How To Read An Odometer

Understanding how the odometer works and reads is one aspect overlooked by automobile owners. When you set out on a ride with your automobile, you wonder how long it will take to arrive at your destination. This is especially true when you are journeying through an unaccustomed road. 

However, it is often challenging to tell exactly what time your ride will reach its destination. This is because your driving time is influenced by how good the road is as well as its traffic. But, the good news is you can tell what distance is left to reach your destination. This is why you have an odometer in your automobile.

The odometer is an important part of your automobile. It bears certain information useful to both car and bike owners and second-hand automobile dealers. Thus, we will look at what the odometer is, how it works, how it reads, and other benefit questions.

What Is An Odometer

An odometer is a device on an automobile that counts the miles it has traveled. You will find it on your vehicle’s dashboard where the speedometer lies. Some countries call it the odograph and others know it as a milometer. The odometer can be electronic or mechanical. In some cases it is electromechanical. 

The odometer not only measures the covered miles by a traveling vehicle but also helps dealers of used cars. The buyer had seen the mileage on the odometer decides if a car is good for its price.

The odometer also has other useful attributes. For one, Its mileage can help you know when your vehicle needs its routine check. You can also use the odometer to determine how much fuel your vehicle consumes. If you know the actual distance of your journey, the odometer can help you tell what’s remaining in the journey.

How Accurate Is A Vehicle Odometer Reading

The miles counted and recorded by the car’s odometer increase with every ride. To maintain the odometer accuracy, there are ongoing calculations in the inner workings of your vehicle. This is especially true for new vehicles. Occasionally, the odometer readings may be inaccurate. 

This is often associated with changing your vehicle’s engine and not readjusting the computer. When the computer is not recalibrated after an engine change, it continues measuring based on the old engine. This disparity causes the odometer reading to be faulted and inaccurate.

You should also know that the GPS can affect the correctness of the odometer. This usually happens when the GPS loses its connection and regains it like when driving through a closed route. During this period the odometer may give an inaccurate result. It may not record the full distance covered by the vehicle.

How Does The Odometer Calculate The Distance Of The Ride

Oftentimes, in a new model vehicle, the odometer performs its function by recording the rotation of the wheel. The miles covered is gotten by multiplying the circumference of the tire by the number of wheel rotation. You determine the circumference of the tire by multiplying its diameter by 3.1416(Pie). Not to worry though, you won’t be doing these calculations. They are automated by the vehicle. Errors arise in the odometer readings when you have a substandard tire or one that is worn.

You can also calculate the exact distance covered by first subtracting the former odometer reading from the new one. And, dividing the actual tire diameter by what the standard is. Then, multiply both results.

Formula is; {(Final odometer reading) – (initial odometer reading)} X {(actual tire diameter) ÷ (standard tire diameter)}. But, you should know that knowing how the odometer works are more than this. 

How Does The Odometer Work

With each passing season, the automobile industry evolves. Vehicles now have higher performance and beautiful designs. However, how the odometer works have more or less remained the same. Vehicles keep a record of their mileage either mechanically or electronically. The odometer has been made such that every kilometer moved by a vehicle has a tallying wheel rotation. This count is usually constant for standard car wheels. 

Elements of the odometer include the wheel sensor, odometer drive, and screen. The wheel sensor is most times located close to one of the front wheels. The sensor can also be in the gearbox depending on the odometer’s model. Thus, the measurement will follow through based on where the sensor is. The odometer drive functions to read the speed indicator and transfer it to the engine control unit. The screen shows what was calculated by the control unit based on the wheel’s rotation.

Mechanical Odometer

For the mechanical odometer, work begins at the transmission. Here, its transmission system has a minute gear installed into it. The gear functions to advance the odometer. The gear and the drive cable of the speedometer are linked together on one end. The cable then joins to the instrument cluster on its other side.  

With a turned-on engine of a moving vehicle, the internal transmission gear is turned too. The flow of the internal transmission gear is linked by the drive cable to another group of gears connected to changeable numbers. 

The count begins from the first digit on the far right of the group of numbers. The count continues until the digit reaches its highest possible number for the distance traveled by the vehicle. This causes a rollover to the left digit. This process continues until all digits reach their highest value. When this occurs they reset to number zero and the counting starts all over. The numbers on the mechanical odometer may sometimes get slightly displaced.

Electronic Odometer

These odometers are newer inventions. They depend on the car’s electronic activity to measure the correct mileage. Similar to the mechanical odometers, they use gear to alter the count on the dashboard. However, instead of a drive cable, they use a magnetic sensor to determine how much the gear turns in the transmission. The gotten signal is then transmitted to the ECU by a set of wires. The ECU interprets the signal and converts it to a mileage count.

One advantage it has over the mechanical odometer is its better accuracy. This is because the electronic odometer is not easily rigged. They often give the correct mileage count of the automobile. The presence of the digital form of this odometer in a vehicle makes it a better choice for purchase. Especially when dealing with used vehicles.

Additionally, odometers have a trip meter. This trip meter can help the driver know the mileage of a distance without looking at the actual odometer.

Can An Odometer Reading Be Changed

Yes, an odometer reading can be changed. A car dealer may reset a vehicle mileage to something lower just to increase the car’s price. So, how then can you know if an odometer has been reset? Below are tips to help.

a. You can ask your mechanic or any trained automobile technician to come to check the vehicle mileage before you buy. 

b. Check the car’s maintenance history and gather information about the vehicle with its VIN.

c. Listen for odometer clicking. 

What Is The Importance Of An Odometer In A Vehicle

The main aim of the odometer is to measure the distance a car traveled. It also estimates the value of a vehicle. It also plays a role in performing routine vehicle maintenance.


The odometer is a vital part of the vehicle. Either a mechanical or an electronic odometer is installed in a vehicle. Both measure the traveling distance of a vehicle using special technology.