.

255/45R19
28.0" tall × 10.0" wide
On a 19-inch wheel · roughly 28.0x10.0R19 in flotation sizing
MeasurementInchesMillimetres
Overall diameter28.04712
Section width10.04255
Sidewall height4.52114.8
Wheel diameter19483
Circumference88.12237
Revolutions per mile719 (447 per km)

What 255/45R19 means

255 is the section width in millimetres (10.0 in). 45 is the aspect ratio: the sidewall is 45% as tall as the tire is wide, which works out to 114.8 mm or 4.5 in. R19 is a radial tire for a 19-inch wheel.

Overall diameter is the wheel plus two sidewalls: 19 + 2 × 4.52 = 28.0 inches. These are the nominal dimensions every maker builds to; a real 255/45R19 can measure a few tenths of an inch differently by model and inflation.

Closest equivalent sizes

Common sizes within the usual 3% of 255/45R19's overall diameter. Confirm load index, speed rating and rim width before swapping.

SizeDiameterWidthChangeSpeedometer at 60
255/40R20 new wheels 28.0 in 10.0 in -0.0% really 60.0 mph
235/65R16 new wheels 28.0 in 9.3 in -0.0% really 60.0 mph
255/30R22 new wheels 28.0 in 10.0 in -0.0% really 60.0 mph
215/65R17 new wheels 28.0 in 8.5 in -0.1% really 59.9 mph
285/40R19 28.0 in 11.2 in -0.2% really 59.9 mph
235/60R17 new wheels 28.1 in 9.3 in +0.2% really 60.1 mph

Speedometer if you switch to 285/40R19

Your speedometer stays calibrated for 255/45R19. With a shorter tire you travel slower than it shows.

Speedometer readsTrue speed
30 mph29.9 mph
45 mph44.9 mph
55 mph54.9 mph
65 mph64.9 mph
75 mph74.8 mph
Compare 255/45R19 with any size →

Shop 255/45R19 tires

Check the load index and speed rating on your door-jamb placard before you buy, especially for LT tires used for towing.

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Frequently Asked Questions

A 255/45R19 tire is 28.0 inches (712 mm) tall overall. That is the 19-inch wheel plus two sidewalls of 4.5 inches each (45% of the 255 mm section width). Expect a real tire to measure within a few tenths of an inch of this, depending on the model and inflation.

The section width is 255 mm, or 10.0 inches, measured sidewall to sidewall on the recommended rim width. The tread itself is narrower than that. In flotation sizing, 255/45R19 is roughly a 28.0x10.0R19.

255/40R20 is the closest common size, at -0.0% overall diameter (28.0 in against 28.0 in). Most makers treat about 3% as the limit for a swap without speedometer or clearance problems, but always confirm load index, speed rating and wheel width before changing size.

About 719 revolutions per mile (447 per kilometre), from its 28.0-inch rolling diameter. Real-world figures run slightly higher because a loaded tire squats. This number is what your speedometer and odometer are calibrated against.

Last updated: October 2, 2026

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Other 19-inch sizes

225/40R19 225/45R19 225/55R19 235/35R19 235/40R19 235/45R19 235/50R19 235/55R19 245/35R19 245/40R19 245/45R19 245/50R19 245/55R19 255/35R19 255/40R19 255/50R19 255/55R19 265/50R19 275/35R19 275/40R19 275/45R19 285/45R19 275/55R19 285/40R19