285/40R19 Tire Size in Inches

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

285/40R19
28.0" tall × 11.2" wide
On a 19-inch wheel · roughly 28.0x11.2R19 in flotation sizing
MeasurementInchesMillimetres
Overall diameter27.98711
Section width11.22285
Sidewall height4.49114.0
Wheel diameter19483
Circumference87.92232
Revolutions per mile721 (448 per km)

What 285/40R19 means

285 is the section width in millimetres (11.2 in). 40 is the aspect ratio: the sidewall is 40% as tall as the tire is wide, which works out to 114.0 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 × 4.49 = 28.0 inches. These are the nominal dimensions every maker builds to; a real 285/40R19 can measure a few tenths of an inch differently by model and inflation.

Closest equivalent sizes

Common sizes within the usual 3% of 285/40R19's overall diameter. Confirm load index, speed rating and rim width before swapping.

SizeDiameterWidthChangeSpeedometer at 60
235/70R15 new wheels 28.0 in 9.3 in -0.1% really 59.9 mph
215/65R17 new wheels 28.0 in 8.5 in +0.1% really 60.1 mph
255/30R22 new wheels 28.0 in 10.0 in +0.2% really 60.1 mph
235/65R16 new wheels 28.0 in 9.3 in +0.2% really 60.1 mph
255/40R20 new wheels 28.0 in 10.0 in +0.2% really 60.1 mph
255/45R19 28.0 in 10.0 in +0.2% really 60.1 mph

Speedometer if you switch to 255/45R19

Your speedometer stays calibrated for 285/40R19. With a taller tire you travel faster than it shows.

Speedometer readsTrue speed
30 mph30.1 mph
45 mph45.1 mph
55 mph55.1 mph
65 mph65.1 mph
75 mph75.2 mph
Compare 285/40R19 with any size →

Shop 285/40R19 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 285/40R19 tire is 28.0 inches (711 mm) tall overall. That is the 19-inch wheel plus two sidewalls of 4.5 inches each (40% of the 285 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 285 mm, or 11.2 inches, measured sidewall to sidewall on the recommended rim width. The tread itself is narrower than that. In flotation sizing, 285/40R19 is roughly a 28.0x11.2R19.

235/70R15 is the closest common size, at -0.1% 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 721 revolutions per mile (448 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 255/45R19 255/50R19 255/55R19 265/50R19 275/35R19 275/40R19 275/45R19 285/45R19 275/55R19