# LTN <--> ISO Tire Size Convertor

Today there are two tire sizing systems in use.  The most common and widely uses is called the ISO Metric system, which we refer to as ISO.  The other is the Light Truck Notation system or Light Truck High Flotation system which we simply refer to here as LTN.

### ISO Metric System

The ISO system typically has three parts to it:  Tire width, measured in millimeters; the Aspect Ratio, which is a percentage use to calculate the height of the sidewall from the width; and the Rim diameter (in inches).

Typical ISO tire sizes would be:  195/65R15 or 225/50 16

These are the sizes which are uses on most passenger cars, SUV's and some light trucks.  There may, or may not be letters preceding the numbers such as P, LT, ST, or T, which indicate they type of vehicle or the use the tire was designed for.   The letter "R" may be left off, but usually is present to indicate the tire is of Radial construction. This may be changed to "B" or "D" to mean Bias-Ply or Diagonal Cord construction.

In this system all tire widths are multiples of 5, and the aspect ratios are also multiples of 5, so they will always end in a 5 or 0.

Other numbers or letters may be present on the tire following these but they do not refer to the tire size.

### LTN System

The LTN system is generally used for tires designed for light trucks and these generally have the letters LT following the series of numbers.   The numbers in this system generally has three parts to it also: the most unambiguous way of writing this is with the first two numbers separated by an "X" and the third number following a dash ( - ).

In order, they refer to

1. the overall Tire Diameter (in inches),
2. the Tire Width (in inches) and
3. the Rim Diameter, also in inches.

The typical way these sizes appear are  38 X 14.5-17  or 33 X 12.5-16.5

### Using the Convertor

This tire size converter will help you to find the equivalent tire size in either the LTN or ISO system.   For most people there isn't a great deal of practical value in this other than knowing what their tire size would be if it were using the other system, but for people who would like to see if they could find similar tires using the other sizing system, this will provide a start.

Simply keep in mind that the results are the EQUIVALENT to the tire you enter, but the size which is calculate may not actually exist.  Use the result as a starting point to find something which will be close to what you currently have or need .

Help
 LTN - ISO Converter LTN to ISO :      ISO to LTN : Convert LTN to ISO LTN Tire Size : 27X8.5-14 30X9.5-15 31X10.5-15 32X11.5-15 33X9.5-15 33X10.5-15 33X12.5-15 35X12.5-15 35X13.5-15 33X12.5-16.5 35X12.5-16.5 37X12.5-16.5 33X12.5-17 35X12.5-17 37X12.5-17 37X13.5-17 38X13.5-17 38X14.5-17 39X13.5-17 40X13.5-17 40X14.5-17 42X14.5-17 33X12.5-18 35X12.5-18 36X13.5-18 37X12.5-18 38X13.5-18 38X14.5-18 38X15.5-18 40X13.5-18 40X14.5-18 33X12.5-20 35X12.5-20 35X13.5-20 37X12.5-20 37X13.5-20 38X14.5-20 38X15.5-20 40X14.5-20 40X15.5-20 42X14.5-20 37X13.5-22 37X14-24 38X14-24 Convert ISO to LTN Section Width : 145 155 165 175 185 195 205 215 225 235 245 255 265 275 285 295 305 315 325 335 345 355 365 Aspect Ratio : 20 25 30 35 40 45 50 55 60 65 70 75 80 85 Wheel Diameter : 10 12 13 14 15 16 16.5 17 17.5 18 19 19.5 20 21 22 23 23 24 25 26 28 30