Current: 225/65R17
- Sidewall
- 5.76 in
- Diameter
- 28.52 in
- Circumference
- 89.6 in
- Revs/mile
- 707
Free vehicle fitment calculator
Free Tire Size Calculator
A tire size calculator compares original and replacement tire dimensions so drivers can estimate diameter, circumference, revolutions per mile, and speedometer difference before changing sizes.
Reads sizes like
225 / 65 R17
Compare the current tire with a replacement size before buying, listing, or planning a vehicle swap.
Compare two tire sizes
Enter width, aspect ratio, and rim size for the current and replacement tire.
245/60R18 is 3.71% larger than 225/65R17. At 60 mph indicated, actual speed is 62.23 mph.
Diameter change
1.06 in
Percent change
3.71%
Actual speed
62.23 mph
Speed change
2.23 mph
Replacement: 245/60R18
- Sidewall
- 5.79 in
- Diameter
- 29.57 in
- Circumference
- 92.9 in
- Revs/mile
- 682
When to use it
Use it when comparing replacement tires, checking a wheel upgrade, or estimating how a tire change affects vehicle speed readings.
What it includes
The calculator includes tire diameter, sidewall height, circumference, revolutions per mile, diameter percent change, and actual speed estimate.
Coordinate every ride
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Start a carpoolTire Size Calculator FAQ
What is a tire size calculator?
A tire size calculator compares two tire sizes and shows how the change affects diameter, circumference, revolutions per mile, and speedometer readings.
How do you read 225/65R17 tire size?
225 is the tire width in millimeters, 65 is the sidewall aspect ratio, and 17 is the wheel rim diameter in inches.
How much tire size difference is acceptable?
Many drivers try to stay within about 3% of the original tire diameter, but clearance, load rating, and manufacturer guidance matter too.
Why does tire size affect speedometer accuracy?
A larger tire travels farther per rotation, so the vehicle moves faster than the speedometer shows. A smaller tire does the opposite.