225/55R18 in inches

A 225/55R18 tire is 27.7″ tall and 8.9″ wide, and fits a 18″ wheel. In inches it is written 27.7×8.9R18.

Diameter27.74″

Width8.86″

Sidewall4.87″

Drawn to scale. Nominal dimensions calculated from the size code.

Manufacturer data

How tall 225/55R18 tires really are

Heights published by BFGoodrich, General, Michelin and Toyo for all 20 tires in this size. Their published revolutions per mile work out to 26.9–27.0″ under load (below).

Real 225/55R18 tires measure 27.70–27.80″, against 27.74″ from the size code. They run both taller and shorter than the size code.

Height under load26.9–27.0″

Published revs per mile (748–749) mean the tire rolls like a 26.9–27.0″ tire on the vehicle. Use this for speedometer calibration.

Weight spread24.0–34.2 lb

The lightest (General AltiMAX RT45, SL) is 10.2 lb lighter per corner than the heaviest (BFGoodrich Trail-Terrain T/A+, XL).

20 tires in 225/55R18

Sort by the spec you care about.

	Load					Revs/mi	Source
General AltiMAX RT45Touring	SL · 98H	27.70	24.0	11.0	1,653	749	Spec page
General AltiMAX365 AWTouring	SL · 98H	27.70	24.0	11.0	1,653	749	Spec page
General AltiMAX RT45Touring	SL · 98V	27.70	24.7	11.0	1,653	749	Spec page
Michelin Primacy All SeasonTouring	SL · 98H	27.80	26.2	8.5	1,653	749	Spec page
Michelin CrossClimate2All-season	SL · 98H	27.80	26.6	10.0	1,653	749	Spec page
Michelin Defender2All-season	SL · 98V	27.76	26.6	10.5	1,653	749	Spec page
Michelin X-Ice Snow+Winter	XL · 102H	27.76	26.6	10.5	1,874	749	Spec page
BFGoodrich Advantage ControlAll-season	SL · 98V	27.76	26.9	10.5	1,653	749	Spec page
Michelin X-Ice SnowWinter	XL · 102H	27.76	26.9	10.5	1,874	749	Spec page
General AltiMAX Arctic XWinter	XL · 102T	27.70	27.2	12.0	1,874	749	Spec page
Michelin Primacy Tour A/STouring	SL · 98V	27.80	27.2	8.5	1,653	749	Spec page
Toyo Extensa A/S IIAll-season	SL · 98V	27.76	27.7	10.6	1,653	748	Spec page
Toyo Proxes G-Tour	SL · 98V	27.80	28.0	11.7	1,653	748	Spec page
Toyo Proxes ST IIIPerformance	XL · 102V	27.75	28.6	10.1	1,874	748	Spec page
Toyo Observe G3-IceWinter	XL · 102T	27.75	29.1	12.0	1,874	748	Spec page
BFGoodrich Advantage ControlAll-season	SL · 98H	27.76	29.4	11.5	1,653	749	Spec page
Toyo Open Country A/T IIIAll-terrain	XL · 102H	27.76	29.5	12.8	1,874	748	Spec page
Toyo Celsius IITouring	SL · 98V	27.76	29.9	11.1	1,653	748	Spec page
BFGoodrich Trail-Terrain T/AAll-terrain	XL · 102H	27.80	33.7	12.5	1,874	749	Spec page
BFGoodrich Trail-Terrain T/A+	XL · 102H	27.80	34.2	12.5	1,874	749	Spec page

Is 225/55R18 a 28-inch tire?

≈28″

Yes. The size code works out to 27.74″, and the 20 tires here publish 27.70–27.80″, so people call it a 28.

All 28-inch tire sizes, on every wheel size.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

Size	Diameter ″	vs 225/55R18	Difference
285/40R18	26.98	-0.77″	-2.8%
255/45R18	27.04	-0.71″	-2.6%
235/50R18	27.25	-0.49″	-1.8%
215/55R18	27.31	-0.43″	-1.6%
265/45R18	27.39	-0.35″	-1.3%
345/35R18	27.51	-0.24″	-0.9%
245/50R18	27.65	-0.10″	-0.4%
245/45R19	27.68	-0.06″	-0.2%
235/55R18	28.18	+0.43″	+1.6%
295/45R18	28.45	+0.71″	+2.6%

How to read 225/55R18

How to read any tire size

How 225/55R18 98V is printed on the sidewall. It's the most common code among the 20 tires here (7 of them); tires in this size come in other load and speed ratings too.

1225Section width

225 mm across the widest point, or 8.86 inches. Every 225 size

255Aspect ratio

A percentage, not a measurement: the sidewall is 55% as tall as the tire is wide, which is 123.8 mm or 4.87 inches.

3RConstruction

Radial construction.

418Wheel diameter

Mounts on a 18-inch wheel. Approved wheel widths run 6.0″ to 8.0″.

598Load index

Each tire carries up to 1,653 lb (750 kg) at its maximum pressure.

6VSpeed rating

Rated for up to 149 mph sustained.

Specification	Inches	Metric
Overall diameter	27.74	705 mm
Section width	8.86	225 mm
Sidewall height	4.87	123.8 mm
Circumference	87.2	2,214 mm
Revolutions per mile (calculated, unloaded)	726.9	452 per km
Revolutions per mile (published by manufacturers)	748–749	465 per km
Approved wheel width	6.0–8.0	152–203 mm

Speedometer error after switching to 225/55R18

Your actual speed– mph

Questions about 225/55R18

What is 225/55R18 in inches?

27.74 inches tall, 8.86 inches wide, on a 18-inch wheel. Written in inches, that is roughly 27.7×8.9R18.

How much does a 225/55R18 tire weigh?

Between 24.0 lb and 34.2 lb for the 20 tires listed here. The lightest is the General AltiMAX RT45 (SL); the heaviest is the BFGoodrich Trail-Terrain T/A+ (XL).

What wheel width do I need for 225/55R18?

Manufacturers approve 6.0–8.0″ wide wheels for this size.

How many revolutions per mile does a 225/55R18 make?

Published figures run 748–749 revolutions per mile. The calculated figure is 726.9, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 225/55R18 than 245/50R18?

0.10 inches taller on paper (27.74″ vs 27.65″), which raises the axle about 0.05″. Your speedometer will read about 0.4% slow.