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Offroaders Staff Technical & Info
Offroaders. com Guide to P-Metric Tire Sizes, Conversion Chart and Tire Terminology – P-Metric to Inches
The following chart lists common p-metric tires sizes and the converted tread width and the actual tire height in inches. The values shown are calculated measurements based on the p-metric formula, which is explained below on this page. This chart is for an estimated conversion and the actual advertised tire height and tread width will vary from manufacturer to manufacturer. If you need to know the actual p-metric tire size and the equivalent measurements in inches for a specific tire, check with the manufacturer’s actual dimensions per individual tire brand before purchasing.
| Rim Size | P-Metric Size | Tread Width | Actual Tire Height |
| 15 Inch | 205/70R15 | 8. 0 inches | 26.3 inches |
| 215/75R15 | 8.46 inches | 27.7 inches | |
| 235/75R15 | 9.25 inches | 28.9 inches | |
| 265/70R15 | 10.4 inches | 29.6 inches | |
| 16 Inch | 225/75R16 | 8.8 inches | 29.3 inches |
| 235/85R16 | 9.25 inches | 31.7 inches | |
| 245/75R16 | 9. 6 inches | 30.5 inches | |
| 265/70R16 | 10.4 inches | 30.6 inches | |
| 265/75R16 | 10.4 inches | 31.6 inches | |
| 285/75R16 | 11.2 inches | 32.8 inches | |
| 305/70R16 | 12.0 inches | 32.8 inches | |
| 315/75R16 | 12.4 inches | 34.6 inches | |
| 345/75R16 | 13.6 inches | 36.
4 inches | |
| 17 Inch | 235/65R17 | 9.25 inches | 29.0 inches |
| 245/70R17 | 9.6 inches | 30.5 inches | |
| 255/75R17 | 10.0 inches | 32.0 inches | |
| 255/80R17 | 10.0 inches | 33.0 inches | |
| 265/70R17 | 10.4 inches | 31.6 inches | |
| 275/70R17 | 10. 8 inches | 32.2 inches | |
| 285/70R17 | 11.2 inches | 32.7 inches | |
| 285/75R17 | 11.2 inches | 33.8 inches | |
| 305/65R17 | 12.0 inches | 32.6 inches | |
| 315/70R17 | 12.4 inches | 34.4 inches | |
| 18 Inch | 265/60R18 | 10.4 inches | 30.5 inches |
| 275/65R18 | 10. 8 inches | 32.1 inches | |
| 275/70R18 | 10.8 inches | 33.2 inches | |
| 285/75R18 | 11.2 inches | 34.8 inches | |
| 295/65R18 | 12.6 inches | 33.1 inches | |
| 305/60R18 | 12.0 inches | 32.4 inches | |
| 305/70R18 | 12.0 inches | 34.8 inches | |
| 20 Inch | 275/60R20 | 10. 8 inches | 33.0 inches |
| 275/65R20 | 10.8 inches | 34.0 inches | |
| 285/60R20 | 11.2 inches | 33.4 inches | |
| 285/65R20 | 11.2 inches | 34.5 inches | |
| 295/55R20 | 12.6 inches | 32.8 inches | |
| 295/60R20 | 11.6 inches | 33.9 inches | |
| 305/55R20 | 12.0 inches | 33. 2 inches | |
| 325/60R20 | 12.8 inches | 35.3 inches |
Other 4×4 Related Calculators
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▪ Convert P-Metric Tire to Inches
All tires are required to have certain information molded into the side of the tire in a location known as the sidewall. Some of the information is self explanatory while other information requires a little knowledge to decipher. The following will help you understand what this information means.
Tire Type – This Defines the intended proper use of the tire. P indicates this is a passenger car tire while LT indicates the tire would be for a light truck with a heavier load rating.
Tire Width – This is the width of the tire measured in millimeters from sidewall to sidewall. An example might be 215 representing 215 millimeters.
Aspect Ratio – This is the ratio of the height of the tire’s cross-section to its width. An example of this might be 65, which means that the height is equal to 65% of the tire’s width. To calculate the aspect ratio, multiple the first number (e.g. 215) by the second number with a decimal before the number (e.g. .65). Using the example numbers the tires aspect ratio would calculate as 215x.65=139.75 where 139.75 is the tires height in millimeters. This is the height of the rubber from rim to tread on one side of the tire.
To convert the aspect ratio to a full tire height in inches, do this:
Convert the above calculated tire height (aspect ratio) in millimeters to inches by multiplying the millimeters by .03937 (139.
75 x .03937 = 5.5 inches). Then take the inches and multiply by two and add the rim size. Example: 5.5 x 2 + 15 (rim size in inches) = a 26 inch tall tire.
Construction – This indicates how the how the tire was put together and will say much about the tires handling characteristics. R indicates the tire is a radial type tire. For more information about what a radial is, click here. B indicates the tire is a bias ply type tire. For more information about bias ply type tires, click here.
Wheel Diameter – This is the width of the opening in the tire where it would be mounted to a wheel. This is measured from one bead across the opening to the other side of the same bead. This measurement is in inches and an example would be 15 and indicates that this tire is for a 15 inch rim, or wheel.
Load Index – This is a number corresponds to the maximum load in pounds that a tire can support when properly inflated.
You will also find the maximum load in pounds and in kilograms molded elsewhere on the tire sidewall.
Speed Rating – This is a number that corresponds to the maximum service speed for a tire. See Chart for ratings. Note: Speed ratings are specific for passenger car tires and not light truck tires. Light truck tires (LT) are not speed rated.
Rating | Maximum Speed |
| Q | 99 mph |
| S | 112 mph |
| T | 118 mph |
| U | 124 mph |
| H | 130 mph |
| V | 149 mph |
| W | 168 mph |
| Y | 186 mph |
| Z | Above 149 mph |
Calculate
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In the table above you can see a detailed comparison of the difference in dimensions, parameters and performance between a 275/50 R20 tire and a 265/75 R20 tire. The calculation results are also presented in the form of visual models (infographics), on which the tire with the size 275/50 R20 is on top, and with the size 265/75 R20, respectively, at the bottom. The visualization was generated in two projections: lateral (left) and frontal (right). The online calculator compares tires according to the following characteristics: diameter, width, circumference, profile height, revolutions per km, ground clearance change. In addition, the potential deviation between the actual speed and the speed displayed on the speedometer is calculated, which can occur if the difference between tires 275/50 R20 and 265/75 R20 is significant. nine0009
If you want to compare other tyres, just select the required parameters in the drop-down fields and click on the green button.
| Side Comparison | Frontal comparison |
|---|---|
Tire index tables. nine0009
For example: you have a 175/70 R13 wheel on your car. Using this table, we determine the profile height of your tire 175 by 70, we get 12.2 cm. If you want to put the tire wider and leave the wheel height the same, then select a value close to 12.2 from the table.
We get the size 205/60 R13. If you want to increase the size of the disk, leaving the wheel height the same, the following calculations are necessary: 175/70 R13 the profile of this wheel according to the table is 12.2 cm, multiply it by 2 because. wheel height consists of two profile values 12.2x2=24.4 cm. Next, add the size of the disc, R13 is 13 inches, convert to cm. 13x2.54=33cm. Then add the two values 24.4+33=57.4cm. this is the full height of the wheel. Now, having done some simple calculations, you will understand that you can put 195/50 R15 or 185/60 R14, for these sizes, the wheel height is about the same - 57cm. But we should not forget that with an increase in the width of the tire, it is desirable to increase the width of the disk.
Usually, the standard wheel height on the machine can be increased by 1, maximum 2 sizes. Before you change the dimension of the wheel, you can always consult with our highly experienced specialists. In some cases, the car has regular wheels of the same radius, but different widths, and the height of the wheels must be the same. (BMW 7 SERIES front 235/50 R 18, rear 255/45 R18). For all these calculations, this table was created. nine0009
| shk | 155 | 165 | 175 | 185 | 195 | 205 | 215 | 225 | 235 | 245 | 255 | 265 | 275 | 285 | 295 | 305 | 315 | 325 |
| vp | ||||||||||||||||||
| 30 | 7. 6 | 7.9 | 8.2 | 8.5 | 8.8 | 9.1 | 9.4 | 9.7 | ||||||||||
| 35 | nine0004 | 8.2 | 8.6 | 8.9 | 9.3 | 9.6 | 10 | 10.3 | 10.7 | 11 | 11.4 | |||||||
| 40 | 8.2 | 8.6 | 9 | nine0004 9.49.8 | 10.2 | 10.6 | 11 | 11.4 | 11.8 | 12.2 | 12.6 | 13 | ||||||
| 45 | 8.8 | 9.2 | 9.7 | 10.1 | 10.6 | 11 | 11.5 | 11.9 | 12.4 | 12.8 | 13. 3 | 13.7 | 14.2 | 14.6 | ||||
| 50 | 9.8 | 10.2 | 10.7 | 11.2 | 11.7 | 12.2 | 12.7 | 13.2 | 13.7 | 14.2 | 14.7 | 15.2 | 15.7 | 16.2 | ||||
| 55 | 10.2 | 10.7 | 11.3 | 11.8 | 12.4 | 12.9 | 13.5 | 14 | 14.6 | 15.1 | 15.7 | 16.2 | 16.8 | 17.3 | 17.9 | |||
| 60 | 10.5 | 11.1 | 11.7 | 12.3 | 12.9 | 13.5 | 14.1 | 14.7 | 15.3 | 15.9 | 16.5 | 17.1 | 17. 7 | 18.3 | 18.9 | 19.5 | ||
| 65 | 10 | 10.7 | 11.4 | 12.6 | 12.8 | 13.3 | 14 | 14.6 | 15.3 | 15.9 | 16.6 | 17.2 | 17.9 | 18.5 | 19.1 | 19.8 | 20.5 | 21.1 | nine0011
| 70 | 10.8 | 11.5 | 12.2 | 12.9 | 13.6 | 14.3 | 15 | 15.7 | 16.4 | 17.1 | 17.8 | 18.5 | 19.2 | 19.9 | 20.6 | 21.3 | 22 | 22.7 |
| 75 | 11.6 | 12.4 | 13.1 | 13.9 | 14.6 | 15.4 | 16.1 | 16.8 | 17.6 | 18.4 | 19.1 | 19.9 | 20.  |
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