# Pulse per Mile Calculator

URL: https://speedycalculator.com/calculators/everyday-life/pulse-per-mile/
Last updated: 2026-10-25

> The pulse per mile calculator works out the pulses per mile (PPM) a vehicle speed sensor sends, from the tyre diameter, axle ratio and the number of teeth on the reluctor (tone) ring, for calibrating speedometers.

## Inputs

- Tyre diameter (in, cm, mm, ft, m)
- Axle ratio
- Reluctor teeth

## Results

- Wheel revolutions per mile
- Pulses per mile
- Pulses per kilometre

## Formula

```
Wheel revolutions per mile = 63,360 ÷ (π × tyre diameter in inches)
PPM = revolutions per mile × axle ratio × reluctor teeth
```

## Explanation

Electronic speedometers and engine computers count pulses from a speed sensor on the transmission output or differential. After changing tyre size or axle gears, the PPM must be recalibrated or the speedometer and odometer will read wrong.

### How to use the Pulse per Mile Calculator

- **Tyre diameter**
- **Axle ratio**
- **Reluctor teeth**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter the tyre's overall diameter, the axle (final-drive) ratio and the number of teeth on the reluctor ring.

### Tips

- Use your own measured figures – fuel economy, speed and prices vary a lot with driving style, traffic, load and season.
- Pick the unit in each field's menu (miles or kilometres, mpg or L/100 km); the calculator converts everything for you.
- Fill up to the brim twice and divide the distance by the fuel added to measure real fuel economy.
- For vehicle modifications, treat results as a starting point and confirm with the parts maker or a professional mechanic.

### Common mistakes to avoid

- Mixing US and imperial (UK) gallons – a UK gallon is about 20% bigger.
- Using the advertised fuel economy instead of real-world figures.
- Forgetting tolls, parking and wear and tear when comparing driving with public transport.

### Inputs explained

FieldWhat to enterTyre diameterUnits: in, cm, mm, ft, mAxle ratioA numberReluctor teethA number

### What each result means

- **Wheel revolutions per mile** = 1609.344÷(pi×[Tyre diameter])
- **Pulses per mile** = [Wheel revolutions per mile]×[Axle ratio]×[Reluctor teeth]
- **Pulses per kilometre** = [Pulses per mile]÷1.609344

### Example values

How the main result changes when **Tyre diameter** changes and everything else stays at the example values above:

Tyre diameter (in)Pulses per mile14214,93421143,29028107,4673585,9744271,6455653,734

## Worked example

Inputs — Tyre diameter: 28 in; Axle ratio: 3.73; Reluctor teeth: 40.

Results — Wheel revolutions per mile = 720.3; **Pulses per mile = 107,467**; Pulses per kilometre = 66,777.

## FAQ

**Why recalibrate after a tyre change?**
Bigger tyres turn fewer times per mile, so the speedometer reads low unless the PPM is updated.

**What is the standard PPM?**
Many GM vehicles use 4,000 PPM at the output; other makes use different values.

**Where do I find the reluctor teeth count?**
In the service manual, or by counting teeth on the tone ring.

**What formula does the Pulse per Mile Calculator use?**
Wheel revolutions per mile = 63,360 ÷ (π × tyre diameter in inches).