225/40R20 in inches

A 225/40R20 tire is 27.1″ tall and 8.9″ wide, and fits a 20″ wheel. In inches it is written 27.1×8.9R20.

Diameter27.09″

Width8.86″

Sidewall3.54″

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

Manufacturer data

How tall 225/40R20 tires really are

Heights published by Michelin for the one tire in this size. Their published revolutions per mile work out to 26.3″ under load (below).

The one tire listed, the Michelin Pilot Sport 4 SUV, measures 27.10″: 0.01″ taller than the size code's 27.09″.

Height under load26.3″

Published revs per mile (768) mean the tire rolls like a 26.3″ tire on the vehicle. Use this for speedometer calibration.

1 tire in 225/40R20

Sort by the spec you care about.

	Load					Revs/mi	Source
Michelin Pilot Sport 4 SUVPerformance	XL · 94Y	27.10	27.6	9.0	1,477	768	Spec page

Is 225/40R20 a 27-inch tire?

≈27″

Yes. The size code works out to 27.09″, and the 1 tire here publishes 27.10″, so people call it a 27.

All 27-inch tire sizes, on every wheel size.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

Size	Diameter ″	vs 225/40R20	Difference
335/25R20	26.59	-0.49″	-1.8%
285/30R20	26.73	-0.35″	-1.3%
245/35R20	26.75	-0.33″	-1.2%
295/30R20	26.97	-0.12″	-0.4%
255/35R20	27.03	-0.06″	-0.2%
305/30R20	27.20	+0.12″	+0.4%
265/35R20	27.30	+0.22″	+0.8%
235/40R20	27.40	+0.31″	+1.2%
315/30R20	27.44	+0.35″	+1.3%
275/35R20	27.58	+0.49″	+1.8%

How to read 225/40R20

How to read any tire size

How 225/40R20 94Y is printed on the sidewall. It's the most common code among the 1 tire here; 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

240Aspect ratio

A percentage, not a measurement: the sidewall is 40% as tall as the tire is wide, which is 90.0 mm or 3.54 inches.

3RConstruction

Radial construction.

420Wheel diameter

Mounts on a 20-inch wheel. Approved wheel widths run 7.5″ to 9.0″.

594Load index

Each tire carries up to 1,477 lb (670 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

XLExtra load

Printed after the size.

Specification	Inches	Metric
Overall diameter	27.09	688 mm
Section width	8.86	225 mm
Sidewall height	3.54	90.0 mm
Circumference	85.1	2,161 mm
Revolutions per mile (calculated, unloaded)	744.6	463 per km
Revolutions per mile (published by manufacturers)	768	477 per km
Approved wheel width	7.5–9.0	191–229 mm

Speedometer error after switching to 225/40R20

Your actual speed– mph

Questions about 225/40R20

What is 225/40R20 in inches?

27.09 inches tall, 8.86 inches wide, on a 20-inch wheel. Written in inches, that is roughly 27.1×8.9R20.

What wheel width do I need for 225/40R20?

Manufacturers approve 7.5–9.0″ wide wheels for this size.

How many revolutions per mile does a 225/40R20 make?

Published figures run 768 revolutions per mile. The calculated figure is 744.6, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 225/40R20 than 255/35R20?

0.06 inches taller on paper (27.09″ vs 27.03″), which raises the axle about 0.03″. Your speedometer will read about 0.2% slow.