TireFitLab

265/65 R18

What size is 265/65 R18?

265/65 R18 has an overall diameter of about 31.56 in, a section width of 10.43 in and a sidewall height of 6.78 in. It turns roughly 639 times per mile. Below are the exact figures plus plus/minus sizes that stay within the selected diameter tolerance.

Geometric comparison

265/70 R17 stays within the configured tolerance for 265/65 R18: +0.1% diameter and +0.1% speedometer effect.

Geometric comparison
Metric This size: 265/65 R18 Alternative: 265/70 R17 Difference Verdict
Overall diameter 31.56 in 31.61 in +0.1% Within tolerance
Section width 10.43 in 10.43 in 0.00 in Computed difference
Sidewall height 6.78 in 7.30 in +0.52 in Computed difference
Circumference 99.16 in 99.29 in +0.1% Within tolerance
Speedo 0.0% +0.1% +0.1% Within tolerance

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What this geometry means

265/65 R18 has a taller-sidewall proportion. The marking combines nominal section width 10.43 in, sidewall ratio 65% and rim diameter 18 inches. One sidewall is 6.78 in; both sidewalls make up 43% of the 31.56 in overall diameter, while the rim makes up 57%.

Curated alternatives: 12 sizes, spanning -2.1% to +1.7% in nominal diameter versus 265/65 R18.

Width endpoints in that set are 265/70 R17 (+0.00 in) and 305/40 R22 (+1.57 in) relative to 265/65 R18.

At the nominal 99.16 in circumference, 1,000 rotations cover 2.52 km (1.56 mi); the inverse rates are 397/km and 639/mi.

The closest diameter entry is 265/70 R17 at +0.1%. Relative to 265/65 R18, it changes nominal section width by +0.00 in, each sidewall by +0.52 in and radius by +0.02 in.

Section-width mix versus 265/65 R18: 0 narrower, 1 equal-width and 11 wider entries.

This is a nominal geometry comparison only. Vehicle clearance, wheel width and offset, load and speed ratings, and manufacturer approval still require separate checks.

Specification

Specification
Overall diameter 31.56 in
Section width 10.43 in
Sidewall height 6.78 in
Circumference 99.16 in
Revolutions 397 /km · 639 /mi

In-tolerance sizes

Alternative sizes that stay within the selected diameter tolerance:

In-tolerance sizes
Size Diameter Speedo Verdict
265/70 R17 +0.1% +0.1% ✓ OK
305/40 R22 +0.1% +0.1% ✓ OK
285/60 R18 -0.3% -0.3% ✓ OK
275/45 R22 +0.6% +0.6% ✓ OK
285/50 R20 -1.1% -1.1% ✓ OK
275/55 R20 +1.1% +1.1% ✓ OK
275/65 R18 +1.6% +1.6% ✓ OK
285/45 R22 +1.7% +1.7% ✓ OK
31x10.50 R15 -1.8% -1.8% ✓ OK
31x10.50 R16 -1.8% -1.8% ✓ OK
285/40 R22 -1.9% -1.9% ✓ OK
275/55 R19 -2.1% -2.1% ✓ OK

Compare sizes

Looks valid
Looks valid
Units
Requires verificationWithin tolerance · Diameter +0.1% (+0.04 in) · US (~3%)
  • Requires verification · This rating covers tire geometry only, not vehicle compatibility.
  • Diameter +0.1% · Ride-height change +0.02 in.
  • Speedometer reads low · 60 mph → 60.1 mph.
  • Sidewall +0.52 in · Width +0.00 in.
Diameter+0.1%+0.04 in
Speedo @ 60+0.1%60 mph → 60.1 mph
Sidewall+0.52 inWidth +0.00 in
Ride-height change+0.02 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
31.56 in 31.61 in+0.04 in
Sidewall
6.78 in 7.30 in+0.52 in
Width
10.43 in 10.43 in+0.00 in
Circumference
99.16 in 99.29 in+0.1%
Revs / mile
639 638
Speedo @ 60
60 mph 60.1 mph+0.1%
Ride-height change
0.00 in +0.02 in
True distance per 100 indicated
100 mi 100.1 mi+0.1%
Δ⌀ +0.04 inΔ↔ +0.00 in
  • Current — 265/65 R18
  • New — 265/70 R17
  • Grounded to the road: the axle rises +0.02 in.

Result report

265/65 R18 265/70 R17 · Requires verification · Within tolerance

Plan budget for this size: 265/70 R17

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Plan budget for this size
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Budget$80–$115Per tireMid-range$110–$150Per tirePremium$155–$215Per tire

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

In-tolerance alternative sizes

In-tolerance alternative sizes
SizeDiameterSpeedo @ 100Use this
−1″ 285/65R17+0.1%+0.1%
OE 265/65R18+0.0%+0.0%

More tools

Last reviewed: 2026-07-22

Technical check
2026-07-22
Content updated
2026-07-22
What changed
  • Added a localized engine-derived geometry signature and matching Markdown narrative.
Methodology