TireSizesFinder

275/65R18 vs 33x12.50R18

33x12.50R18 is 0.93 in (23.5 mm) taller than 275/65R18, a +2.88% diameter difference. With the speedometer set for 275/65R18, an indicated 60 mph is 61.7 mph on 33x12.50R18.

Is this a safe swap?

Diameter difference +2.88%: within the ±3% guideline

By overall diameter alone, 33x12.50R18 falls inside the ±3% range commonly used as a guideline when replacing 275/65R18. This check uses diameter only. It does not assess load index, speed rating, wheel width or clearance.

To-scale drawing: 275/65R18 (32.07 in) vs 33x12.50R18 (33.00 in)275/65R1832.07 in × 10.83 in33x12.50R1833.00 in × 12.50 in
Side profile and tread width, drawn to the same scale.
275/65R18 vs 33x12.50R18 differences
Measurement275/65R1833x12.50R18Difference% diff
Overall diameter32.07 in (814.7 mm)33.00 in (838.2 mm)+0.93 in (+23.5 mm)+2.88%
Sidewall height7.04 in (178.8 mm)7.50 in (190.5 mm)+0.46 in (+11.8 mm)+6.57%
Section width10.83 in (275.0 mm)12.50 in (317.5 mm)+1.67 in (+42.5 mm)+15.45%
Circumference100.77 in (2,559.5 mm)103.67 in (2,633.3 mm)+2.91 in (+73.8 mm)+2.88%
Revolutions per mile629611−18−2.80%
True speed with the speedometer calibrated for 275/65R18
IndicatedActual on 275/65R18Actual on 33x12.50R18Difference
30 mph30.0 mph30.9 mph+0.9 mph
60 mph60.0 mph61.7 mph+1.7 mph
75 mph75.0 mph77.2 mph+2.2 mph

Ride-height change: 33x12.50R18 raises the vehicle by 0.46 in (11.8 mm) at the axle (half the +23.5 mm diameter difference).

33x12.50R18 is 0.93 in taller than 275/65R18 and 43 mm wider, a 2.88% difference in overall diameter.

With the speedometer calibrated for 275/65R18, an indicated 60 mph is actually 61.7 mph on 33x12.50R18, and revolutions per mile change from 629 to 611.

Both sizes mount on 18-inch wheels.

Size pages

Other comparisons with 275/65R18

Other comparisons with 33x12.50R18

Source: Calculated from standard tire geometry formulas. Verified . How these numbers are calculated.