245/30R21 in inches

A 245/30R21 tire is 26.8″ tall and 9.6″ wide, and fits a 21″ wheel. In inches it is written 26.8×9.6R21.

Diameter26.79″

Width9.65″

Sidewall2.89″

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

Manufacturer data

How tall 245/30R21 tires really are

Heights published by Michelin for the one tire in this size. Their published revolutions per mile work out to 26.0″ under load (below).

The one tire listed, the Michelin Pilot Sport 4 S, measures 26.80″: 0.01″ taller than the size code's 26.79″.

Height under load26.0″

Published revs per mile (776) mean the tire rolls like a 26.0″ tire on the vehicle. Use this for speedometer calibration.

1 tire in 245/30R21

Sort by the spec you care about.

	Load					Revs/mi	Source
Michelin Pilot Sport 4 SPerformance	XL · 91(Y)	26.80	23.9	9.5	1,356	776	Spec page

Is 245/30R21 a 27-inch tire?

≈27″

Yes. The size code works out to 26.79″, and the 1 tire here publishes 26.80″, 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 245/30R21	Difference
275/25R21	26.41	-0.37″	-1.4%
285/30R20	26.73	-0.06″	-0.2%
245/35R20	26.75	-0.04″	-0.1%
295/25R21	26.81	+0.02″	+0.1%
295/30R20	26.97	+0.18″	+0.7%
305/25R21	27.00	+0.22″	+0.8%
255/30R21	27.02	+0.24″	+0.9%
265/30R21	27.26	+0.47″	+1.8%
325/25R21	27.40	+0.61″	+2.3%
275/30R21	27.50	+0.71″	+2.6%

How to read 245/30R21

How to read any tire size

How 245/30R21 91Y 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.

1245Section width

245 mm across the widest point, or 9.65 inches. Every 245 size

230Aspect ratio

A percentage, not a measurement: the sidewall is 30% as tall as the tire is wide, which is 73.5 mm or 2.89 inches.

3RConstruction

Radial construction.

421Wheel diameter

Mounts on a 21-inch wheel. Approved wheel widths run 8.0″ to 9.0″.

591Load index

Each tire carries up to 1,356 lb (615 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	26.79	680 mm
Section width	9.65	245 mm
Sidewall height	2.89	73.5 mm
Circumference	84.2	2,138 mm
Revolutions per mile (calculated, unloaded)	752.9	468 per km
Revolutions per mile (published by manufacturers)	776	482 per km
Approved wheel width	8.0–9.0	203–229 mm

Speedometer error after switching to 245/30R21

Your actual speed– mph

Questions about 245/30R21

What is 245/30R21 in inches?

26.79 inches tall, 9.65 inches wide, on a 21-inch wheel. Written in inches, that is roughly 26.8×9.6R21.

What wheel width do I need for 245/30R21?

Manufacturers approve 8.0–9.0″ wide wheels for this size.

How many revolutions per mile does a 245/30R21 make?

Published figures run 776 revolutions per mile. The calculated figure is 752.9, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 245/30R21 than 275/25R21?

0.37 inches taller on paper (26.79″ vs 26.41″), which raises the axle about 0.19″. Your speedometer will read about 1.4% slow.