275/30R20 tire size

A 275/30R20 tire is 26.50 inches (673.0 mm) tall, 10.83 in (275 mm) wide and fits a 20-inch wheel. In inch notation it is roughly a 26.5x10.8R20.

275/30R20 dimensions
Overall diameter	26.50 in	673.0 mm
Section width	10.83 in	275 mm
Sidewall height	3.25 in	82.5 mm
Circumference	83.24 in	2,114 mm
Revolutions	761.2 per mile	473.0 per km
Rim diameter	20 in	508.0 mm

Compare 275/30R20 with another size

Current size

New size

Speed in mphkm/h

Overall diameter difference

−0.89%

60 mph on the speedometer = 59.5 mph actual

Within the ±3 % diameter range most tire fitters accept.

Ground clearance: −3.0 mm (−0.12 in)
Revolutions: 761 → 768 per mile

275/30R20 265/30R20

Side-by-side dimensions

	Current	New	Difference	%
Diameter	26.50 in	26.26 in	−0.24 in	−0.89%
Diameter	673.0 mm	667.0 mm	−6.0 mm	−0.89%
Width	10.83 in	10.43 in	−0.39 in	−3.64%
Width	275.0 mm	265.0 mm	−10.0 mm	−3.64%
Sidewall	3.25 in	3.13 in	−0.12 in	−3.64%
Sidewall	82.5 mm	79.5 mm	−3.0 mm	−3.64%
Circumference	83.24 in	82.50 in	−0.74 in	−0.89%
Revs per mile	761.2	768.0	+6.8	+0.90%

Speedometer error

Speedometer shows	Actual speed	Difference
20 mph	19.8 mph	−0.2 mph
30 mph	29.7 mph	−0.3 mph
40 mph	39.6 mph	−0.4 mph
50 mph	49.6 mph	−0.4 mph
60 mph	59.5 mph	−0.5 mph
70 mph	69.4 mph	−0.6 mph
80 mph	79.3 mph	−0.7 mph

Alternative sizes on the same 20-inch wheel

Sizes in use within ±3 % of the overall diameter of 275/30R20:

Plus and minus sizes for 275/30R20

Size	Wheel	Diameter	Difference
265/40R18	Minus 2 (18 in)	26.35 in	−0.56%
275/40R18	Minus 2 (18 in)	26.66 in	+0.62%
245/45R18	Minus 2 (18 in)	26.68 in	+0.70%
295/35R18	Minus 2 (18 in)	26.13 in	−1.38%
275/35R19	Minus 1 (19 in)	26.58 in	+0.31%
325/30R19	Minus 1 (19 in)	26.68 in	+0.68%
265/35R19	Minus 1 (19 in)	26.30 in	−0.73%
245/40R19	Minus 1 (19 in)	26.72 in	+0.83%
295/25R21	Plus 1 (21 in)	26.81 in	+1.17%
265/30R21	Plus 1 (21 in)	27.26 in	+2.88%

Vehicles approved with 275/30R20 tires

Models whose Swiss type approval lists 275/30R20 as a standard or optional size (2,190 approvals in total). Always check your own vehicle's placard or papers.

Source: Swiss Federal Roads Office (FEDRO/ASTRA), open government data. Original data (downloaded 2026-09-29). Data processed by us; errors in processing are ours, not the publisher's.

Nearby 20-inch sizes

Reading the 275/30R20 size

275 — section width in millimetres (10.83 in).
30 — aspect ratio: the sidewall is 30 % of the width, 82.5 mm.
R — radial construction (ZR on the sidewall means a high-speed rated radial; the dimensions are the same).
20 — fits a 20-inch diameter wheel.

The load index and speed rating (for example 91V) follow the size on the sidewall. They must meet at least the values on your vehicle's tire placard.