tireheight.com

225/40R18 in inches

A 225/40R18 tire is 25.1″ tall and 8.9″ wide, and fits a 18″ wheel. In inches it is written 25.1×8.9R18.

Diameter25.09″
Width8.86″
Sidewall3.54″
225/40R18 drawn to scale: 25.09 inch diameter, 3.54 inch sidewall, 18 inch wheel, 8.86 inch tread width18″ wheel3.54″25.09″ overall8.86″ wideSide view
Drawn to scale. Nominal dimensions calculated from the size code.
Manufacturer data

How tall 225/40R18 tires really are

Heights published by BFGoodrich, General, Michelin and Toyo for all 27 tires in this size. Their published revolutions per mile work out to 24.3–24.4″ under load (below).

Real 225/40R18 tires measure 25.00–25.20″, against 25.09″ from the size code. They run both taller and shorter than the size code.

  1. Michelin Pilot Sport All-Season 425.20″ +0.11″
  2. General AltiMAX Arctic X25.10″ +0.01″
  3. General AltiMAX RT4525.10″ +0.01″
  4. General AltiMAX365 AW25.10″ +0.01″
  5. General G-MAX AS0725.10″ +0.01″
  6. General G-MAX RS25.10″ +0.01″
  7. Michelin Pilot Sport 425.10″ +0.01″
  8. Michelin Pilot Sport 4 S25.10″ +0.01″
  9. Michelin Pilot Sport Cup 2 Connect25.10″ +0.01″
  10. Michelin Pilot Sport PS225.10″ +0.01″
  11. Michelin Pilot Super Sport25.10″ +0.01″
  12. Michelin Primacy All Season25.10″ +0.01″
  13. Toyo Proxes Sport 225.10″ +0.01″
  14. Toyo Proxes Sport R25.10″ +0.01″
  15. BFGoodrich Advantage Control25.08″ −0.01″
  16. BFGoodrich g-Force COMP-2 A/S PLUS25.08″ −0.01″
  17. BFGoodrich g-Force Phenom T/A25.08″ −0.01″
  18. Michelin Pilot Alpin PA425.08″ −0.01″
  19. Michelin X-Ice Snow25.08″ −0.01″
  20. Toyo Celsius II25.08″ −0.01″
  21. Toyo Celsius Sport25.08″ −0.01″
  22. Toyo Proxes Sport A/S25.08″ −0.01″
  23. Toyo Celsius25.08″ −0.01″
  24. Toyo Extensa HP II25.08″ −0.01″
  25. Toyo Observe G3-Ice25.08″ −0.01″
  26. Toyo Proxes R888R25.08″ −0.01″
  27. Michelin CrossClimate225.00″ −0.09″
Each bar runs from the size code's 25.09″ (the orange line) to the model's published height. The track spans 1.0″. Where a model comes in several load ranges, the darker part shows its range of heights; the number after the name is how many versions it comes in.
Height under load24.3–24.4″

Published revs per mile (825–829) mean the tire rolls like a 24.3–24.4″ tire on the vehicle. Use this for speedometer calibration.

Weight spread20.1–25.1 lb

The lightest (General G-MAX RS, XL) is 5.0 lb lighter per corner than the heaviest (BFGoodrich g-Force COMP-2 A/S PLUS, XL).

27 tires in 225/40R18

Sort by the spec you care about.

LoadRevs/miSource
General G-MAX RSPerformanceXL · 92Y25.1020.110.01,389828Spec page
Michelin Pilot Super SportPerformanceSL · 88Y25.1020.49.01,235829Spec page
Michelin Pilot Sport Cup 2 ConnectPerformanceXL · 92(Y)25.1020.57.21,389829Spec page
Michelin Pilot Sport 4PerformanceXL · 92Y25.1021.09.51,389829Spec page
General AltiMAX365 AWTouringXL · 92V25.1021.511.01,389828Spec page
General AltiMAX RT45TouringXL · 92V25.1021.611.01,389828Spec page
General G-MAX AS07PerformanceXL · 92W25.1021.710.01,389828Spec page
Michelin Pilot Alpin PA4WinterXL · 92V25.0821.810.51,389829Spec page
Michelin Pilot Sport PS2PerformanceXL · 92(Y)25.1021.89.51,389829Spec page
Toyo Extensa HP IIPerformanceXL · 92W25.0821.89.31,389828Spec page
Michelin Pilot Sport 4 SPerformanceXL · 92(Y)25.1022.19.51,389829Spec page
Toyo Proxes Sport 2PerformanceXL · 92Y25.1022.28.91,389828Spec page
Michelin X-Ice SnowWinterXL · 92H25.0822.310.51,389829Spec page
Toyo Celsius SportPerformanceXL · 92Y25.0822.59.31,389828Spec page
Toyo Celsius IITouringXL · 92V25.0822.911.11,389828Spec page
BFGoodrich Advantage ControlAll-seasonXL · 92W25.0822.910.51,389829Spec page
General AltiMAX Arctic XWinterXL · 92T25.1023.112.01,389828Spec page
Michelin CrossClimate2All-seasonXL · 92V25.0023.110.01,389829Spec page
Toyo CelsiusAll-weatherSL · 92V25.0823.110.31,389828Spec page
Michelin Primacy All SeasonTouringSL · 88V25.1023.28.51,235829Spec page
Toyo Proxes Sport RPerformanceXL · 92W25.1023.47.21,389828Spec page
BFGoodrich g-Force Phenom T/APerformanceXL · 92W25.0823.89.01,389829Spec page
Michelin Pilot Sport All-Season 4PerformanceXL · 92Y25.2023.810.01,389825Spec page
Toyo Proxes R888RPerformanceXL · 92Y25.0824.06.31,389828Spec page
Toyo Proxes Sport A/SPerformanceXL · 92Y25.0824.29.31,389828Spec page
Toyo Observe G3-IceWinterXL · 92T25.0824.711.31,389828Spec page
BFGoodrich g-Force COMP-2 A/S PLUSPerformanceXL · 92W25.0825.19.01,389829Spec page

Is 225/40R18 a 25-inch tire?

≈25″

Yes. The size code works out to 25.09″, and the 27 tires here publish 25.00–25.20″, so people call it a 25.

Compare with nearby sizes

Differences in overall diameter, calculated from each size code.

SizeDiameter ″vs 225/40R18Difference
285/30R1824.73-0.35″-1.4%
245/35R1824.75-0.33″-1.3%
215/40R1824.77-0.31″-1.3%
295/30R1824.97-0.12″-0.5%
255/35R1825.03-0.06″-0.2%
265/35R1825.30+0.22″+0.9%
235/40R1825.40+0.31″+1.3%
315/30R1825.44+0.35″+1.4%
275/35R1825.58+0.49″+2.0%
215/45R1825.62+0.53″+2.1%

How to read 225/40R18

How to read any tire size

225/40R18 92Y as printed on the tire sidewall, with each part numbered225/40R18 92Y123456
How 225/40R18 92Y is printed on the sidewall. It's the most common code among the 27 tires here (7 of them); tires in this size come in other load and speed ratings too.
1225Section width

225 mm across the widest point, or 8.86 inches. Every 225 size

240Aspect ratio

A percentage, not a measurement: the sidewall is 40% as tall as the tire is wide, which is 90.0 mm or 3.54 inches.

3RConstruction

Radial construction.

418Wheel diameter

Mounts on a 18-inch wheel. Approved wheel widths run 7.5″ to 9.0″.

592Load index

Each tire carries up to 1,389 lb (630 kg) at its maximum pressure.

6YSpeed rating

Rated for up to 186 mph sustained.

XLExtra load

Printed after the size. In this size the XL tires carry up to 1,389 lb each and the standard-load tires up to 1,389 lb, as published.

SpecificationInchesMetric
Overall diameter25.09637 mm
Section width8.86225 mm
Sidewall height3.5490.0 mm
Circumference78.82,002 mm
Revolutions per mile (calculated, unloaded)803.9500 per km
Revolutions per mile (published by manufacturers)825–829513–515 per km
Approved wheel width7.5–9.0191–229 mm

Speedometer error after switching to 225/40R18

Your actual speed– mph

Questions about 225/40R18

What is 225/40R18 in inches?

25.09 inches tall, 8.86 inches wide, on a 18-inch wheel. Written in inches, that is roughly 25.1×8.9R18.

How much does a 225/40R18 tire weigh?

Between 20.1 lb and 25.1 lb for the 27 tires listed here. The lightest is the General G-MAX RS (XL); the heaviest is the BFGoodrich g-Force COMP-2 A/S PLUS (XL).

What wheel width do I need for 225/40R18?

Manufacturers approve 7.5–9.0″ wide wheels for this size.

How many revolutions per mile does a 225/40R18 make?

Published figures run 825–829 revolutions per mile. The calculated figure is 803.9, but manufacturers measure the tire under load, where it rolls on a smaller radius.

How much taller is 225/40R18 than 255/35R18?

0.06 inches taller on paper (25.09″ vs 25.03″), which raises the axle about 0.03″. Your speedometer will read about 0.2% slow.