What Is an Odometer on a Car?

An odometer is the instrument that records a vehicle’s total distance traveled since it was built, typically displayed in miles or kilometers on the dashboard. It’s used for maintenance scheduling, resale valuation, warranty coverage, and legal recordkeeping, and it cannot legally be reset except during documented repairs.

How an Odometer Works

Odometers count distance by measuring wheel rotation and translating it into mileage or kilometers. In older vehicles, a mechanical gear train drives rolling number wheels. In modern cars, electronic sensors feed data to a control unit that calculates distance and stores the total in non-volatile memory, then displays it digitally. Tire size, wear, and calibration can subtly affect accuracy.

Mechanical Odometers

Mechanical units use a cable driven by the transmission or wheel hub to turn a series of gears that advance numbered drums. They are robust but can show telltale misalignment if tampered with and are more sensitive to wear and cable faults.

Electronic/Digital Odometers

Digital systems read wheel-speed or transmission sensors, compute distance via the vehicle’s computer, and store the cumulative total in protected memory (often in the instrument cluster, body control module, or powertrain control module). Many systems include anti-tamper checks and cross-verification over the CAN bus. If a cluster is replaced, manufacturers require programming the correct mileage and labeling the vehicle’s records accordingly.

Types and Related Terms

The terms around odometers can be confusing. Here are the common readouts and how they differ so you know which number matters for legal and maintenance purposes.

• Odometer: The total accumulated distance since the vehicle was manufactured; it is not meant to be reset.
• Trip meter (Trip A/B): A user-resettable counter for tracking the distance of a journey, fuel tank, or service interval.
• Distance-to-empty (DTE): A fuel or battery range estimate; not a distance recorder.
• Hour meter: Tracks engine or drivetrain operating hours (common on heavy equipment and some trucks/boats).
• GPS/app trip logging: Third-party or built-in tools that estimate trip distance; they do not replace the vehicle’s official odometer.

In short, the odometer is the definitive legal and maintenance mileage, while trip meters and range estimates are convenience tools you can reset or ignore without affecting the official record.

Why Odometer Readings Matter

Mileage influences how you maintain your car and how the market values it. It also appears in official documents during ownership transfers and can affect insurance and lease terms.

Below are the most common ways odometer readings are used across a vehicle’s life.

• Maintenance scheduling: Setting intervals for oil changes, tire rotations, timing belts, and EV service checks.
• Warranty coverage: Many warranties expire at a specific mileage, whichever comes first.
• Resale valuation and history: Buyers, dealers, and history services weight mileage heavily; big jumps or inconsistencies raise flags.
• Leasing and rentals: Contracts often include mileage limits and per-mile fees for overages.
• Taxes and expenses: Fleet managers and self-employed drivers may log mileage for reimbursement or tax deductions.
• EV battery warranties: Often defined by years and mileage, whichever comes first.

Because so much rides on it, the odometer is one of the most scrutinized numbers on any vehicle, from routine service to final sale.

Accuracy and Limitations

Automakers typically calibrate odometers to be within a few percentage points of true distance, but real-world variation is normal. Tire diameter (affected by model, inflation, and wear) and aftermarket wheel/tire changes can shift readings slightly. Unlike speedometers, which face strict under-reporting limits in many regions, odometer accuracy is not universally standardized—expect typical error of about 1–3% in ordinary use.

Legal Protections and Tampering

Rolling back or altering an odometer is illegal in many countries. In the United States, federal law (49 U.S.C. Chapter 327) prohibits odometer tampering and requires mileage disclosure at ownership transfer for most vehicles under 16,000 pounds GVWR. Under NHTSA rules (49 CFR Part 580), since January 1, 2021, model year 2011 and newer vehicles require odometer disclosure for 20 years (phased so 2011 models are covered until 2031, 2012 until 2032, and so on). If the instrument cluster is replaced, the repair must be documented and often labeled as “mileage not actual” if exact continuity isn’t possible.

If you’re evaluating a used car, these signs can help you spot possible odometer fraud or errors.

• Wear-and-tear that doesn’t match the mileage (e.g., heavily worn pedals or seats at low readings).
• Service records or inspection reports with inconsistent mileages.
• Digit misalignment on mechanical odometers or display glitches on digital units.
• “Mileage not actual” or “exempt” notes on the title, or a replaced cluster without supporting documentation.
• Car history reports showing mileage reversals or gaps around auction dates.

No single clue is definitive; verify with maintenance documentation, title history, and a professional pre-purchase inspection for confidence.

Practical Tips for Drivers

With a little attention, you can get more value and fewer headaches from your odometer readings.

Use these practices to keep your mileage accurate, useful, and well-documented.

1. Record mileage at each service visit and keep receipts to build a clear history.
2. Use trip meters to track fuel economy and interval-based tasks (like tire rotations).
3. Avoid drastic tire size changes; if you do, know they can affect indicated distance and speed.
4. Learn how to switch units (mi/km) in your settings to match local rules or records.
5. If an instrument cluster fails, have a qualified shop program the correct mileage and document the repair.

Good records and sensible setup make your odometer a trustworthy tool for maintenance, resale, and compliance.

Frequently Asked Questions

Can you reset an odometer?

No. Resetting or rolling back the odometer is illegal. Only trip meters are meant to be reset. If a cluster is replaced, mileage must be programmed or documented according to local law.

Where is the odometer located?

It’s displayed in the instrument cluster behind the steering wheel. On digital dashboards, it appears in the main screen or a sub-menu, often labeled “Odo.”

What units does it display?

Miles or kilometers, depending on the market and settings. Many vehicles allow you to switch units in the infotainment or instrument settings.

Do electric vehicles have odometers?

Yes. EVs track total distance just like combustion cars. The odometer is independent of battery state of charge and may be used for warranty limits and service intervals.

What’s the difference between an odometer and a speedometer?

The speedometer shows how fast you are currently traveling; the odometer accumulates how far you’ve traveled in total.

Summary

An odometer is the official, cumulative distance counter on a vehicle, essential for maintenance, valuation, and legal records. Modern systems compute distance from wheel or transmission sensors and store it in protected memory, while related tools like trip meters are user-resettable for convenience. Because mileage affects warranties, resale, and compliance, odometer tampering is illegal and mileage disclosure is required at sale in many jurisdictions—so keep accurate records and verify history when buying used.

Is 70,000 miles a lot for a 10 year old car?

No, 70,000 miles is generally considered low mileage for a 10-year-old car, as the average driver puts on 12,000-15,000 miles per year, leading to an expected range of 120,000-150,000 miles for a car of that age. However, the overall value and condition of the car depend on the maintenance history, how the miles were accumulated (highway vs. city), and the car’s overall condition, not just the odometer reading. 
What to consider beyond mileage

• Maintenance History: A consistent maintenance record, including oil changes and service, is more important than the mileage alone. 
• Type of Driving: Highway miles are less harsh on a car than city miles, which involve more stop-and-go driving. 
• Vehicle History Report: A report from services like Carfax can show if the car has been in accidents or has any other issues. 
• Overall Condition: Look for wear and tear on the driver’s seat and check for any oil or fluid leaks under the car. 
• Age and Inactivity: Extremely low mileage for a car’s age can sometimes indicate that it sat unused for long periods, which can lead to its own problems. 

In summary
A 10-year-old car with 70,000 miles could be a good find, but always investigate the car’s history and condition to get a complete picture of its overall value and potential.

Is an odometer the same as mileage?

No, an odometer and mileage are not the same; an odometer is the instrument that measures and displays the distance a vehicle has traveled, while mileage refers to the actual total distance itself. The odometer’s reading is how you know the vehicle’s mileage.
 
Odometer

• What it is: A device or system in a vehicle that measures and records the total distance it has been driven. 
• How it works: It can be mechanical (with gears and dials) or digital (using sensors and a computer). 
• Purpose: To track a vehicle’s usage, help with maintenance, determine its resale value, and understand fuel efficiency. 

Mileage

• What it is: The total distance a vehicle has traveled throughout its lifespan. 
• How it’s displayed: It is the number shown on the odometer, which can be in miles or kilometers, depending on the vehicle and country. 
• Significance: A high mileage can indicate heavy use, while a low mileage can suggest a vehicle has been used less. 

In summary, the odometer shows the mileage.

How do I check my car odometer?

To check a car’s odometer, locate the dashboard’s digital display or gauge cluster and turn the ignition to the “accessory” position or “on” (without starting the engine) to view the mileage reading, which is often labeled “ODO” or “Mileage”. You can also find the vehicle’s mileage on its vehicle history report or by using an OBD2 scanner to retrieve data from the car’s computer system.
 
Method 1: Reading the Onboard Odometer

1. Turn the Ignition On: Insert the key and turn it to the “accessory” (ACC) position or the “on” (ON) position without fully starting the engine. 
2. Locate the Dashboard Display: Look at the instrument cluster or gauge cluster for the digital display. 
3. Read the Mileage: The odometer reading will appear as a series of numbers, often labeled “ODO” or “Mileage”. The rightmost digit shows tenths of a mile or kilometer. 

Method 2: Using a Vehicle History Report 

1. Obtain the Vehicle Identification Number (VIN): Opens in new tabThe VIN is a unique 17-character code found on the driver’s side dashboard or on the driver’s side door jamb. 
2. Use a Vehicle History Service: Opens in new tabEnter the VIN into a vehicle history report service (like EpicVIN or VERIFI) to access a record of the car’s mileage history. 

Method 3: Using an OBD2 Scanner 

1. Locate the OBD2 Port: The port is typically found under the dashboard on the driver’s side. 
2. Plug In the Scanner: Connect an OBD2 scanner to the port. 
3. Turn on the Ignition: Turn the key to the “accessory” or “on” position so the scanner can communicate with the car’s computer. 
4. Retrieve Data: Use the scanner’s interface to access and display the odometer reading, which can sometimes be found in modules other than the engine module. 

What does an odometer do in a car?

An odometer or odograph is an instrument used for measuring the distance traveled by a vehicle, such as a bicycle or car. The device may be electronic, mechanical, or a combination of the two (electromechanical).