285/75R18 tire size in inches
A 285/75R18 tire is 34.83 inches tall and 11.22 inches wide on a 18-inch rim. These are nominal dimensions from the official sizing formula.
| Dimension | 285/75R18 | This size vs yours | |
|---|---|---|---|
| Overall diameter UN R30 §6.1.2.1 | 34.83 in 884.7 mm | ||
| Section width UN R30 §6.1.2.1 | 11.22 in 285.0 mm | ||
| Sidewall height UN R30 §6.1.2.1 | 8.42 in 213.8 mm | ||
| Rim diameter Marked on the tire | 18 in | ||
| Circumference From diameter | 109.42 in | ||
| Revolutions per mile From diameter | 579 | ||
| Allowed real diameter UN R30 §6.1.5 | 34.33–35.50 in |
Is 285/75R18 a 35-inch tire?
Yes. At 34.83 inches tall, 285/75R18 is commonly called a 35-inch tire. Inch-class names round to the nearest inch; the true nominal height is 34.83 in, and a new tire may legally measure between 34.33 and 35.50 in.
Speedometer change
Example: if your speedometer is calibrated for 325/65R18 and you fit 285/75R18, the tire is +0.6% in diameter, so your true speed differs from the reading as shown below. Enter your current size above to see your own figures.
| Reading | True speed | Difference |
|---|---|---|
| 30 mph | 30.2 mph | +0.2 mph |
| 45 mph | 45.3 mph | +0.3 mph |
| 55 mph | 55.3 mph | +0.3 mph |
| 60 mph | 60.3 mph | +0.3 mph |
| 70 mph | 70.4 mph | +0.4 mph |
| 80 mph | 80.5 mph | +0.5 mph |
Sizes within 3% of 285/75R18
These sizes are within 3% of the diameter of 285/75R18. The 3% figure is a rule of thumb, not a regulation and not a fitment check: wheel width, offset, suspension and body clearance decide what fits. See changing tire size.
| Size | Diameter (in) | Width (in) | Change | ±3% | Ride height (in) |
|---|---|---|---|---|---|
| 305/70R17 | 33.81 | 12.01 | −2.9% | −0.51 | |
| 285/75R17 | 33.83 | 11.22 | −2.9% | −0.50 | |
| 295/60R20 | 33.94 | 11.61 | −2.6% | −0.45 | |
| 275/65R20 | 34.07 | 10.83 | −2.2% | −0.38 | |
| 295/70R18 | 34.26 | 11.61 | −1.6% | −0.29 | |
| 315/70R17 | 34.36 | 12.40 | −1.3% | −0.23 | |
| 295/75R17 | 34.42 | 11.61 | −1.2% | −0.20 | |
| 285/65R20 | 34.59 | 11.22 | −0.7% | −0.12 | |
| 315/75R16 | 34.60 | 12.40 | −0.7% | −0.11 | |
| 325/65R18 | 34.63 | 12.80 | −0.6% | −0.10 | |
| 285/75R18 | 34.83 | 11.22 | — | — | |
| 295/65R20 | 35.10 | 11.61 | +0.8% | +0.13 |
Inch equivalent of 285/75R18
In inch terms, 285/75R18 is about 34.8x11.2R18: 34.8 in tall and 11.2 in wide, a 35-inch tire.
| Inch size | Diameter (in) | Change | Width (in) | Dimensions from |
|---|---|---|---|---|
| 35x12.50R20 | 35.00 | +0.5% | 12.50 | numbers in the size |
| 35x12.50R15 | 34.53 | −0.9% | 12.52 | UN R54 table |
| 37x12.50R15 | 36.54 | +4.9% | 12.52 | UN R54 table |
How 285/75R18 is calculated
285 mm section width × 75% aspect ratio = 213.8 mm sidewall (8.42 in).
Overall diameter = rim + 2 × sidewall = 18 in + 2 × 8.42 in = 34.83 in.
Formula: UN Regulation No. 30 §2.15 and §6.1.2.1 (passenger) and UN Regulation No. 54 §6.1.2.1 (light truck). Revolutions per mile = 63,360 ÷ circumference. Full sources are listed at the end of this page.
Questions about 285/75R18
- How tall is a 285/75R18 tire?
- 34.83 inches (884.7 mm) nominal. A new tire may measure from 34.33 to 35.50 in under the official tolerance; the maker's specification gives the figure for a specific tire.
- How wide is a 285/75R18 tire?
- 11.22 inches (285.0 mm) section width. Overall width can be slightly larger; for passenger tires, US rule FMVSS 139 allows 7% over the specified width (or 10 mm, if larger, for some pressure classes).
- How many revolutions per mile does 285/75R18 make?
- About 579 nominal, from a circumference of 109.42 in. Tire makers publish measured revolutions per mile for each tire.
- Will 285/75R18 fit my vehicle?
- This page can't tell you. Check the tire size on your door-jamb placard, then confirm wheel width, offset and clearance with the tire or vehicle maker.
Related
- All 18" sizes
- All 285 mm sizes
- Tire size chart
- Wheel offset calculator
- Re-gear calculator
- Plus-size calculator
Printed from https://tiresizecalc.net/size/285-75r18/. Figures as published on 2026-11-01. The full working and the official sources are on that page.
Sources
This size is listed by the manufacturer: Goodyear Wrangler DuraTrac, checked on the manufacturer's site on 2026-11-01. The size page shows nominal figures, not that product's measurements.
- 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.
- 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.
- 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.
- 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.
- 49 CFR 571.139 - Standard No. 139; New pneumatic radial tires for light vehicles. National Highway Traffic Safety Administration (NHTSA), Code of Federal Regulations (eCFR). 49 CFR 571.139. eCFR up to date as of 2026-10-15. S6.1.2: passenger tire width up to 7 percent (or 10 mm) over the specified width. Retrieved 2026-11-01.
- 49 CFR 571.110 - Standard No. 110; Tire selection and rims for motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less. National Highway Traffic Safety Administration (NHTSA), Code of Federal Regulations, annual edition (GovInfo). 2006-10-01. S4.3: the door placard shows the original tire size. 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.