tireheight.com

305/45R20 in inches

A 305/45R20 tire is 30.8″ tall and 12.0″ wide, and fits a 20″ wheel. In inches it is written 30.8×12.0R20.

Diameter30.81″
Width12.01″
Sidewall5.40″
305/45R20 drawn to scale: 30.81 inch diameter, 5.40 inch sidewall, 20 inch wheel, 12.01 inch tread width20″ wheel5.40″30.81″ overall12.01″ wideSide view
Drawn to scale. Nominal dimensions calculated from the size code.
Manufacturer data

How tall 305/45R20 tires really are

Heights published by Michelin for all 2 tires in this size. Their published revolutions per mile work out to 29.8″ under load (below).

Real 305/45R20 tires measure 30.80″, against 30.81″ from the size code. They run both taller and shorter than the size code.

Height under load29.8″

Published revs per mile (676) mean the tire rolls like a 29.8″ tire on the vehicle. Use this for speedometer calibration.

Weight spread36.2–37.0 lb

The lightest (Michelin Pilot Sport EV, XL) is 0.8 lb lighter per corner than the heaviest (Michelin Pilot Sport All-Season 4, XL).

2 tires in 305/45R20

Sort by the spec you care about.

LoadRevs/miSource
Michelin Pilot Sport EVPerformanceXL · 116Y30.8036.28.02,756676Spec page
Michelin Pilot Sport All-Season 4PerformanceXL · 116V30.8037.09.02,756676Spec page

Is 305/45R20 a 31-inch tire?

≈31″

Yes. The size code works out to 30.81″, and the 2 tires here publish 30.80″, so people call it a 31.

All 31-inch tire sizes, on every wheel size.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

SizeDiameter ″vs 305/45R20Difference
285/45R2030.10-0.71″-2.3%
235/55R2030.18-0.63″-2.0%
265/50R2030.43-0.37″-1.2%
295/45R2030.45-0.35″-1.2%
275/50R2030.83+0.02″+0.1%
255/55R2031.04+0.24″+0.8%
235/60R2031.10+0.30″+1.0%
285/50R2031.22+0.41″+1.3%
265/55R2031.48+0.67″+2.2%
245/60R2031.57+0.77″+2.5%

How to read 305/45R20

How to read any tire size

305/45R20 116V as printed on the tire sidewall, with each part numbered305/45R20 116V123456
How 305/45R20 116V is printed on the sidewall. It's the most common code among the 2 tires here (1 of them); tires in this size come in other load and speed ratings too.
1305Section width

305 mm across the widest point, or 12.01 inches. Every 305 size

245Aspect ratio

A percentage, not a measurement: the sidewall is 45% as tall as the tire is wide, which is 137.3 mm or 5.40 inches.

3RConstruction

Radial construction.

420Wheel diameter

Mounts on a 20-inch wheel. Approved wheel widths run 9.5″ to 11.5″.

5116Load index

Each tire carries up to 2,756 lb (1,250 kg) at its maximum pressure.

6VSpeed rating

Rated for up to 149 mph sustained.

XLExtra load

Printed after the size.

SpecificationInchesMetric
Overall diameter30.81783 mm
Section width12.01305 mm
Sidewall height5.40137.3 mm
Circumference96.82,458 mm
Revolutions per mile (calculated, unloaded)654.7407 per km
Revolutions per mile (published by manufacturers)676420 per km
Approved wheel width9.5–11.5241–292 mm

Speedometer error after switching to 305/45R20

Your actual speed– mph

Questions about 305/45R20

What is 305/45R20 in inches?

30.81 inches tall, 12.01 inches wide, on a 20-inch wheel. Written in inches, that is roughly 30.8×12.0R20.

How much does a 305/45R20 tire weigh?

Between 36.2 lb and 37.0 lb for the 2 tires listed here. The lightest is the Michelin Pilot Sport EV (XL); the heaviest is the Michelin Pilot Sport All-Season 4 (XL).

What wheel width do I need for 305/45R20?

Manufacturers approve 9.5–11.5″ wide wheels for this size.

How many revolutions per mile does a 305/45R20 make?

Published figures run 676 revolutions per mile. The calculated figure is 654.7, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 305/45R20 than 295/45R20?

0.35 inches taller on paper (30.81″ vs 30.45″), which raises the axle about 0.18″. Your speedometer will read about 1.2% slow.