315/70R17 Tire Size in Inches

Diameter, width, sidewall and the closest equivalent sizes, computed from the size code.

315/70R17
34.4" tall × 12.4" wide
On a 17-inch wheel · roughly 34.4x12.4R17 in flotation sizing
MeasurementInchesMillimetres
Overall diameter34.36873
Section width12.40315
Sidewall height8.68220.5
Wheel diameter17432
Circumference108.02742
Revolutions per mile587 (365 per km)

What 315/70R17 means

315 is the section width in millimetres (12.4 in). 70 is the aspect ratio: the sidewall is 70% as tall as the tire is wide, which works out to 220.5 mm or 8.7 in. R17 is a radial tire for a 17-inch wheel.

Overall diameter is the wheel plus two sidewalls: 17 + 2 × 8.68 = 34.4 inches. These are the nominal dimensions every maker builds to; a real 315/70R17 can measure a few tenths of an inch differently by model and inflation.

Closest equivalent sizes

Common sizes within the usual 3% of 315/70R17's overall diameter. Confirm load index, speed rating and rim width before swapping.

SizeDiameterWidthChangeSpeedometer at 60
295/70R18 new wheels 34.3 in 11.6 in -0.3% really 59.8 mph
285/65R20 new wheels 34.6 in 11.2 in +0.7% really 60.4 mph
315/75R16 new wheels 34.6 in 12.4 in +0.7% really 60.4 mph
275/65R20 new wheels 34.1 in 10.8 in -0.8% really 59.5 mph
295/60R20 new wheels 33.9 in 11.6 in -1.2% really 59.3 mph
285/75R18 new wheels 34.8 in 11.2 in +1.4% really 60.8 mph

Speedometer if you switch to 295/70R18

Your speedometer stays calibrated for 315/70R17. With a shorter tire you travel slower than it shows.

Speedometer readsTrue speed
30 mph29.9 mph
45 mph44.9 mph
55 mph54.8 mph
65 mph64.8 mph
75 mph74.8 mph
Compare 315/70R17 with any size →

Shop 315/70R17 tires

Check the load index and speed rating on your door-jamb placard before you buy, especially for LT tires used for towing.

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Frequently Asked Questions

A 315/70R17 tire is 34.4 inches (873 mm) tall overall. That is the 17-inch wheel plus two sidewalls of 8.7 inches each (70% of the 315 mm section width). Expect a real tire to measure within a few tenths of an inch of this, depending on the model and inflation.

The section width is 315 mm, or 12.4 inches, measured sidewall to sidewall on the recommended rim width. The tread itself is narrower than that. In flotation sizing, 315/70R17 is roughly a 34.4x12.4R17.

295/70R18 is the closest common size, at -0.3% overall diameter (34.3 in against 34.4 in). Most makers treat about 3% as the limit for a swap without speedometer or clearance problems, but always confirm load index, speed rating and wheel width before changing size.

About 587 revolutions per mile (365 per kilometre), from its 34.4-inch rolling diameter. Real-world figures run slightly higher because a loaded tire squats. This number is what your speedometer and odometer are calibrated against.

Last updated: October 2, 2026

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Other 17-inch sizes

205/40R17 205/50R17 205/55R17 215/45R17 215/50R17 215/55R17 215/60R17 215/65R17 225/45R17 225/50R17 225/55R17 225/60R17 225/65R17 235/45R17 235/55R17 235/60R17 235/65R17 235/70R17 235/80R17 245/40R17 245/45R17 245/65R17 245/70R17 245/75R17 255/60R17 255/65R17 255/70R17 255/75R17 265/65R17 265/70R17 275/65R17 275/70R17 285/70R17 285/75R17 235/50R17 255/40R17 275/60R17 305/65R17