Calibration Frequency Of Measuring Instruments

One of the most confusing questions for professionals working in any pharmaceutical industry or area where measurements are involved is, What should be the calibration frequency?or When equipment or instruments should be calibrated?

In this article, we will discuss the following important points.

  • What is calibration?
  • Importance Of Calibration?
  • When To Perform Calibration?
  • How is Initial Calibration Frequency determined?
  • What is the traditional method used to determine calibration duration?
  • How Final Calibration frequency or due date is determined?
  • When Calibration Frequency Can Be Decreased.
  • When Calibration Frequency Can Be Increased.

What Is Calibration?

Calibration is the process in which the values of any device or instrument are compared with reference standards whose values are accurate & known.


  • Take a simple example of calibration of analytical balance used in a quality control laboratory.
  • To calibrate the balance we place standard weights on the balances & readings are recorded.
  • If The reading displayed on balance is the same as the value of the reference standard weight then we declare that our balance is calibrated.

Importance Of Calibration

The importance of calibration can not be ignored because of the following important facts,


The critical operations which involve measurements are greatly dependent on the accuracy of the measuring device.If the device is calibrated we can claim that our results are accurate.

Product Quality

If a product is manufactured using calibrated measuring devices it assures us that our product is of high quality.

Precise Results

By using calibrated devices we get precise results.

Reduce Cost

By using timely validated devices the down times are reduced (which may occur due to faulty readings) & cost of operation is also reduced.

When To Perform Calibration?

  • Before first time usage of a new device or instrument.
  • After the due date, recalibration is done.
  • According to the specifications of manufacturer.
  • To meet the requirements of  regulatory bodies.
  • In case of any shock or damage.

What Is Calibration Frequency?

Calibration frequency is the duration after which the device or instrument is recalibrated.

Calibration frequency is also known as Calibration Interval Or Calibration Due Date.


The general concept is that Calibration frequency is the due date which is provided by the third party and after which the device or instrument is calibrated.

This concept is wrong because the third party can not provide a due date. After all, determining the due date or calibration interval is the responsibility of the customer.

The logic behind this point is that, at the customer site the calibration status may be changed due to any shock,  damage or unsuitable conditions so Calibration Frequency as Per ISO 17025 states that,

The third-party which provides calibration services should not mention the due date or calibration interval on the certificate or the calibration label until & unless there is a mutual understanding with the customer.

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How To Determine Calibration Frequency?

Now we will discuss how calibration interval or calibration frequency is determined Or in simple words how an organisation sets a calibration duration for a device or equipment.

We will divide it into 2 parts,

  • Initial Calibration Interval
  • Final Calibration Interval

Initial Calibration Interval

Initial calibration interval or frequency is the period which is set for the first time for any instrument or device.

Most Pharmaceutical industries use ls traditional fixed initial calibration intervals like

  • Bi-Annual
  • Annual
  • After Two Years

Some Pharma uses one year as an initial calibration frequency for those devices which are used for less critical operations & twice a year for those which are used for critical processes.

Best Practice

The best practice to determine calibration interval is based on the following,

  • It is initially defined based on expert advice.
  • It is defined based on previous experience with such an instrument.
  • Based on manufacturer recommendations.
  • Based on regulatory requirements.
  • Nature of work for which it is used.
  • Frequency of use.

Final Calibration Interval

The initial calibration frequency is not final; it is set only to get data for a specific period.

When we have sufficient calibration data for a specific device we compare different values of past data and check the trend of values or results.

If all the values are within the limit from start to end we may increase the initial validation duration.

If values show variation we may decrease the duration.

When  Calibration Frequency Can Be Decreased?

As calibration is performed by third parties it increases the cost of the organisation so here we will discuss the cases where the calibration frequency can be decreased to reduce the cost & men power involved.

The calibration frequency can be decreased in following situations.

  • When the tolerance of calibration results is within range.
  • When the device or equipment is used for less sensitive or non-critical operations.

When  Calibration Frequency Can Be Increased?

Can be increased in the following cases,

  • When the drift of a device or instrument is out of defined ranges.
  • When the device shows significant drift in past results.
  • When the device is placed in a critical area.
  • When the results of a device may significantly affect the product quality.
  • When the equipment is used in an area where temperature, humidity or vibrations may affect the performance.

Also Read

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  3. Difference between Validation & Calibration.
  4. Why is a Separate Manufacturing Facility Required For Penicillin And Non Penicillin Products
  5. Why Do We Use Three Batches For Validation
  6. GMP vs cGMP and 21 CFR.
  7. Qualification|FAT|SAT|DQ|IQ|OQ|PQ