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SOP 1

Recommended Standard Operating Procedure

for

Calibration Certificate Preparation

1 Introduction

Calibration certificates are the visible outputs of the calibration laboratory that must 

be prepared with utmost care to ensure that they accurately convey all information 

pertaining to a calibration so that data may be used with maximum benefit by all 

concerned. Carefully prepared calibration certificates must contain or refer to all 

information necessary to justify the measurement results and must be thoroughly 

reviewed and authorized prior to release.

A detailed reporting of results is preferred and often required by customers in 

accredited and recognized laboratory systems, which includes a complete narrative 

describing and documenting the calibration, including those for special calibrations 

or tests. According to the ISO/IEC 170251 standard, calibration results may be 

reported in a simplified way when agreed to by the customer. For weights and 

measures (legal metrology applications) reporting of elements of metrological 

traceability for reference to the International System of Units (SI), measurement 

results, and uncertainty results continue to be required with few exceptions2. All

information not provided to the customer must be maintained by the laboratory and 

readily available.

The laboratory is responsible for all information provided within the calibration 

certificate, except for information that was provided by the customer. When 

information is provided by the customer, it shall be clearly identified. The 

calibration certificate will include a disclaimer notifying users that information 

supplied by the customer can affect the validity of results. When sampling is 

provided by the customer (e.g., the method sampling stage), the calibration 

certificate shall state that the results apply to the sample as received from the 

customer. 

2 Content of calibration certificates. 

Regardless of the final form, the calibration certificate must contain the basic information 

described in this procedure (see also Section 7.8 of ISO/IEC 17025 and the attached 

template Calibration Certificate Review Checklist, Appendix B).

Each calibration certificate, supplied in hard copy or electronic format, shall contain the 

following information to minimize the possibility of misunderstanding or misuse:

 1 ISO/IEC 17025:2017, General Requirements for the Competence of Testing and Calibration Laboratories. 2 See GMP 13, Ensuring Traceability, ISO/IEC 17025, Annex A, and International Laboratory Accreditation 

Cooperation (ILAC) and accreditation body policies. 
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Title (e.g., “Calibration Certificate”).

Name and address of the laboratory where the calibration is performed (e.g., 

permanent facility), including any alternative location where a calibration is 

performed (e.g., temporary, mobile, or alternative facility).

Unique identification that all calibration certificate components are recognized, and 

an identification on each page to ensure that the page is recognized as part of the 

complete document, and a clear identification of the end of the certificate. A unique 

calibration number and page X of Y formatting are frequently used to uniquely 

identify the components of a calibration certificate.

Customer name and contact information.

Method used –Cite the Standard Operating Procedure (SOP), including the full title 

or description and the version date. In the absence of a nationally or internationally 

published SOP, a brief but informative description of the methodology shall be 

included. When a customer approves of an addition, deviation, or exclusion from 

the published method, these departures shall also be included 

Unambiguous identification and description of the calibration artifact, and when 

necessary, the condition of the item. Serial numbers are assigned to items by the 

customer, laboratory, or manufacturer to facilitate the internal control of the item 

during the calibration process and subsequent use by the customer. Unique 

identification is verified when an item is submitted to the laboratory for calibration. 

Date(s) of:

• Calibration item receipt;

• Sampling, where critical to the validity and application of the results; 

• Calibration or laboratory activity performance; and

• Certificate issuance.

Cite the sampling plan and methods used. Uniquely identify the items sampled. 

Include the: 

• The date and location of sampling;

• Environmental conditions during sampling that affect the interpretation of 

results; and

• Information related to the measurement uncertainty, where relevant.

Calibration results and corresponding units of measurement are clearly organized 

in a tabular or other convenient format. When a calibration item has been repaired 

or adjusted, the calibration results before and after repair or adjustment shall be 

reported. The measurement units reported are typically related to the nominal value 
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of the calibration item. Measurement units may be selected to reflect an industry 

practice or a customer request.

A statement of the measurement uncertainty, and corresponding measurement unit, 

coverage factor, and estimated confidence interval shall accompany the 

measurement result. The measurement uncertainty is reported in the same 

measurement units as the measurement result (e.g., multiple or submultiple). 

Special care shall be used when the coverage factor is not consistent for all

calibrated items. The results table should be formatted to clearly identify individual 

coverage factors when variations exist (e.g., an additional column containing the 

corresponding coverage factors). When appropriate, significant uncertainty 

components and the rationale for their inclusion are included. Note: the use of 

standard industry practices or reporting units based on customer requests is 

permitted.

Environmental or other conditions under which the calibrations were made that 

influence the measurement results.

Clearly identify the person(s) performing the calibration and authorizing calibration 

certificate by stating their corresponding name, title, and signature. Each authorized 

signatory accepts responsibility for the technical accuracy and validity of the 

reported results.

A statement to the effect that the results relate only to the items calibrated or 

sampled.

A statement identifying how the measurements are metrologically traceable (e.g., 

the laboratory establishes metrological traceability to the International System of 

Units (SI) and is recognized by NIST OWM). The inclusion of supplemental 

supporting information may be requested by the customer.

When statement of compliance or non-compliance with requirements and/or 

specifications (e.g., a conformity assessment), where relevant. Compliance refers 

to an assessment of all criteria of a referenced documentary standard and not a 

limited assessment of a portion or specific clauses (e.g., compliance to all 

specifications versus only the tolerance specification). When a statement of 

conformity is made, the laboratory must clearly identify to which results the 

statement of conformity applies (e.g., all results or a specific portion of the results), 

which specifications, standards or parts thereof are met or not met, and the decision 

rule applied (unless the decision rule is inherent in the specification or documentary 

standard). When a statement of conformity to a specification or documentary 

standard is made, the laboratory shall document the decision rule applied, take into 

account the level of risk associated with the decision rule employed (such as false 

accept, false reject, and statistical assumptions), and apply the decision rule. Where 

decision rules regarding uncertainties and tolerances are not part of the 

documentary standard, decision rules will be agreed to by the customer and reported 

on the calibration certificate. 
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Opinions and interpretations, where appropriate and needed, shall be based on the 

measurement results, clearly stated, and identified as such. Only technically 

competent laboratory personnel are permitted to express opinions and 

interpretations (e.g., an authorized signatory). When opinions and interpretations 

are directly communicated and discussed with the customer, a record of the 

conversation shall be documented and retained. 

Results from external providers shall be clearly identified. 

Additional information which may be required by specifications, specific methods,

customers, or groups of customers.

To ensure parts of the calibration certificate results are not taken out of context, a 

statement specifying that the calibration certificate shall not be reproduced except 

in full, without written approval of the laboratory may be included.

A calibration certificate or calibration label shall not include any recommended 

calibration interval, except when required for legal applications or where requested 

and agreed to by the customer. 

3 Review and Issue to Customer.

A thorough technical and quality review of each calibration certificate should be 

conducted according to laboratory Quality Management System before issuance to 

prevent errors, recall, and certificate amendment.

Review measurement units and symbols according to the current edition of NIST 

Special Publication (SP 811), The NIST Guide for the Use of the International 

System of Units (https://www.nist.gov/physical-measurement-laboratory/specialpublication-811). 

The template Calibration Certificate Review Checklist may be used by the 

laboratory to aid in multiple evaluation functions (Appendix B).

Review each calibration certificates before issue to the customer to ensure 

it meets the requirements of this procedure.

Review external calibration certificates during the supplier evaluation

process.

Review issued and/or template calibration certificates during a technical or 

quality audit. 

4 Calibration Certificate Amendment. 

When a calibration certificate issued to a customer must be changed, amended, or 

re-issued, the changed information shall be clearly identified. The reason for the 

change shall be included in the report, when appropriate. 
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Amendments made after issue to the customer shall be made only in the form of a 

further document or data transfer, which includes the statement “Amendment to 

Calibration Certificate” or an equivalent form of wording.

When it is necessary to issue a completely new calibration certificate, it shall be 

uniquely identified and contain a reference to the original calibration certificate that 

it replaces.

Amended calibration certificates shall meet all the requirements of this procedure.

5 Records

The laboratory shall file, organize, and retain all calibration certificates in a 

systematic manner for ease of retrieval.

Retain legible copies of all issued and amended calibration certificates according 

to the laboratory Quality Management System. 
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Appendix A – Example Certificate

COMPLIANT CALIBRATION LABORATORY

123 Some Ave.

City, State Mail code

XYZ Accreditation Body: 1234567890

CALIBRATION CERTIFICATE

FOR

1 kg to 10 mg kit

(Twenty-one weights)

Manufacturer: DENTROM LAKE

Serial No.: 27269

SUBMITTED BY:

YOUR CUSTOMER, INC.

Customer’s Address

City, State Zip code

Phone/Email

Nominal

(g)

Conventional Mass

(g)

Conventional Mass3

Correction

(mg)

Expanded

Uncertainty

(mg)

ASTM Class 4

Tolerances

(mg)

1000 1000.000 82 0.82 0.92 20

 500 500.000 71 0.71 0.53 10

 300 299.999 87 - 0.13 0.27 6.0

 200 200.000 67 0.67 0.18 4.0

 100 100.000 411 0.411 0.091 2.0

 50 50.000 318 0.318 0.051 1.2

 30 30.000 117 0.117 0.028 0.90

 20 19.999 987 - 0.013 0.023 0.70

 10 10.000 011 0.011 0.018 0.50

 5 5.000 022 0.022 0.015 0.36

 3 3.000 112 0.112 0.013 0.30

 2 1.999 965 - 0.035 0.012 0.26

 1 1.000 117 0.117 0.010 0.20

 0.500 0.500 013 2 0.013 2 0.005 1 0.16

 0.300 0.300 022 3 0.022 3 0.004 8 0.14

 0.200 0.200 001 7 0.001 7 0.004 3 0.12

 0.100 0.100 001 3 0.001 3 0.004 2 0.10

 0.050 0.050 001 8 0.001 8 0.004 0 0.085

 0.030 0.030 001 1 0.001 1 0.003 7 0.075

 0.020 0.020 000 9 0.000 9 0.003 3 0.070

 0.010 0.009 999 7 - 0.000 3 0.003 1 0.060

The data in the above table applies only to those items specifically listed on this calibration certificate.

Uncertainty Statement: 

The combined standard uncertainty includes the standard uncertainty reported for the standard, the standard uncertainty for the 

measurement process, the standard uncertainty for any uncorrected errors associated with buoyancy corrections, and a component 

of uncertainty to account for any observed deviations from NIST values that are less than surveillance limits. The combined 

standard uncertainty is multiplied by a coverage factor (k) of 2 to provide an expanded uncertainty, which defines a level of 

confidence of approximately 95 percent (95.45 %). The expanded uncertainty presented in this report is consistent with the ISO/IEC

 3 Conventional Mass: The conventional value of the result of weighing a body in air is equal to the mass of a standard, at reference density 8.0 

g/cm3, at a reference temperature 20 °C, which balances this body at this reference temperature in normal air density 0.0012 g/cm3

. See OIML 

D28 (2004), “Conventional value of the result of weighing in air.”

Calibration No.: TI-01-056

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Guide to the Expression of Uncertainty in Measurement (2008). The expanded uncertainty is not to be confused with a tolerance 

limit for the user during application.

Traceability Statement: 

The Standards of the Compliant Calibration Laboratory are traceable to the International System of Units (SI) through the National 

Institute of Standards and Technology, and are part of a comprehensive measurement assurance program for ensuring continued 

accuracy and measurement traceability within the level of uncertainty reported by this laboratory. The unique laboratory calibration 

number identified above shall be used in referencing metrological traceability for artifacts identified only in this certificate.

Conformity Assessment:

The weights submitted for this calibration were marked as ASTM Class 4. ASTM E617 (2018), Standard Specification for 

Laboratory Weights and Precision Mass Standards, was used to evaluate these weights. Weights fully comply with all 

requirements (both specifications and tolerances) of this documentary standard. Stated expanded uncertainties are less than onethird of the specified tolerances (maximum permissible errors, m.p.e.) and the mass value plus or minus the expanded uncertainty 

is within the stated tolerances.

Supplemental Information:

Description of Artifacts Submitted for Calibration:

Twenty one weights from 1 kg to 10 mg, marked ASTM E617 Class 4. Weights from 1 kg to 1 g: two-piece weights, with assumed 

density of 8.0 g/cm3. Weights from 500 mg to 50 mg: sheet weights, with assumed density of 16.6 g/cm3. Weights from 30 mg to 

10 mg: sheet weights, with assumed density of 2.7 g/cm3.

Conditions of Artifacts Submitted for Calibration:

Artifacts showed evidence of improper handling. Fingerprints and dents were visible on the surface of the weights.

Treatment of Artifacts Prior to Calibration:

Artifacts were cleaned with cheesecloth and ethyl alcohol. Thermal equilibrium time/conditions: seven days next to balances in 

mass laboratory.

Procedure Used:

Double Substitution (NISTIR 6969, SOP 4, 2019)

Environmental Conditions at Time of Calibration:

Temperature: 20.1 °C to 20.2 °C Barometric Pressure: 752.7 mmHg Relative Humidity: 43.35 % to 

43.40 %

Date Artifacts Received: January 5, 2019 Date Certificate Issued: January 13, 2019

Date of Calibration: January 12, 2019

Due Date (Requested by Customer): January 15, 2019

Josh Balani II

Calibration Performed by: Josh Balani II, Metrologist

This document does not represent or imply endorsement by the Accreditation Body of Compliant Calibration Laboratory or any agency of a state 

and/or national government. This document may not be reproduced, except in full, without the written permission of the Compliant Calibration 

Laboratory.

Calibration No.: TI-01-056

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Appendix B - Calibration Certificate Review Checklist

ISO/IEC 17025:2017, Section 7.8 - Reporting of Results

This evaluation form may be used as an assessment tool for calibration certificates. Its use needs to include 

objective evidence of the assessment (e.g., a marked-up certificate).

Criteria Guide Compliance

7.8.1.2

Reported accurately, clearly, unambiguously and objectively; in accordance with method 

instructions; include all info requested by customer, necessary for interpretation of the results, & 

required by the method

Calibration Certificate Core Requirements (Include at least the following information, unless valid reasons for 

not)

7.8.2.1 a) Title

7.8.2.1 b, c) Laboratory name & address and location where tests/calibrations performed

7.8.2.1 d)

Unique identification making all the portions of the certificate uniquely identifiable. Clearly 

indicate document end (a way to recognize a complete report). For Example: page number and total 

number of pages (X of Y)

7.8.2.1 e) Customer name and contact information

7.8.2.1 f, n) Identify method used; additions, deviations, exclusions from the method

7.8.2.1 g) Description and unambiguous identification of the item(s) calibrated and when necessary condition

7.8.2.1 h-j) Dates: receipt, sampling if applicable, date(s) of performance of lab activity, certificate issue

7.8.2.1 k) Reference to sampling plan and procedures used where relevant to validity or application of results

7.8.2.1 l) Statement to the effect that the results relate only to the calibrated items

Note: Recommend statement shall not be reproduced except in full, without written lab approval

7.8.2.1 m) Calibration results with appropriate units of measurement, where appropriate

7.8.2.1 o) Name(s), function(s) & signature(s) or equivalent ID of person(s) authorizing the certificate

Calibration Certificates (In addition to 7.8.2.1)

7.8.4.1 a) Uncertainty of the measurement result in the same unit as that of the measured item, or unit relative 

to item

7.8.4.1 b) Calibration conditions (e.g., environmental) that influence the measurement results

7.8.4.1 c) Statement on how the measurements are metrologically traceable

7.8.4.1 d) Before and after measurement results when adjustment or repair is made

7.8.4.1 e), 

7.8.6

If compliance statement is made: Identify to which results they apply, clauses met/not met, and 

account for the decision rule (e.g., uncertainty)

7.8.4.3 No calibration interval on certificate/label except if customer agrees (superseded by legal 

regulations)

Conformity Assessment (7.8.6) 

7.8.6 Decision rule documented in procedure or by customer; statement identifies which results are 

applicable and which portions of the documentary standard were or were not assessed 

Sampling (7.8.5) Specific requirements noted in 7.8.3.2, 7.8.4.2

7.8.5 a-f) Sampling date, unique identify, material or product, location, diagrams, sketches, photographs; 

reference plan & procedures; environmental conditions; information for uncertainty evaluation

Opinions and Interpretations

7.8.4.1. f)

7.8.7

Document basis of opinions and interpretations when included with reference to basis, performed 

by authorized personnel only; clearly identify

Amendments 

7.8.8 Amendments after issue made as further document/data transfer with statement, meet all 

requirements. New certificate is uniquely identified, and reference to the original that it replaces
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Appendix C - Calibration Certificate Review Checklist

ISO/IEC 17025:2017, Section 7.8 - Reporting of Results

This evaluation form may be used as an assessment tool for evaluating multiple calibration certificates; for example, 

during an internal audit or during review of proficiency testing certificates. Its use needs to include objective 

evidence of the assessment (marked-up certificates).

X = Nonconformity C = Comment

Lab Names or 

Parameters:

7.8.1.2

Calibration Certificate Core Requirements (Include at least the following information, unless valid reasons for not)

7.8.2.1 a)

7.8.2.1 b, c)

7.8.2.1 d)

7.8.2.1 e)

7.8.2.1 f, n)

7.8.2.1 g)

7.8.2.1 h-j)

7.8.2.1 k)

7.8.2.1 l)

7.8.2.1 m)

7.8.2.1 o)

Calibration Certificates (In addition to 7.8.2.1)

7.8.4.1 a)

7.8.4.1 b)

7.8.4.1 c)

7.8.4.1 d) 

7.8.4.1 e), 7.8.6

7.8.4.3

Conformity Assessment (7.8.6)

7.8.6

Sampling (7.8.5) Specific requirements noted in 7.8.3.2, 7.8.4.2

7.8.5 a-f)

Opinions and Interpretations

7.8.4.1. f), 7.8.7

Amendments to Test Reports and Calibration Certificates

7.8.8

* Participants that apply tolerances
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