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Pulse per Mile Calculator

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The pulse per mile calculator is a tool that lets you compute wheel rotation and the number of pulses per mile in the blink of an eye. These parameters are useful for several sensors in your car, such as speedometers, odometers, and cruise control.

Stay with us in this article, where you will learn about the pulse per mile formula, or what a VSS is. Prepare your drivetrain to rotate and let's compute the pulses per mile!

🙋 If you are searching for more tools related to engines, check out our turbo size calculator and engine displacement calculator.

Pulse per mile and vehicle speed sensor

The pulse per mile (PPM) is the number of electronic signal pulses a vehicle’s speed sensor generates per mile traveled. This value is used in several vehicle sensors, especially now that our cars are equipped with onboard computers.

The number of pulses is computed by a vehicle speed sensor (VSS), which is usually located on the transmission output shaft, transfer case, or driveshaft. The VSS reads the drivetrain rotation downstream of the differential, measuring the average rotational speed of the driven wheels. It does this by counting the electrical pulses generated by the rotation of the reluctor ring/wheel, which produces a fixed number of pulses per revolution.

The pulse per mile formula

To determine the pulse per mile, firstly, we need to calculate the wheel rotation per mile (WRM). This parameter can be derived using the following equation:

WRM=63,360π×TD\mathrm{WRM} = \frac{63{,}360}{\pi\times \mathrm{TD}}

where:

  • WRM\mathrm{WRM} — Wheel rotation per mile;
  • 63,36063{,}360 — Number of inches in one mile; and
  • TD\mathrm{TD} — Tire diameter in inches.

Now that you know the wheel rotations per mile, we can substitute this value in the pulse per mile formula:

PPM=WRM×AR×NT\mathrm{PPM} = \mathrm{WRM}\times\mathrm{AR}\times\mathrm{NT}

where:

  • PPM\mathrm{PPM} — Number of pulses per mile;
  • AR\mathrm{AR} — Axle ratio; and
  • NT\mathrm{NT} — Number of teeth of the reluctor gear ring.

Here, the axle ratio or gear ratio is the number of times the driveshaft turns for one turn of the axle. For instance, an axle ratio of 3.733.73 means the driveshaft spins 3.733.73 times per wheel revolution. You can learn more about gear ratio by accessing our gear ratio calculator.

Moreover, the number of teeth parameter is used to compute the PPM by converting the driveshaft revolutions into electrical pulses, since each tooth passing the sensor produces one pulse.

The pulse per mile calculator: an example

Let’s show you, with an example, how simple and intuitive our calculator is. Suppose that you want to compute the pulse per mile for your sedan car, considering the following parameters:

  • Axle ratio=3.42\mathrm{Axle\,ratio} = 3.42;
  • Number of teeth=20\mathrm{Number\,of\,teeth} = 20; and
  • Tire diameter=26 inches\mathrm{Tire\,diameter} = 26 \, \mathrm{inches}.

Then, you just need to substitute these values into our calculator to find that:

  • Wheel rotation per mile=775.7\mathrm{Wheel\,rotation\,per\,mile} = 775.7; and
  • Pulse per mile=53,058\mathrm{Pulse\,per\,mile} = 53{,}058

Now this number can be used on your odometer, for instance, to read the correct distance you traveled. The odometer will count the pulses from the vehicle speed sensor, and when it reaches the PPM value, you have traveled one mile.

FAQs

What is a VSS?

VSS is a short word for vehicle speed sensor. This sensor detects wheel or transmission rotations. It differs from the so-called wheel speed sensor (WSS), which measures the rotation of an individual wheel.

Therefore, the main difference is that VSS provides the vehicle’s overall speed, whereas the wheel sensors provide four speed values, one per wheel.

Where is the vehicle speed sensor located?

The vehicle speed sensor can be located on the transmission output shaft, transfer case, or driveshaft. Its main function is to read the drivetrain’s rotation downstream of the differential.

The vehicle speed data feeds the speedometer, odometer, cruise control, and transmission shift logic.

What is axle ratio​?

The axle ratio, also known as the differential ratio or gear ratio, indicates how many times the driveshaft turns for one complete revolution of the wheel/axle. This parameter is usually rated in three categories:

  • High gearing (between 2.5 and 3.2);
  • Balanced (between 3.2 and 3.7); and
  • Low gearing (>3.7).

Higher axle ratios mean you will have more torque and acceleration, but worse fuel economy.

How can I calculate the pulses per mile for a 4L60E?

A 4L60E transmission means you are considering a 40-tooth reluctor. You can compute the number of pulses per mile by following the steps below:

  1. Take the axle ratio: AR = 3.42.

  2. Note the tire diameter: TD = 28 inches.

  3. Count the number of the teeth of your reluctor: NT = 40.

  4. Substitute these values in the pulse per mile formula:

    PPM = 63,360/(π × TD) × AR × NT = 98,536

  5. Or you can simply use a pulse per mile calculator.