As Found versus As left

One of the most common questions is understanding the difference of as found versus as left data on a certificate of calibration. First and foremost, these terms apply to data – not to the instrument condition. Many quality professionals get confused because these terms are often used interchangeably. These terms each refer to a specific time when the measurements are recorded. These records are necessary to determine degree of change and for quality tracking.

Defining As Found versus As Left

As Found

The as found term refers to measurement data recorded prior to repair or adjustment. This may also be called before data or received data. As found is only used to describe measurements from an item that must be repaired or adjusted to ensure accuracy.

As Left

The term as left describes measurement data recorded after repair or adjustment. As left is often used interchangeably with the phrase after data. The as left measurement data provides validation for necessary repairs or adjustments.

Found Left

A found left term is appropriate when measurement data is recorded for an item that does not require adjustment or repair. The term found left is only used for instruments that passed testing without modification.


The inoperable term is used when an instrument is incapable of being powered on or unusable to test a specific range or function.

Comparing Historical Data

Quality professionals may track calibration data over time for many different reasons. Quality management systems may require a record of test findings or the organization may want to monitor the data trends over time. Managers can use the information to determine if a certain instrument is losing accuracy over a given period or looking at conformance as a whole. This information can help quality departments make decisions about testing or tooling investments.

Example: torque wrench #003 tends to be out of calibration by more than 10% after the most recent test. The Quality Manager checks past history and finds that #003 has been testing out of calibration at a greater rate over the past 3 cycles. This may prompt to manager to shorten the calibration interval or begin planning for replacement of the wrench.Looking for a visual way to explain each data term? Access the Data Term Infographic