225/40R18 tire size
A 225/40R18 tire is 225 mm wide with a 90.0 mm sidewall, 40% of the width, on a 18-inch rim, which puts the whole tire at 637.2 mm, or about 25.1 inches, tall. No model in our data leaves the factory on it, but it can replace the original size on 12 models within 3% of the height.
Overall height
637.2 mm
25.1 in
Sidewall
90.0 mm
40%
Circumference
2,002 mm
Revs per km
500
Actual dimensions of 225/40R18
| Section width | 225 mm (8.9 in) |
| Sidewall height | 90.0 mm (3.54 in) |
| Rim diameter | 18 in (457.2 mm) |
| Overall diameter | 637.2 mm (25.1 in) |
| Circumference | 2,002 mm |
| Revolutions per km | 500 |
| Inch notation (height x width) | 25.1x8.9R18 |
Worked out: sidewall 225 x 0.4 = 90 mm, rim 18 x 25.4 = 457.2 mm, overall 457.2 + (90 x 2) = 637.2 mm, circumference 3.1416 x 637.2 = 2,002 mm. One turn of the tire moves the car about 2.00 m, which is 500 turns per kilometer. New to sidewall codes? See how to read a tire size.
These are nominal figures from the standard formula. Real tires vary slightly by brand and squat a little under the weight of the car.
Cars fitted with 225/40R18 from the factory
No model sold in Thailand in our data leaves the factory on 225/40R18.
Cars that can switch to 225/40R18
These cars leave the factory on another size within 3% of the height of 225/40R18. Whether it fits still depends on rim width and wheel-well clearance.
| Model | Factory size | Height difference | Wheel |
|---|---|---|---|
| Honda Civic (FE)2021–present | 235/40R18 | −1.24% | Same wheel |
| Mazda32019–present | 215/45R18 | −2.07% | Same wheel |
| Toyota Veloz2022–present | 205/50R17 | +0.06% | Needs 18-inch wheels |
| Toyota Yaris ATIV HEV2025–present | 205/50R17 | +0.06% | Needs 18-inch wheels |
| BYD Dolphin2023–present | 205/50R17 | +0.06% | Needs 18-inch wheels |
| Toyota Corolla Altis2019–present | 225/45R17 | +0.46% | Needs 18-inch wheels |
| Toyota Yaris ATIV2022–present | 195/60R16 | −0.50% | Needs 18-inch wheels |
| Suzuki XL72020–present | 195/60R16 | −0.50% | Needs 18-inch wheels |
| Honda Civic (FC)2016–2021 | 215/50R17 | −1.48% | Needs 18-inch wheels |
| MG4 Electric2022–present | 215/50R17 | −1.48% | Needs 18-inch wheels |
| MG5Current model | 215/50R17 | −1.48% | Needs 18-inch wheels |
| MG3 HYBRID+Current model | 195/55R16 | +2.63% | Needs 18-inch wheels |
Sizes that can replace 225/40R18
Sizes within ±3% of the overall height of 225/40R18. “At 100 km/h” is the real speed when the speedometer reads 100.
| Size | Height | Difference | At 100 km/h | Sidewall | Match | Compare |
|---|---|---|---|---|---|---|
| 205/50R17 | 636.8 mm | −0.4 mm (−0.06%) | 99.9 km/h | 102.5 mm | Very close | Compare |
| 225/45R17 | 634.3 mm | −2.9 mm (−0.46%) | 99.5 km/h | 101.3 mm | Very close | Compare |
| 235/45R17 | 643.3 mm | +6.1 mm (+0.96%) | 101.0 km/h | 105.8 mm | Close | Compare |
| 215/40R18 | 629.2 mm | −8.0 mm (−1.26%) | 98.7 km/h | 86.0 mm | Close | Compare |
| 235/40R18 | 645.2 mm | +8.0 mm (+1.26%) | 101.3 km/h | 94.0 mm | Close | Compare |
| 245/40R17 | 627.8 mm | −9.4 mm (−1.48%) | 98.5 km/h | 98.0 mm | Close | Compare |
| 215/50R17 | 646.8 mm | +9.6 mm (+1.51%) | 101.5 km/h | 107.5 mm | Close | Compare |
| 235/35R19 | 647.1 mm | +9.9 mm (+1.55%) | 101.6 km/h | 82.3 mm | Close | Compare |
- Keeping your wheels, the closest is 215/40R18 at 629.2 mm, −8.0 mm (−1.26%) from the original. With the speedometer on 100 km/h, the car would actually be doing about 98.7 km/h. Ground clearance drops by about 4.0 mm.
- Moving up to 19-inch wheels, the closest height match is 235/35R19 (+1.55%), with the sidewall dropping from 90.0 mm to 82.3 mm.
- Going down to 17-inch wheels, 205/50R17 (−0.06%) is the closest match and raises the sidewall to 102.5 mm.
- A larger or wider tire also changes acceleration, fuel use and steering weight, so look beyond the percentage.
Buying 225/40R18 tires
Low-profile sizes are mostly performance tires and price rises with W or Y speed ratings; comfort-focused models exist in the same size if you do not drive hard.
Check the production date in the DOT code before paying.
Check current prices
Search by brand
Links open marketplace search results; prices change constantly and not every brand makes this size.
Load index and speed rating for 225/40R18
The code after the size on the sidewall, as in 225/40R18 88V, is the load index and speed symbol. The common ratings for this size:
| Version | Index | Per tire | Four tires |
|---|---|---|---|
| Standard load (SL) | 88 | 560 kg | 2,240 kg |
| Extra load (XL) | 92 | 630 kg | 2,520 kg |
The new tire's load index and speed symbol must be no lower than the door placard, and it only carries its rated load at the correct pressure.
Common speed symbols in this size
V
240 km/h
W
270 km/h
Y
300 km/h
225/40R18 questions
How tall is a 225/40R18 tire?
About 25.1 inches, or 637.2 mm, from top to bottom before it carries weight. Each sidewall is 90.0 mm tall and the tire is 225 mm (8.9 in) wide.
Which cars use 225/40R18 tires?
No car in our data is fitted with 225/40R18 from the factory, but its height is close to the original size on Honda Civic (FE), Mazda3, Toyota Veloz, Toyota Yaris ATIV HEV and BYD Dolphin, so it works as a replacement size.
Can I fit 215/40R18 instead of 225/40R18?
Size-wise, yes: the height differs by −1.26% (−8.0 mm), so an indicated 100 km/h is really about 98.7 km/h. The tread is 10 mm narrower. Check rim width and load index first.
How much weight can a 225/40R18 tire carry?
Most standard-load versions carry load index 88: 560 kg per tire, 2,240 kg across four. XL versions are rated 92, or 630 kg per tire. Look for the number after the size on the sidewall, as in 225/40R18 88V.
Other 18-inch sizes
To compare other sizes yourself, use the tire size calculator; changing rim size, try plus/minus sizing; and see speedometer error by speed.