TireSizeCalc

265/60R20 vs 275/60R20

275/60R20 is +0.47 in (+1.5%) in diameter and 0.39 in wider than 265/60R20.

Size comparison265/60R20
Dimension265/60R20 275/60R20Difference
Overall diameter
UN R30 §6.1.2.1
32.52 in 826.0 mm32.99 in 838.0 mm+0.47 in
Section width
UN R30 §6.1.2.1
10.43 in 265.0 mm10.83 in 275.0 mm+0.40 in
Sidewall height
UN R30 §6.1.2.1
6.26 in 159.0 mm6.50 in 165.0 mm+0.24 in
Rim diameter
Marked on the tire
20 in20 in0 in
Circum­ference
From diameter
102.16 in103.65 in+1.49 in
Revolutions per mile
From diameter
620611−9
Allowed real diameter
UN R30 §6.1.5
32.14–33.02 in32.60–33.51 in
Nominal, not measuredReal tires vary by brand and load range.
32.52 in
  • 265/60R20 32.52 in
  • 275/60R20 32.99 in
Drawn to scale on one ground line.

Speedometer change

mphTrue speed 60.9 mph (+0.9 mph)

If your speedometer is calibrated for 265/60R20 and you fit 275/60R20, the tire is +1.5% in diameter, so your true speed differs from the reading as shown below.

Speedometer reading versus true speed
ReadingTrue speedDifference
30 mph30.4 mph+0.4 mph
45 mph45.7 mph+0.7 mph
55 mph55.8 mph+0.8 mph
60 mph60.9 mph+0.9 mph
70 mph71.0 mph+1.0 mph
80 mph81.2 mph+1.2 mph

What changes

Nominal dimensions from the official sizing formula (sources below). This comparison doesn't check fit: wheel width, offset and clearance decide that. See changing tire size.

Each size

Sources

  1. UN Regulation No. 30 - Uniform provisions concerning the approval of pneumatic tyres for motor vehicles and their trailers (Revision 3). United Nations Economic Commission for Europe (UNECE). E/ECE/324 E/ECE/TRANS/505 Rev.1/Add.29/Rev.3. 2007-03-29. Para 2.15 and 6.1.2.1: aspect ratio and outer diameter, D = d + 2H. Retrieved 2026-11-01.
  2. UN Regulation No. 54 - Uniform provisions concerning the approval of pneumatic tyres for commercial vehicles and their trailers (Revision 2). United Nations Economic Commission for Europe (UNECE). E/ECE/324 E/ECE/TRANS/505 Rev.1/Add.53/Rev.2. 2004-04-16. Para 6.1.2.1: the same formula for light truck tires. Retrieved 2026-11-01.
  3. UN Regulation No. 30 - Uniform provisions concerning the approval of pneumatic tyres for motor vehicles and their trailers (Revision 3). United Nations Economic Commission for Europe (UNECE). E/ECE/324 E/ECE/TRANS/505 Rev.1/Add.29/Rev.3. 2007-03-29. Para 6.1.5: allowed outer diameter, Dmin = d + 2H x 0.97, Dmax = d + 2H x 1.04. Retrieved 2026-11-01.
  4. Computed by tiresizecalc.net from the cited formula. Sri Murugan Systems. Circumference = pi x diameter; revolutions per mile = 63,360 / circumference; 1 in = 25.4 mm exactly. Retrieved 2026-11-01.
  5. Computed by tiresizecalc.net from the cited formula. Sri Murugan Systems. Speedometer: true speed = indicated speed x new diameter / old diameter. Retrieved 2026-11-01.

Last reviewed 2026-11-01. The full source list, with dates and file checksums, is in How the numbers are calculated. To report an error, email contactus@tiresizecalc.net.