Section Width645 mm (25.4")
Aspect Ratio43%
Rim Diameter18"
Overall Diameter1012 mm (39.8")
Sidewall Height277 mm
Circumference3179 mm
645/43R18 — Buy Tires

Everything to know about the 645/43R18 tire size

Size geometry

A 645/43R18 tire has a 645mm section width and a 43% aspect ratio, mounted on a 18-inch rim. Sidewall height works out to 277.4mm (10.92") and overall outside diameter is 1011.9mm (39.84"). At highway speed the tire completes about 315 revolutions per kilometre — your speedometer and odometer were calibrated against this number.

Direct substitute sizes

If 645/43R18 is unavailable, the closest same-diameter substitutes on the same rim are 635/44R18 and 655/42R18. Both keep your speedometer reading within 1% — safe for daily use, ABS, and stability control. Always verify load and speed ratings before swapping.

Plus / minus sizing options

For a 645/43R18 you can upsize to 655/40R19 (plus-one) to fit a larger wheel without changing the speedometer reading, or downsize to 635/46R17 (minus-one) for a softer ride or winter setup. Both stay inside the Âą3% diameter tolerance that ABS and TPMS systems expect.

Vehicle compatibility

0 vehicles in our database run the 645/43R18 tire size from the factory. Aftermarket fitment depends on rim width, offset, and clearance — match these specs to your wheel before purchasing tires.

Vehicles Using 645/43R18

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