225/45 R18
What size is 225/45 R18?
225/45 R18 has an overall diameter of about 25.97 in, a section width of 8.86 in and a sidewall height of 3.99 in. It turns roughly 777 times per mile. Below are the exact figures plus in-tolerance plus/minus sizes you can switch to safely.
- Overall diameter: 25.97 in.
- Section width: 8.86 in.
- Sidewall height: 3.99 in.
- Revolutions: 483 /km · 777 /mi.
- In-tolerance sizes: 255/35 R19 (+0.2%).
Fitment verdict
255/35 R19 stays within the configured tolerance for 225/45 R18: +0.2% diameter and +0.2% speedometer effect.
| Metric | This size: 225/45 R18 | Alternative: 255/35 R19 | Difference | Verdict |
|---|---|---|---|---|
| Overall diameter | 25.97 in | 26.03 in | +0.2% | Within tolerance |
| Section width | 8.86 in | 10.04 in | +1.18 in | Computed difference |
| Sidewall height | 3.99 in | 3.51 in | -0.47 in | Computed difference |
| Circumference | 81.59 in | 81.77 in | +0.2% | Within tolerance |
| Speedo | 0.0% | +0.2% | +0.2% | Within tolerance |
Seasonal check
Planning a long summer drive?
Use the budget and running-cost tools before a trip, especially if the current tyres are worn or the replacement size changes diameter.
Specification
| Overall diameter | 25.97 in |
|---|---|
| Section width | 8.86 in |
| Sidewall height | 3.99 in |
| Circumference | 81.59 in |
| Revolutions | 483 /km · 777 /mi |
In-tolerance sizes
Alternative sizes that stay within the safe diameter tolerance:
| Size | Diameter | Speedo | Verdict |
|---|---|---|---|
| 255/35 R19 | +0.2% | +0.2% | ✓ OK |
| 205/55 R17 | -0.4% | -0.4% | ✓ OK |
| 225/50 R17 | -0.4% | -0.4% | ✓ OK |
| 215/60 R16 | +0.7% | +0.7% | ✓ OK |
| 245/35 R19 | -0.8% | -0.8% | ✓ OK |
| 225/55 R16 | -0.9% | -0.9% | ✓ OK |
| 245/40 R18 | -1.0% | -1.0% | ✓ OK |
| 205/60 R16 | -1.1% | -1.1% | ✓ OK |
| 245/45 R17 | -1.1% | -1.1% | ✓ OK |
| 205/70 R15 | +1.3% | +1.3% | ✓ OK |
| 215/55 R17 | +1.3% | +1.3% | ✓ OK |
| 235/45 R18 | +1.4% | +1.4% | ✓ OK |
Compare sizes
- Within tolerance · Diameter +0.2%.
- Speedo @ 60: 60 mph → 60.1 mph.
- Sidewall -0.47 in · Width +1.18 in.
How this result is calculated
Computed from nominal tire-size geometry: diameter, circumference and speedometer error. It does not check wheel-arch, suspension or brake clearance.
Methodology- Diameter
- 25.97 in 26.03 in+0.06 in
- Sidewall
- 3.99 in 3.51 in-0.47 in
- Width
- 8.86 in 10.04 in+1.18 in
- Circumference
- 81.59 in 81.77 in+0.2%
- Revs / mile
- 777 775
- Speedo @ 60
- 60 mph 60.1 mph+0.2%
- Current —
225/45 R18 - New —
255/35 R19 - Grounded to the road: the axle rises +0.03 in.
Result report
225/45 R18 255/35 R19 · Within tolerance
Use this size when shopping: 255/35 R19
Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.
Safe alternative sizes
| Size | Diameter | Speedo @ 100 | Use this |
|---|---|---|---|
−1″ 285/40R17 | +0.0% | +0.0% | |
OE 225/45R18 | +0.0% | +0.0% | |
+1″ 295/30R19 | -0.0% | -0.0% | |
+2″ 305/25R20 | +0.1% | +0.1% |
More tools
- How to read a tire size
- Plus sizing guide
- Speedometer error guide
- 225mm Section width guide
- /45 Aspect ratio guide
- Rim diameter 18"
- Load index chart
- Speed rating chart
- Rim width and tyre fitment guide
- Wheel offset guide
- Wheel spacers guide
- Tyre pressure for heavy loads and towing
What changed
- Reviewed deterministic geometry, load/speed references, sitemap inclusion and localized page shell.