325/30R20 in inches

A 325/30R20 tire is 27.7″ tall and 12.8″ wide, and fits a 20″ wheel. In inches it is written 27.7×12.8R20.

Diameter27.68″

Width12.80″

Sidewall3.84″

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

Manufacturer data

How tall 325/30R20 tires really are

Heights published by Michelin and Toyo for all 7 tires in this size. Their published revolutions per mile work out to 26.9″ under load (below).

Real 325/30R20 tires measure 27.70–27.72″, against 27.68″ from the size code. Every one runs taller than the size code.

Height under load26.9″

Published revs per mile (750) mean the tire rolls like a 26.9″ tire on the vehicle. Use this for speedometer calibration.

Weight spread31.1–35.3 lb

The lightest (Michelin Pilot Sport Cup 2, XL) is 4.2 lb lighter per corner than the heaviest (Toyo Proxes R888R, SL).

7 tires in 325/30R20

Sort by the spec you care about.

	Load					Revs/mi	Source
Michelin Pilot Sport Cup 2Performance	XL · 106(Y)	27.70	31.1	7.2	2,094	750	Spec page
Michelin Pilot Sport Cup 2Performance	XL · 106(Y)	27.70	31.2	7.2	2,094	750	Spec page
Toyo Proxes RPerformance	SL · 102(Y)	27.70	31.8	3.7	1,874	750	Spec page
Michelin Pilot Sport Cup 2 RPerformance	SL · 102(Y)	27.70	32.2	5.5	1,874	750	Spec page
Toyo Proxes RRPerformance	SL · 102(Y)	27.72	34.0	3.6	1,874	750	Spec page
Toyo Proxes Sport RPerformance	XL · 106W	27.70	35.1	7.2	2,094	750	Spec page
Toyo Proxes R888RPerformance	SL · 102(Y)	27.72	35.3	6.3	1,874	750	Spec page

Is 325/30R20 a 28-inch tire?

≈28″

Yes. The size code works out to 27.68″, and the 7 tires here publish 27.70–27.72″, 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 325/30R20	Difference
265/35R20	27.30	-0.37″	-1.4%
235/40R20	27.40	-0.28″	-1.0%
315/30R20	27.44	-0.24″	-0.9%
275/35R20	27.58	-0.10″	-0.4%
215/45R20	27.62	-0.06″	-0.2%
245/40R20	27.72	+0.04″	+0.1%
285/35R20	27.85	+0.18″	+0.6%
335/30R20	27.91	+0.24″	+0.9%
255/40R20	28.03	+0.35″	+1.3%
295/35R20	28.13	+0.45″	+1.6%

How to read 325/30R20

How to read any tire size

How 325/30R20 102Y is printed on the sidewall. It's the most common code among the 7 tires here (4 of them); tires in this size come in other load and speed ratings too.

1325Section width

325 mm across the widest point, or 12.80 inches. Every 325 size

230Aspect ratio

A percentage, not a measurement: the sidewall is 30% as tall as the tire is wide, which is 97.5 mm or 3.84 inches.

3RConstruction

Radial construction.

420Wheel diameter

Mounts on a 20-inch wheel. Approved wheel widths run 10.5″ to 12.0″.

5102Load index

Each tire carries up to 1,874 lb (850 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

Specification	Inches	Metric
Overall diameter	27.68	703 mm
Section width	12.80	325 mm
Sidewall height	3.84	97.5 mm
Circumference	87.0	2,209 mm
Revolutions per mile (calculated, unloaded)	728.7	453 per km
Revolutions per mile (published by manufacturers)	750	466 per km
Approved wheel width	10.5–12.0	267–305 mm

Speedometer error after switching to 325/30R20

Your actual speed– mph

Questions about 325/30R20

What is 325/30R20 in inches?

27.68 inches tall, 12.80 inches wide, on a 20-inch wheel. Written in inches, that is roughly 27.7×12.8R20.

How much does a 325/30R20 tire weigh?

Between 31.1 lb and 35.3 lb for the 7 tires listed here. The lightest is the Michelin Pilot Sport Cup 2 (XL); the heaviest is the Toyo Proxes R888R (SL).

What wheel width do I need for 325/30R20?

Manufacturers approve 10.5–12.0″ wide wheels for this size.

How many revolutions per mile does a 325/30R20 make?

Published figures run 750 revolutions per mile. The calculated figure is 728.7, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 325/30R20 than 215/45R20?

0.06 inches taller on paper (27.68″ vs 27.62″), which raises the axle about 0.03″. Your speedometer will read about 0.2% slow.