Tire Size Box

215/50R19 vs 315/30R20

315/30R20 compared with 215/50R19

−0.1% diameter, +3.9" width

315/30R20 is 27.44" tall vs 27.46". Within the 3% rule, so usually interchangeable.

27.5"19" rim4.2"8.5" wide
215/50R19 (solid) compared with 315/30R20 (dashed outline), drawn to scale

With 315/30R20 tires, when your speedometer says 60 mph you are really going

59.9 mph

315/30R20 is −0.02 inches (−0.1%) in overall diameter. That is within the 3% most shops and makers allow.

215/50R19315/30R20Difference%
Overall diameter27.46"27.44"−0.02"−0.1%
Section width8.46"12.40"+3.94"+46.5%
Sidewall height4.23"3.72"−0.51"−12.1%
Circumference86.28"86.21"−0.07"−0.1%
Revolutions per mile734.3735.0+0.6+0.1%

Speedometer difference

If your vehicle came with 215/50R19 and you fit 315/30R20, here is your real speed for each speedometer reading:

Speedometer showsActual speedDifference
20 mph20.0 mph0.0 mph
30 mph30.0 mph0.0 mph
40 mph40.0 mph0.0 mph
50 mph50.0 mph0.0 mph
60 mph59.9 mph−0.1 mph
65 mph64.9 mph−0.1 mph
70 mph69.9 mph−0.1 mph
75 mph74.9 mph−0.1 mph
80 mph79.9 mph−0.1 mph

Each size on its own

Questions

Which is bigger, 215/50R19 or 315/30R20?
215/50R19 is taller by 0.02 inches (27.46" vs 27.44"). 315/30R20 is wider by 3.94 inches.
Can I replace 215/50R19 with 315/30R20?
Usually, yes. The diameter difference is −0.1%, inside the 3% rule of thumb most tire shops use. Check that the wider or taller tire clears your suspension and fenders, and that its load index meets your placard.
How much will 315/30R20 change my speedometer?
When your speedometer reads 60 mph with 315/30R20 fitted (calibrated for 215/50R19), your real speed is 59.9 mph. Your odometer will over-count miles by about 0.1%.
Will 315/30R20 lift my vehicle?
Ride height changes by half the diameter difference: −0.01 inches of ground clearance at the axle.

Other comparisons