My Tire Guide

305/40R20 tire size

A 305/40R20 tire stands 29.6 inches tall and 12.0 inches wide, with a 4.8-inch sidewall on a 20-inch rim.

29.6″OVERALL 29.6 IN · RIM 20 IN12.0″4.8″WIDTH · SIDEWALL
Overall height
29.6 in752 mm
Section width
12.0 in305 mm
Sidewall height
4.8 in122 mm
Rim diameter
20 in508 mm
Circumference
93.0 in2362 mm
Revolutions per mile
681423 per km
Inch size
29.6x12.0R20

Compare it with any other size in the tire size calculator.

Sizes you can swap to

These 20-inch sizes are within two width steps and 3% of a 305/40R20's overall height, the usual limit before the speedometer, ABS and transmission notice. The closest is 295/40R20, 1.1% shorter (0.31 in). Wider sizes also need room in the wheel well and a rim width that suits them.

SizeHeightWidthAt 60 mph
295/40R20−1.1%−0.31 in−10 mm59.4 mph
315/40R20+1.1%+0.31 in+10 mm60.6 mph
285/45R20+1.7%+0.49 in−20 mm61.0 mph
285/40R20−2.1%−0.63 in−20 mm58.7 mph
295/45R20+2.9%+0.85 in−10 mm61.7 mph

Plus and minus sizes

Changing rim size means changing the sidewall to keep the same overall height. On 18-inch or 19-inch or 21-inch or 22-inch rims, these are the closest matches to a 305/40R20.

SizeHeightWidthAt 60 mph
295/50R18+0.0%+0.01 in−10 mm60.0 mph
295/45R19−0.5%−0.15 in−10 mm59.7 mph
275/40R21+0.2%+0.06 in−30 mm60.1 mph
275/35R22−0.1%−0.03 in−30 mm59.9 mph

Other 20-inch sizes near 305/40R20

305 mm wide, other sidewalls

40 series, other widths

See the other sizes for this rim on 20-inch tire sizes.

Shop 305/40R20 tires

These open each store's own list of 305/40R20 tires, where you can filter by type, load and speed rating.

305/40R20 questions

How tall is a 305/40R20 tire?

About 29.6 inches (752 mm) from the ground to the top of the tread, unloaded. On the vehicle, carrying weight, it sits a little lower.

What does 305/40R20 mean?

305 is the section width in millimetres (12.0 in). 40 means the sidewall is 40% of that width: 122 mm, or 4.8 in. R means radial construction, and 20 is the rim diameter in inches.

Can I use 295/40R20 instead of 305/40R20?

295/40R20 is 1.1% shorter (0.31 in) and 10 mm narrower, which is inside the usual 3% rule. With it fitted, the speedometer shows 60 mph when you are doing 59.4 mph.

What is 305/40R20 in inches?

In inch terms it is 29.6x12.0R20: 29.6 inches tall, 12.0 inches wide, for a 20-inch rim.

How many revolutions per mile does a 305/40R20 make?

About 681 turns per mile, worked out from its unloaded circumference of 93.0 inches. Makers list slightly higher numbers for their own tires, because a loaded tire rolls on a smaller radius.