225/50 R16 vs 225/40 R18

225/40 R18 stays within the configured tolerance for 225/50 R16: +0.9% diameter and +0.9% speedometer effect.

Geometric comparison

225/40 R18 stays within the configured tolerance for 225/50 R16: +0.9% diameter and +0.9% speedometer effect.

Geometric comparison
Metric	This size: 225/50 R16	Alternative: 225/40 R18	Difference	Verdict
Overall diameter	24.86 in	25.09 in	+0.9%	Within tolerance
Section width	8.86 in	8.86 in	0.00 in	Computed difference
Sidewall height	4.43 in	3.54 in	-0.89 in	Computed difference
Circumference	78.09 in	78.81 in	+0.9%	Within tolerance
Speedo	0.0%	+0.9%	+0.9%	Within tolerance

Compare sizes

Current tireLooks valid

New tireLooks valid

Market

Units

Requires verificationWithin tolerance · Diameter +0.9% (+0.23 in) · US (~3%)

Requires verification · This rating covers tire geometry only, not vehicle compatibility.
Diameter +0.9% · Ride-height change +0.11 in.
Speedometer reads low · 60 mph → 60.6 mph.
Sidewall -0.89 in · Width +0.00 in.

Diameter+0.9%+0.23 in

Speedo @ 60+0.9%60 mph → 60.6 mph

Sidewall-0.89 inWidth +0.00 in

Ride-height change+0.11 inDiameter ÷ 2

How this result is calculated

Computed from nominal tire-size geometry: diameter, circumference and speedometer error. It does not check vehicle placard approval, load/speed rating, rim-width range, wheel-arch, suspension or brake clearance.

Methodology

Before fitting

Check the vehicle placard and owner’s manual first.
Match or exceed the required load index and speed rating.
Confirm rim-width range, bolt pattern, hub bore, offset and fasteners.
Inspect wheel-arch, suspension and brake clearance under real vehicle load.
Check TPMS, cold pressure and local roadworthiness rules.

Diameter: 24.86 in 25.09 in+0.23 in
Sidewall: 4.43 in 3.54 in-0.89 in
Width: 8.86 in 8.86 in+0.00 in
Circumference: 78.09 in 78.81 in+0.9%
Revs / mile: 811 804
Speedo @ 60: 60 mph 60.6 mph+0.9%
Ride-height change: 0.00 in +0.11 in
True distance per 100 indicated: 100 mi 100.9 mi+0.9%

Current — 225/50 R16
New — 225/40 R18
Grounded to the road: the axle rises +0.11 in.

Result report

225/50 R16 225/40 R18 · Requires verification · Within tolerance

Plan budget for this size: 225/40 R18

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Plan budget for this size

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Markdown link

[225/50 R16 vs 225/40 R18 Tire size comparison](https://tirefitlab.com/tire-size-calculator/?from=225%2F50+R16&to=225%2F40+R18&market=us)

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Budget$85–$120Per tire Mid-range$110–$160Per tire Premium$160–$225Per tire

Geometric estimate. Always verify physical clearance (arches, suspension, brakes) before fitting.

In-tolerance alternative sizes

In-tolerance alternative sizes
Size	Diameter	Speedo @ 100	Use this
OE `225/50R16`	+0.0%	+0.0%

225/50 R16 · 225/40 R18 · Methodology

Technical check: 2026-06-28

What changed

Checked generated routes, metadata, sitemap inclusion and localized page rendering.

Methodology