275/25R21 in inches

A 275/25R21 tire is 26.4″ tall and 10.8″ wide, and fits a 21″ wheel. In inches it is written 26.4×10.8R21.

Diameter26.41″

Width10.83″

Sidewall2.71″

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

Manufacturer data

How tall 275/25R21 tires really are

Heights published by Michelin for the one tire in this size. Their published revolutions per mile work out to 25.6″ under load (below).

The one tire listed, the Michelin Pilot Sport 4 S, measures 26.40″: 0.01″ shorter than the size code's 26.41″.

Height under load25.6″

Published revs per mile (787) mean the tire rolls like a 25.6″ tire on the vehicle. Use this for speedometer calibration.

1 tire in 275/25R21

Sort by the spec you care about.

	Load					Revs/mi	Source
Michelin Pilot Sport 4 SPerformance	XL · 92(Y)	26.40	24.2	9.5	1,389	787	Spec page

Is 275/25R21 a 26-inch tire?

≈26″

Close. The size code works out to 26.41″, and the 1 tire here publishes 26.40″, so people call it a 26.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

Size	Diameter ″	vs 275/25R21	Difference
265/30R20	26.26	-0.15″	-0.6%
325/25R20	26.40	-0.02″	-0.1%
235/35R20	26.48	+0.06″	+0.2%
275/30R20	26.50	+0.08″	+0.3%
335/25R20	26.59	+0.18″	+0.7%
245/30R21	26.79	+0.37″	+1.4%
295/25R21	26.81	+0.39″	+1.5%
305/25R21	27.00	+0.59″	+2.2%
255/30R21	27.02	+0.61″	+2.3%
265/30R21	27.26	+0.85″	+3.2%

How to read 275/25R21

How to read any tire size

How 275/25R21 92Y 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.

1275Section width

275 mm across the widest point, or 10.83 inches. Every 275 size

225Aspect ratio

A percentage, not a measurement: the sidewall is 25% as tall as the tire is wide, which is 68.8 mm or 2.71 inches.

3RConstruction

Radial construction.

421Wheel diameter

Mounts on a 21-inch wheel. Approved wheel widths run 10.0″ to 10.0″.

592Load index

Each tire carries up to 1,389 lb (630 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	26.41	671 mm
Section width	10.83	275 mm
Sidewall height	2.71	68.8 mm
Circumference	83.0	2,108 mm
Revolutions per mile (calculated, unloaded)	763.6	474 per km
Revolutions per mile (published by manufacturers)	787	489 per km
Approved wheel width	10.0	254 mm

Speedometer error after switching to 275/25R21

Your actual speed– mph

Questions about 275/25R21

What is 275/25R21 in inches?

26.41 inches tall, 10.83 inches wide, on a 21-inch wheel. Written in inches, that is roughly 26.4×10.8R21.

What wheel width do I need for 275/25R21?

Manufacturers approve 10.0″ wide wheels for this size.

How many revolutions per mile does a 275/25R21 make?

Published figures run 787 revolutions per mile. The calculated figure is 763.6, but manufacturers measure the tire under load, where it rolls on a smaller radius.