225/40R18
225/40R18 ships as an OEM size on the Kia Forte, Subaru Impreza, Toyota Corolla. At 25.09″ diameter with a 3.54″ sidewall (40% of section width), this size turns 804 revolutions per mile.
About 225/40R18
Factory fitments for 225/40R18 include the Kia Forte, Subaru Impreza, Toyota Corolla — meaning replacement tires in this size see steady demand and broad brand availability. At 25.09″ overall diameter, 225/40R18 turns 804 revolutions per mile, which is the reference point the factory speedometer and odometer were calibrated against. The 40% aspect ratio gives it a low-profile sidewall that delivers sharp steering response but transmits road imperfections. The 18″ rim pairing is typical for full-size truck, premium SUV, and sport-sedan platforms, so compatible wheels are easy to source new or used. Going one step shorter to 215/40R18 drops diameter by 1.26%, which stays within the ±3% fitment safe zone for most vehicles. Stepping up to 235/40R18 adds 1.26% diameter — also inside the safe window, with marginally taller ride height. If you are shopping for a direct replacement, any tire within roughly ±0.7″ of the 25.09″ stock diameter (about ±2% in percentage terms) will keep ABS, TPMS, and odometer readings inside the vehicle's designed tolerance.
Compare with another size
275/65R18 or "33" for inch aliases225/40R18
- Diameter
- 25.09″ / 637.2mm
- Section Width
- 8.86″
- Sidewall
- 3.54″ / 90mm
- Circumference
- 78.81″
- Revs/Mile
- 804
215/40R18
- Diameter
- 24.77″ / 629.2mm
- Section Width
- 8.46″
- Sidewall
- 3.39″ / 86mm
- Circumference
- 77.82″
- Revs/Mile
- 814
Speedometer & Diameter Impact
At an indicated 60 mph, your actual speed is 59.25 mph (95.35 km/h). Your speedometer reads 1.26% high versus actual speed.