GarageCalc What 215/75R15 means
215 is the section width in millimeters (8.5 in). 75 is the aspect ratio: the sidewall is 75 percent of the width, so 215 × 0.75 = 161 mm (6.3 in). R is radial construction, and 15 is the wheel diameter in inches (381 mm). Stack two sidewalls on the wheel and you get the overall diameter: 381 + 2 × 161 = 704 mm, or 27.7 in.
A full marking adds a load index and speed rating after the size, for example 215/75R15 91V. Those two codes set how much weight and speed the tire is certified for; look them up in the load index chart and the speed rating chart.
Plus and minus sizing from 215/75R15
Going up one wheel size, the closest match is 215/70R16 at +0.6% diameter with a 151 mm sidewall instead of 161 mm. No common 14-inch size stays within 3 percent either. Anything inside 3 percent keeps the speedometer, ABS and gearing effectively stock; the comparison calculator shows the full speedometer table for any pair.
Frequently asked questions
How tall is a 215/75R15 tire?
27.7 inches (704 mm) in overall diameter: the 15-inch wheel (381 mm) plus two 161 mm sidewalls. Real tires land within about 1 to 2 percent of that depending on brand, tread depth and pressure.
What is 215/75R15 in inches?
27.7 x 8.5 R15: 27.7 inches tall, 8.5 inches wide, on a 15-inch wheel. The sidewall is 6.3 inches and the circumference is 87.0 inches, so the tire turns 728 times per mile.
What tire sizes are equivalent to 215/75R15?
Within 3 percent of the same diameter on the same 15-inch wheel: 235/70R15 (+0.9%), 225/70R15 (-1.1%), 205/75R15 (-2.1%); on a 16-inch wheel: 215/70R16 (+0.6%), 225/65R16 (-0.7%). The percentage is the diameter change, which is also your speedometer error.
Can I use 225/70R15 instead of 215/75R15?
Dimensionally yes: 225/70R15 is 1.1% shorter (-8 mm) and 10 mm wider, and at a true 60 mph the speedometer would read 60.6 mph. The extra width needs about 0.20 in of clearance on each side of the tire and a rim width that suits 225 mm.