TireGeoCalcTire Size Equivalent Chart and Cross Reference
Quick answer
Nominal geometryTable example: 195/65R15 → 205/55R16 · original-size calibration assumed
- 205/55R16 diameter
- 24.88in
- Diameter change
- -0.41%
- Actual at indicated 60 mph
- 59.75mph
Calculated from size markings. Not measured rolling dimensions or vehicle fitment approval.
Use this tire size equivalent chart to compare nominal dimensions across wheel sizes. A tire cross reference is most useful when it keeps the original size visible beside every candidate. Each group uses its own reference size; do not compare rows from different groups. These are nominal geometric calculations, not vehicle fitment approval. Check the vehicle manual and exact tire and wheel specifications, including load and speed ratings, approved rim width and clearance; consult the manual for any diameter change exceeding 3%.
Cross reference by original tire size
Read every candidate against the reference in its row. Positive change means a taller assembly; negative change means a shorter one. The speed columns assume an instrument calibrated exactly to that reference.
| Tire size | Reference size | Diameter / height (mm) | Diameter / height (in) | Sidewall (mm) | Circumference (mm) | Revolutions / mile | Diameter change (%) | Actual at indicated 60 mph | Actual minus indicated (mph) | Manual check |
|---|---|---|---|---|---|---|---|---|---|---|
| 195/65R15 | 195/65R15 | 634.5 | 24.98 | 126.8 | 1993.3 | 807.4 | 0.00% | 60.00 mph | 0.00 mph | |
| 205/55R16 | 195/65R15 | 631.9 | 24.88 | 112.8 | 1985.2 | 810.7 | -0.41% | 59.75 mph | -0.25 mph | |
| 225/45R17 | 195/65R15 | 634.3 | 24.97 | 101.3 | 1992.7 | 807.6 | -0.03% | 59.98 mph | -0.02 mph | |
| 205/55R16 | 205/55R16 | 631.9 | 24.88 | 112.8 | 1985.2 | 810.7 | 0.00% | 60.00 mph | 0.00 mph | |
| 225/45R17 | 205/55R16 | 634.3 | 24.97 | 101.3 | 1992.7 | 807.6 | +0.38% | 60.23 mph | +0.23 mph | |
| 225/40R18 | 205/55R16 | 637.2 | 25.09 | 90.0 | 2001.8 | 803.9 | +0.84% | 60.50 mph | +0.50 mph | |
| 225/65R17 | 225/65R17 | 724.3 | 28.52 | 146.3 | 2275.5 | 707.3 | 0.00% | 60.00 mph | 0.00 mph | |
| 235/60R18 | 225/65R17 | 739.2 | 29.10 | 141.0 | 2322.3 | 693.0 | +2.06% | 61.23 mph | +1.23 mph | |
| 235/55R19 | 225/65R17 | 741.1 | 29.18 | 129.3 | 2328.2 | 691.2 | +2.32% | 61.39 mph | +1.39 mph | |
| 265/70R17 | 265/70R17 | 802.8 | 31.61 | 185.5 | 2522.1 | 638.1 | 0.00% | 60.00 mph | 0.00 mph | |
| 275/60R18 | 265/70R17 | 787.2 | 30.99 | 165.0 | 2473.1 | 650.7 | -1.94% | 58.83 mph | -1.17 mph | |
| 275/55R20 | 265/70R17 | 810.5 | 31.91 | 151.3 | 2546.3 | 632.0 | +0.96% | 60.58 mph | +0.58 mph |
Nominal dimensions calculated from tire size markings; rounding is for display only.
- Tire size
- 195/65R15
- Reference size
- 195/65R15
- Diameter / height (mm)
- 634.5
- Diameter / height (in)
- 24.98
- Sidewall (mm)
- 126.8
- Circumference (mm)
- 1993.3
- Revolutions / mile
- 807.4
- Diameter change (%)
- 0.00%
- Actual at indicated 60 mph
- 60.00 mph
- Actual minus indicated (mph)
- 0.00 mph
- Manual check
- Tire size
- 205/55R16
- Reference size
- 195/65R15
- Diameter / height (mm)
- 631.9
- Diameter / height (in)
- 24.88
- Sidewall (mm)
- 112.8
- Circumference (mm)
- 1985.2
- Revolutions / mile
- 810.7
- Diameter change (%)
- -0.41%
- Actual at indicated 60 mph
- 59.75 mph
- Actual minus indicated (mph)
- -0.25 mph
- Manual check
- Tire size
- 225/45R17
- Reference size
- 195/65R15
- Diameter / height (mm)
- 634.3
- Diameter / height (in)
- 24.97
- Sidewall (mm)
- 101.3
- Circumference (mm)
- 1992.7
- Revolutions / mile
- 807.6
- Diameter change (%)
- -0.03%
- Actual at indicated 60 mph
- 59.98 mph
- Actual minus indicated (mph)
- -0.02 mph
- Manual check
- Tire size
- 205/55R16
- Reference size
- 205/55R16
- Diameter / height (mm)
- 631.9
- Diameter / height (in)
- 24.88
- Sidewall (mm)
- 112.8
- Circumference (mm)
- 1985.2
- Revolutions / mile
- 810.7
- Diameter change (%)
- 0.00%
- Actual at indicated 60 mph
- 60.00 mph
- Actual minus indicated (mph)
- 0.00 mph
- Manual check
- Tire size
- 225/45R17
- Reference size
- 205/55R16
- Diameter / height (mm)
- 634.3
- Diameter / height (in)
- 24.97
- Sidewall (mm)
- 101.3
- Circumference (mm)
- 1992.7
- Revolutions / mile
- 807.6
- Diameter change (%)
- +0.38%
- Actual at indicated 60 mph
- 60.23 mph
- Actual minus indicated (mph)
- +0.23 mph
- Manual check
- Tire size
- 225/40R18
- Reference size
- 205/55R16
- Diameter / height (mm)
- 637.2
- Diameter / height (in)
- 25.09
- Sidewall (mm)
- 90.0
- Circumference (mm)
- 2001.8
- Revolutions / mile
- 803.9
- Diameter change (%)
- +0.84%
- Actual at indicated 60 mph
- 60.50 mph
- Actual minus indicated (mph)
- +0.50 mph
- Manual check
- Tire size
- 225/65R17
- Reference size
- 225/65R17
- Diameter / height (mm)
- 724.3
- Diameter / height (in)
- 28.52
- Sidewall (mm)
- 146.3
- Circumference (mm)
- 2275.5
- Revolutions / mile
- 707.3
- Diameter change (%)
- 0.00%
- Actual at indicated 60 mph
- 60.00 mph
- Actual minus indicated (mph)
- 0.00 mph
- Manual check
- Tire size
- 235/60R18
- Reference size
- 225/65R17
- Diameter / height (mm)
- 739.2
- Diameter / height (in)
- 29.10
- Sidewall (mm)
- 141.0
- Circumference (mm)
- 2322.3
- Revolutions / mile
- 693.0
- Diameter change (%)
- +2.06%
- Actual at indicated 60 mph
- 61.23 mph
- Actual minus indicated (mph)
- +1.23 mph
- Manual check
- Tire size
- 235/55R19
- Reference size
- 225/65R17
- Diameter / height (mm)
- 741.1
- Diameter / height (in)
- 29.18
- Sidewall (mm)
- 129.3
- Circumference (mm)
- 2328.2
- Revolutions / mile
- 691.2
- Diameter change (%)
- +2.32%
- Actual at indicated 60 mph
- 61.39 mph
- Actual minus indicated (mph)
- +1.39 mph
- Manual check
- Tire size
- 265/70R17
- Reference size
- 265/70R17
- Diameter / height (mm)
- 802.8
- Diameter / height (in)
- 31.61
- Sidewall (mm)
- 185.5
- Circumference (mm)
- 2522.1
- Revolutions / mile
- 638.1
- Diameter change (%)
- 0.00%
- Actual at indicated 60 mph
- 60.00 mph
- Actual minus indicated (mph)
- 0.00 mph
- Manual check
- Tire size
- 275/60R18
- Reference size
- 265/70R17
- Diameter / height (mm)
- 787.2
- Diameter / height (in)
- 30.99
- Sidewall (mm)
- 165.0
- Circumference (mm)
- 2473.1
- Revolutions / mile
- 650.7
- Diameter change (%)
- -1.94%
- Actual at indicated 60 mph
- 58.83 mph
- Actual minus indicated (mph)
- -1.17 mph
- Manual check
- Tire size
- 275/55R20
- Reference size
- 265/70R17
- Diameter / height (mm)
- 810.5
- Diameter / height (in)
- 31.91
- Sidewall (mm)
- 151.3
- Circumference (mm)
- 2546.3
- Revolutions / mile
- 632.0
- Diameter change (%)
- +0.96%
- Actual at indicated 60 mph
- 60.58 mph
- Actual minus indicated (mph)
- +0.58 mph
- Manual check
What equivalent means in this chart
Equivalent describes similar calculated overall diameter. It does not describe an identical tire. When wheel diameter increases, a shorter sidewall can keep the total height close to the original. Section width may change at the same time, altering the space needed beside the wheel. Read the width and complete size code before comparing the diameter column.
A cross reference is directional because its percentage uses the original diameter as the denominator. Compare each proposed size directly with your own original specification. Do not add rounded percentages from separate groups or assume that reversing a pair produces precisely the negative percentage.
Use the alternatives tool for your own reference
Start with the size specified for the vehicle and axle in its documentation. Find that exact code in the reference column. If it is absent, open the tire size alternatives tool linked below and use your own original. The examples here cover several different vehicle categories; their inclusion together does not imply a shared application.
Keep the complete candidate code when recording results. A matching wheel diameter alone says little about overall height because section width and aspect ratio determine sidewall height. Save the original, candidate, diameter difference and wheel requirements together.
Interpret circumference and instrument changes
Circumference and diameter change by the same percentage; geometric revolutions per mile move in the opposite direction.
With a taller tire, the speedometer reads less than actual speed in this model, assuming calibration to the original size. UK/EU requirements do not permit it to read below actual speed; existing instrument error must be checked separately.
Keep the shortlist specific to the vehicle
Check wheel width, offset, brake clearance and clearance through steering and suspension travel; keep separate front and rear specifications for staggered setups. Before comparing prices, record the exact tire model, service description and manufacturer dimensions alongside the original and candidate size codes.
Read one cross-reference group
For the 205/55R16 group, the original diameter is 631.9 mm. The 225/45R17 candidate calculates to 634.3 mm, an increase of 2.4 mm or about 0.38%. The 225/40R18 row calculates to 637.2 mm, about 0.84% above the same original. Both percentages use 631.9 as their denominator, even though the candidates use different wheel diameters.
The pickup group starts from 265/70R17 at 802.8 mm. A 275/60R18 calculates to 787.2 mm, about 1.94% shorter. At an indicated 60 mph, multiplying by 787.2 divided by 802.8 gives about 58.83 mph in the chart model. This negative change belongs to the pickup reference and cannot describe a comparison against the passenger-car original.
Frequently asked questions
Are equivalent tire sizes interchangeable?
No. Similar diameter is one comparison only. Rim compatibility, clearance and service requirements must also match the vehicle. Use the chart to shortlist dimensions and then verify the exact product and wheel.
Why are there several reference groups?
A percentage needs an original diameter. Separate groups show common comparison patterns without treating one car or pickup size as the baseline for all vehicles.
Why does reversing a comparison change the percentage?
The starting diameter is the denominator. A change from a smaller diameter to a larger one uses the smaller starting value, while the reverse uses the larger value. The millimeter difference has the same magnitude, but the percentages differ.
Continue your comparison
These are nominal geometric calculations, not vehicle fitment approval. Check the vehicle manual and exact tire and wheel specifications, including load and speed ratings, approved rim width and clearance; consult the manual for any diameter change exceeding 3%.
Reference tables: Load index chart and Speed rating chart.